diff options
| -rw-r--r-- | arch/sh/include/asm/barrier.h | 1 | ||||
| -rw-r--r-- | drivers/virtio/virtio_pci_common.c | 2 | ||||
| -rw-r--r-- | tools/virtio/asm/barrier.h | 22 | ||||
| -rw-r--r-- | tools/virtio/linux/compiler.h | 9 | ||||
| -rw-r--r-- | tools/virtio/linux/kernel.h | 1 | ||||
| -rw-r--r-- | tools/virtio/ringtest/Makefile | 22 | ||||
| -rw-r--r-- | tools/virtio/ringtest/README | 2 | ||||
| -rw-r--r-- | tools/virtio/ringtest/main.c | 366 | ||||
| -rw-r--r-- | tools/virtio/ringtest/main.h | 119 | ||||
| -rw-r--r-- | tools/virtio/ringtest/ring.c | 272 | ||||
| -rwxr-xr-x | tools/virtio/ringtest/run-on-all.sh | 24 | ||||
| -rw-r--r-- | tools/virtio/ringtest/virtio_ring_0_9.c | 316 | ||||
| -rw-r--r-- | tools/virtio/ringtest/virtio_ring_poll.c | 2 |
13 files changed, 1148 insertions, 10 deletions
diff --git a/arch/sh/include/asm/barrier.h b/arch/sh/include/asm/barrier.h index f887c6465a82..8a84e05adb2e 100644 --- a/arch/sh/include/asm/barrier.h +++ b/arch/sh/include/asm/barrier.h @@ -33,7 +33,6 @@ #endif #define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0) -#define smp_store_mb(var, value) __smp_store_mb(var, value) #include <asm-generic/barrier.h> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c index 36205c27c4d0..f6bed86c17f9 100644 --- a/drivers/virtio/virtio_pci_common.c +++ b/drivers/virtio/virtio_pci_common.c @@ -545,6 +545,7 @@ err_enable_device: static void virtio_pci_remove(struct pci_dev *pci_dev) { struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev); + struct device *dev = get_device(&vp_dev->vdev.dev); unregister_virtio_device(&vp_dev->vdev); @@ -554,6 +555,7 @@ static void virtio_pci_remove(struct pci_dev *pci_dev) virtio_pci_modern_remove(vp_dev); pci_disable_device(pci_dev); + put_device(dev); } static struct pci_driver virtio_pci_driver = { diff --git a/tools/virtio/asm/barrier.h b/tools/virtio/asm/barrier.h index 26b7926bda88..ba34f9e96efd 100644 --- a/tools/virtio/asm/barrier.h +++ b/tools/virtio/asm/barrier.h @@ -1,15 +1,19 @@ #if defined(__i386__) || defined(__x86_64__) #define barrier() asm volatile("" ::: "memory") -#define mb() __sync_synchronize() - -#define smp_mb() mb() -# define dma_rmb() barrier() -# define dma_wmb() barrier() -# define smp_rmb() barrier() -# define smp_wmb() barrier() +#define virt_mb() __sync_synchronize() +#define virt_rmb() barrier() +#define virt_wmb() barrier() +/* Atomic store should be enough, but gcc generates worse code in that case. */ +#define virt_store_mb(var, value) do { \ + typeof(var) virt_store_mb_value = (value); \ + __atomic_exchange(&(var), &virt_store_mb_value, &virt_store_mb_value, \ + __ATOMIC_SEQ_CST); \ + barrier(); \ +} while (0); /* Weak barriers should be used. If not - it's a bug */ -# define rmb() abort() -# define wmb() abort() +# define mb() abort() +# define rmb() abort() +# define wmb() abort() #else #error Please fill in barrier macros #endif diff --git a/tools/virtio/linux/compiler.h b/tools/virtio/linux/compiler.h new file mode 100644 index 000000000000..845960e1cbf2 --- /dev/null +++ b/tools/virtio/linux/compiler.h @@ -0,0 +1,9 @@ +#ifndef LINUX_COMPILER_H +#define LINUX_COMPILER_H + +#define WRITE_ONCE(var, val) \ + (*((volatile typeof(val) *)(&(var))) = (val)) + +#define READ_ONCE(var) (*((volatile typeof(val) *)(&(var)))) + +#endif diff --git a/tools/virtio/linux/kernel.h b/tools/virtio/linux/kernel.h index 4db7d5691ba7..033849948215 100644 --- a/tools/virtio/linux/kernel.h +++ b/tools/virtio/linux/kernel.h @@ -8,6 +8,7 @@ #include <assert.h> #include <stdarg.h> +#include <linux/compiler.h> #include <linux/types.h> #include <linux/printk.h> #include <linux/bug.h> diff --git a/tools/virtio/ringtest/Makefile b/tools/virtio/ringtest/Makefile new file mode 100644 index 000000000000..feaa64ac4630 --- /dev/null +++ b/tools/virtio/ringtest/Makefile @@ -0,0 +1,22 @@ +all: + +all: ring virtio_ring_0_9 virtio_ring_poll + +CFLAGS += -Wall +CFLAGS += -pthread -O2 -ggdb +LDFLAGS += -pthread -O2 -ggdb + +main.o: main.c main.h +ring.o: ring.c main.h +virtio_ring_0_9.o: virtio_ring_0_9.c main.h +virtio_ring_poll.o: virtio_ring_poll.c virtio_ring_0_9.c main.h +ring: ring.o main.o +virtio_ring_0_9: virtio_ring_0_9.o main.o +virtio_ring_poll: virtio_ring_poll.o main.o +clean: + -rm main.o + -rm ring.o ring + -rm virtio_ring_0_9.o virtio_ring_0_9 + -rm virtio_ring_poll.o virtio_ring_poll + +.PHONY: all clean diff --git a/tools/virtio/ringtest/README b/tools/virtio/ringtest/README new file mode 100644 index 000000000000..34e94c46104f --- /dev/null +++ b/tools/virtio/ringtest/README @@ -0,0 +1,2 @@ +Partial implementation of various ring layouts, useful to tune virtio design. +Uses shared memory heavily. diff --git a/tools/virtio/ringtest/main.c b/tools/virtio/ringtest/main.c new file mode 100644 index 000000000000..3a5ff438bd62 --- /dev/null +++ b/tools/virtio/ringtest/main.c @@ -0,0 +1,366 @@ +/* + * Copyright (C) 2016 Red Hat, Inc. + * Author: Michael S. Tsirkin <mst@redhat.com> + * This work is licensed under the terms of the GNU GPL, version 2. + * + * Command line processing and common functions for ring benchmarking. + */ +#define _GNU_SOURCE +#include <getopt.h> +#include <pthread.h> +#include <assert.h> +#include <sched.h> +#include "main.h" +#include <sys/eventfd.h> +#include <stdlib.h> +#include <stdio.h> +#include <unistd.h> +#include <limits.h> + +int runcycles = 10000000; +int max_outstanding = INT_MAX; +int batch = 1; + +bool do_sleep = false; +bool do_relax = false; +bool do_exit = true; + +unsigned ring_size = 256; + +static int kickfd = -1; +static int callfd = -1; + +void notify(int fd) +{ + unsigned long long v = 1; + int r; + + vmexit(); + r = write(fd, &v, sizeof v); + assert(r == sizeof v); + vmentry(); +} + +void wait_for_notify(int fd) +{ + unsigned long long v = 1; + int r; + + vmexit(); + r = read(fd, &v, sizeof v); + assert(r == sizeof v); + vmentry(); +} + +void kick(void) +{ + notify(kickfd); +} + +void wait_for_kick(void) +{ + wait_for_notify(kickfd); +} + +void call(void) +{ + notify(callfd); +} + +void wait_for_call(void) +{ + wait_for_notify(callfd); +} + +void set_affinity(const char *arg) +{ + cpu_set_t cpuset; + int ret; + pthread_t self; + long int cpu; + char *endptr; + + if (!arg) + return; + + cpu = strtol(arg, &endptr, 0); + assert(!*endptr); + + assert(cpu >= 0 || cpu < CPU_SETSIZE); + + self = pthread_self(); + CPU_ZERO(&cpuset); + CPU_SET(cpu, &cpuset); + + ret = pthread_setaffinity_np(self, sizeof(cpu_set_t), &cpuset); + assert(!ret); +} + +static void run_guest(void) +{ + int completed_before; + int completed = 0; + int started = 0; + int bufs = runcycles; + int spurious = 0; + int r; + unsigned len; + void *buf; + int tokick = batch; + + for (;;) { + if (do_sleep) + disable_call(); + completed_before = completed; + do { + if (started < bufs && + started - completed < max_outstanding) { + r = add_inbuf(0, NULL, "Hello, world!"); + if (__builtin_expect(r == 0, true)) { + ++started; + if (!--tokick) { + tokick = batch; + if (do_sleep) + kick_available(); + } + + } + } else + r = -1; + + /* Flush out completed bufs if any */ + if (get_buf(&len, &buf)) { + ++completed; + if (__builtin_expect(completed == bufs, false)) + return; + r = 0; + } + } while (r == 0); + if (completed == completed_before) + ++spurious; + assert(completed <= bufs); + assert(started <= bufs); + if (do_sleep) { + if (enable_call()) + wait_for_call(); + } else { + poll_used(); + } + } +} + +static void run_host(void) +{ + int completed_before; + int completed = 0; + int spurious = 0; + int bufs = runcycles; + unsigned len; + void *buf; + + for (;;) { + if (do_sleep) { + if (enable_kick()) + wait_for_kick(); + } else { + poll_avail(); + } + if (do_sleep) + disable_kick(); + completed_before = completed; + while (__builtin_expect(use_buf(&len, &buf), true)) { + if (do_sleep) + call_used(); + ++completed; + if (__builtin_expect(completed == bufs, false)) + return; + } + if (completed == completed_before) + ++spurious; + assert(completed <= bufs); + if (completed == bufs) + break; + } +} + +void *start_guest(void *arg) +{ + set_affinity(arg); + run_guest(); + pthread_exit(NULL); +} + +void *start_host(void *arg) +{ + set_affinity(arg); + run_host(); + pthread_exit(NULL); +} + +static const char optstring[] = ""; +static const struct option longopts[] = { + { + .name = "help", + .has_arg = no_argument, + .val = 'h', + }, + { + .name = "host-affinity", + .has_arg = required_argument, + .val = 'H', + }, + { + .name = "guest-affinity", + .has_arg = required_argument, + .val = 'G', + }, + { + .name = "ring-size", + .has_arg = required_argument, + .val = 'R', + }, + { + .name = "run-cycles", + .has_arg = required_argument, + .val = 'C', + }, + { + .name = "outstanding", + .has_arg = required_argument, + .val = 'o', + }, + { + .name = "batch", + .has_arg = required_argument, + .val = 'b', + }, + { + .name = "sleep", + .has_arg = no_argument, + .val = 's', + }, + { + .name = "relax", + .has_arg = no_argument, + .val = 'x', + }, + { + .name = "exit", + .has_arg = no_argument, + .val = 'e', + }, + { + } +}; + +static void help(void) +{ + fprintf(stderr, "Usage: <test> [--help]" + " [--host-affinity H]" + " [--guest-affinity G]" + " [--ring-size R (default: %d)]" + " [--run-cycles C (default: %d)]" + " [--batch b]" + " [--outstanding o]" + " [--sleep]" + " [--relax]" + " [--exit]" + "\n", + ring_size, + runcycles); +} + +int main(int argc, char **argv) +{ + int ret; + pthread_t host, guest; + void *tret; + char *host_arg = NULL; + char *guest_arg = NULL; + char *endptr; + long int c; + + kickfd = eventfd(0, 0); + assert(kickfd >= 0); + callfd = eventfd(0, 0); + assert(callfd >= 0); + + for (;;) { + int o = getopt_long(argc, argv, optstring, longopts, NULL); + switch (o) { + case -1: + goto done; + case '?': + help(); + exit(2); + case 'H': + host_arg = optarg; + break; + case 'G': + guest_arg = optarg; + break; + case 'R': + ring_size = strtol(optarg, &endptr, 0); + assert(ring_size && !(ring_size & (ring_size - 1))); + assert(!*endptr); + break; + case 'C': + c = strtol(optarg, &endptr, 0); + assert(!*endptr); + assert(c > 0 && c < INT_MAX); + runcycles = c; + break; + case 'o': + c = strtol(optarg, &endptr, 0); + assert(!*endptr); + assert(c > 0 && c < INT_MAX); + max_outstanding = c; + break; + case 'b': + c = strtol(optarg, &endptr, 0); + assert(!*endptr); + assert(c > 0 && c < INT_MAX); + batch = c; + break; + case 's': + do_sleep = true; + break; + case 'x': + do_relax = true; + break; + case 'e': + do_exit = true; + break; + default: + help(); + exit(4); + break; + } + } + + /* does nothing here, used to make sure all smp APIs compile */ + smp_acquire(); + smp_release(); + smp_mb(); +done: + + if (batch > max_outstanding) + batch = max_outstanding; + + if (optind < argc) { + help(); + exit(4); + } + alloc_ring(); + + ret = pthread_create(&host, NULL, start_host, host_arg); + assert(!ret); + ret = pthread_create(&guest, NULL, start_guest, guest_arg); + assert(!ret); + + ret = pthread_join(guest, &tret); + assert(!ret); + ret = pthread_join(host, &tret); + assert(!ret); + return 0; +} diff --git a/tools/virtio/ringtest/main.h b/tools/virtio/ringtest/main.h new file mode 100644 index 000000000000..16917acb0ade --- /dev/null +++ b/tools/virtio/ringtest/main.h @@ -0,0 +1,119 @@ +/* + * Copyright (C) 2016 Red Hat, Inc. + * Author: Michael S. Tsirkin <mst@redhat.com> + * This work is licensed under the terms of the GNU GPL, version 2. + * + * Common macros and functions for ring benchmarking. + */ +#ifndef MAIN_H +#define MAIN_H + +#include <stdbool.h> + +extern bool do_exit; + +#if defined(__x86_64__) || defined(__i386__) +#include "x86intrin.h" + +static inline void wait_cycles(unsigned long long cycles) +{ + unsigned long long t; + + t = __rdtsc(); + while (__rdtsc() - t < cycles) {} +} + +#define VMEXIT_CYCLES 500 +#define VMENTRY_CYCLES 500 + +#else +static inline void wait_cycles(unsigned long long cycles) +{ + _Exit(5); +} +#define VMEXIT_CYCLES 0 +#define VMENTRY_CYCLES 0 +#endif + +static inline void vmexit(void) +{ + if (!do_exit) + return; + + wait_cycles(VMEXIT_CYCLES); +} +static inline void vmentry(void) +{ + if (!do_exit) + return; + + wait_cycles(VMENTRY_CYCLES); +} + +/* implemented by ring */ +void alloc_ring(void); +/* guest side */ +int add_inbuf(unsigned, void *, void *); +void *get_buf(unsigned *, void **); +void disable_call(); +bool enable_call(); +void kick_available(); +void poll_used(); +/* host side */ +void disable_kick(); +bool enable_kick(); +bool use_buf(unsigned *, void **); +void call_used(); +void poll_avail(); + +/* implemented by main */ +extern bool do_sleep; +void kick(void); +void wait_for_kick(void); +void call(void); +void wait_for_call(void); + +extern unsigned ring_size; + +/* Compiler barrier - similar to what Linux uses */ +#define barrier() asm volatile("" ::: "memory") + +/* Is there a portable way to do this? */ +#if defined(__x86_64__) || defined(__i386__) +#define cpu_relax() asm ("rep; nop" ::: "memory") +#else +#define cpu_relax() assert(0) +#endif + +extern bool do_relax; + +static inline void busy_wait(void) +{ + if (do_relax) + cpu_relax(); + else + /* prevent compiler from removing busy loops */ + barrier(); +} + +/* + * Not using __ATOMIC_SEQ_CST since gcc docs say they are only synchronized + * with other __ATOMIC_SEQ_CST calls. + */ +#define smp_mb() __sync_synchronize() + +/* + * This abuses the atomic builtins for thread fences, and + * adds a compiler barrier. + */ +#define smp_release() do { \ + barrier(); \ + __atomic_thread_fence(__ATOMIC_RELEASE); \ +} while (0) + +#define smp_acquire() do { \ + __atomic_thread_fence(__ATOMIC_ACQUIRE); \ + barrier(); \ +} while (0) + +#endif diff --git a/tools/virtio/ringtest/ring.c b/tools/virtio/ringtest/ring.c new file mode 100644 index 000000000000..c25c8d248b6b --- /dev/null +++ b/tools/virtio/ringtest/ring.c @@ -0,0 +1,272 @@ +/* + * Copyright (C) 2016 Red Hat, Inc. + * Author: Michael S. Tsirkin <mst@redhat.com> + * This work is licensed under the terms of the GNU GPL, version 2. + * + * Simple descriptor-based ring. virtio 0.9 compatible event index is used for + * signalling, unconditionally. + */ +#define _GNU_SOURCE +#include "main.h" +#include <stdlib.h> +#include <stdio.h> +#include <string.h> + +/* Next - Where next entry will be written. + * Prev - "Next" value when event triggered previously. + * Event - Peer requested event after writing this entry. + */ +static inline bool need_event(unsigned short event, + unsigned short next, + unsigned short prev) +{ + return (unsigned short)(next - event - 1) < (unsigned short)(next - prev); +} + +/* Design: + * Guest adds descriptors with unique index values and DESC_HW in flags. + * Host overwrites used descriptors with correct len, index, and DESC_HW clear. + * Flags are always set last. + */ +#define DESC_HW 0x1 + +struct desc { + unsigned short flags; + unsigned short index; + unsigned len; + unsigned long long addr; +}; + +/* how much padding is needed to avoid false cache sharing */ +#define HOST_GUEST_PADDING 0x80 + +/* Mostly read */ +struct event { + unsigned short kick_index; + unsigned char reserved0[HOST_GUEST_PADDING - 2]; + unsigned short call_index; + unsigned char reserved1[HOST_GUEST_PADDING - 2]; +}; + +struct data { + void *buf; /* descriptor is writeable, we can't get buf from there */ + void *data; +} *data; + +struct desc *ring; +struct event *event; + +struct guest { + unsigned avail_idx; + unsigned last_used_idx; + unsigned num_free; + unsigned kicked_avail_idx; + unsigned char reserved[HOST_GUEST_PADDING - 12]; +} guest; + +struct host { + /* we do not need to track last avail index + * unless we have more than one in flight. + */ + unsigned used_idx; + unsigned called_used_idx; + unsigned char reserved[HOST_GUEST_PADDING - 4]; +} host; + +/* implemented by ring */ +void alloc_ring(void) +{ + int ret; + int i; + + ret = posix_memalign((void **)&ring, 0x1000, ring_size * sizeof *ring); + if (ret) { + perror("Unable to allocate ring buffer.\n"); + exit(3); + } + event = malloc(sizeof *event); + if (!event) { + perror("Unable to allocate event buffer.\n"); + exit(3); + } + memset(event, 0, sizeof *event); + guest.avail_idx = 0; + guest.kicked_avail_idx = -1; + guest.last_used_idx = 0; + host.used_idx = 0; + host.called_used_idx = -1; + for (i = 0; i < ring_size; ++i) { + struct desc desc = { + .index = i, + }; + ring[i] = desc; + } + guest.num_free = ring_size; + data = malloc(ring_size * sizeof *data); + if (!data) { + perror("Unable to allocate data buffer.\n"); + exit(3); + } + memset(data, 0, ring_size * sizeof *data); +} + +/* guest side */ +int add_inbuf(unsigned len, void *buf, void *datap) +{ + unsigned head, index; + + if (!guest.num_free) + return -1; + + guest.num_free--; + head = (ring_size - 1) & (guest.avail_idx++); + + /* Start with a write. On MESI architectures this helps + * avoid a shared state with consumer that is polling this descriptor. + */ + ring[head].addr = (unsigned long)(void*)buf; + ring[head].len = len; + /* read below might bypass write above. That is OK because it's just an + * optimization. If this happens, we will get the cache line in a + * shared state which is unfortunate, but probably not worth it to + * add an explicit full barrier to avoid this. + */ + barrier(); + index = ring[head].index; + data[index].buf = buf; + data[index].data = datap; + /* Barrier A (for pairing) */ + smp_release(); + ring[head].flags = DESC_HW; + + return 0; +} + +void *get_buf(unsigned *lenp, void **bufp) +{ + unsigned head = (ring_size - 1) & guest.last_used_idx; + unsigned index; + void *datap; + + if (ring[head].flags & DESC_HW) + return NULL; + /* Barrier B (for pairing) */ + smp_acquire(); + *lenp = ring[head].len; + index = ring[head].index & (ring_size - 1); + datap = data[index].data; + *bufp = data[index].buf; + data[index].buf = NULL; + data[index].data = NULL; + guest.num_free++; + guest.last_used_idx++; + return datap; +} + +void poll_used(void) +{ + unsigned head = (ring_size - 1) & guest.last_used_idx; + + while (ring[head].flags & DESC_HW) + busy_wait(); +} + +void disable_call() +{ + /* Doing nothing to disable calls might cause + * extra interrupts, but reduces the number of cache misses. + */ +} + +bool enable_call() +{ + unsigned head = (ring_size - 1) & guest.last_used_idx; + + event->call_index = guest.last_used_idx; + /* Flush call index write */ + /* Barrier D (for pairing) */ + smp_mb(); + return ring[head].flags & DESC_HW; +} + +void kick_available(void) +{ + /* Flush in previous flags write */ + /* Barrier C (for pairing) */ + smp_mb(); + if (!need_event(event->kick_index, + guest.avail_idx, + guest.kicked_avail_idx)) + return; + + guest.kicked_avail_idx = guest.avail_idx; + kick(); +} + +/* host side */ +void disable_kick() +{ + /* Doing nothing to disable kicks might cause + * extra interrupts, but reduces the number of cache misses. + */ +} + +bool enable_kick() +{ + unsigned head = (ring_size - 1) & host.used_idx; + + event->kick_index = host.used_idx; + /* Barrier C (for pairing) */ + smp_mb(); + return !(ring[head].flags & DESC_HW); +} + +void poll_avail(void) +{ + unsigned head = (ring_size - 1) & host.used_idx; + + while (!(ring[head].flags & DESC_HW)) + busy_wait(); +} + +bool use_buf(unsigned *lenp, void **bufp) +{ + unsigned head = (ring_size - 1) & host.used_idx; + + if (!(ring[head].flags & DESC_HW)) + return false; + + /* make sure length read below is not speculated */ + /* Barrier A (for pairing) */ + smp_acquire(); + + /* simple in-order completion: we don't need + * to touch index at all. This also means we + * can just modify the descriptor in-place. + */ + ring[head].len--; + /* Make sure len is valid before flags. + * Note: alternative is to write len and flags in one access - + * possible on 64 bit architectures but wmb is free on Intel anyway + * so I have no way to test whether it's a gain. + */ + /* Barrier B (for pairing) */ + smp_release(); + ring[head].flags = 0; + host.used_idx++; + return true; +} + +void call_used(void) +{ + /* Flush in previous flags write */ + /* Barrier D (for pairing) */ + smp_mb(); + if (!need_event(event->call_index, + host.used_idx, + host.called_used_idx)) + return; + + host.called_used_idx = host.used_idx; + call(); +} diff --git a/tools/virtio/ringtest/run-on-all.sh b/tools/virtio/ringtest/run-on-all.sh new file mode 100755 index 000000000000..52b0f71ffa8d --- /dev/null +++ b/tools/virtio/ringtest/run-on-all.sh @@ -0,0 +1,24 @@ +#!/bin/sh + +#use last CPU for host. Why not the first? +#many devices tend to use cpu0 by default so +#it tends to be busier +HOST_AFFINITY=$(cd /dev/cpu; ls|grep -v '[a-z]'|sort -n|tail -1) + +#run command on all cpus +for cpu in $(cd /dev/cpu; ls|grep -v '[a-z]'|sort -n); +do + #Don't run guest and host on same CPU + #It actually works ok if using signalling + if + (echo "$@" | grep -e "--sleep" > /dev/null) || \ + test $HOST_AFFINITY '!=' $cpu + then + echo "GUEST AFFINITY $cpu" + "$@" --host-affinity $HOST_AFFINITY --guest-affinity $cpu + fi +done +echo "NO GUEST AFFINITY" +"$@" --host-affinity $HOST_AFFINITY +echo "NO AFFINITY" +"$@" diff --git a/tools/virtio/ringtest/virtio_ring_0_9.c b/tools/virtio/ringtest/virtio_ring_0_9.c new file mode 100644 index 000000000000..47c9a1a18d36 --- /dev/null +++ b/tools/virtio/ringtest/virtio_ring_0_9.c @@ -0,0 +1,316 @@ +/* + * Copyright (C) 2016 Red Hat, Inc. + * Author: Michael S. Tsirkin <mst@redhat.com> + * This work is licensed under the terms of the GNU GPL, version 2. + * + * Partial implementation of virtio 0.9. event index is used for signalling, + * unconditionally. Design roughly follows linux kernel implementation in order + * to be able to judge its performance. + */ +#define _GNU_SOURCE +#include "main.h" +#include <stdlib.h> +#include <stdio.h> +#include <assert.h> +#include <string.h> +#include <linux/virtio_ring.h> + +struct data { + void *data; +} *data; + +struct vring ring; + +/* enabling the below activates experimental ring polling code + * (which skips index reads on consumer in favor of looking at + * high bits of ring id ^ 0x8000). + */ +/* #ifdef RING_POLL */ + +/* how much padding is needed to avoid false cache sharing */ +#define HOST_GUEST_PADDING 0x80 + +struct guest { + unsigned short avail_idx; + unsigned short last_used_idx; + unsigned short num_free; + unsigned short kicked_avail_idx; + unsigned short free_head; + unsigned char reserved[HOST_GUEST_PADDING - 10]; +} guest; + +struct host { + /* we do not need to track last avail index + * unless we have more than one in flight. + */ + unsigned short used_idx; + unsigned short called_used_idx; + unsigned char reserved[HOST_GUEST_PADDING - 4]; +} host; + +/* implemented by ring */ +void alloc_ring(void) +{ + int ret; + int i; + void *p; + + ret = posix_memalign(&p, 0x1000, vring_size(ring_size, 0x1000)); + if (ret) { + perror("Unable to allocate ring buffer.\n"); + exit(3); + } + memset(p, 0, vring_size(ring_size, 0x1000)); + vring_init(&ring, ring_size, p, 0x1000); + + guest.avail_idx = 0; + guest.kicked_avail_idx = -1; + guest.last_used_idx = 0; + /* Put everything in free lists. */ + guest.free_head = 0; + for (i = 0; i < ring_size - 1; i++) + ring.desc[i].next = i + 1; + host.used_idx = 0; + host.called_used_idx = -1; + guest.num_free = ring_size; + data = malloc(ring_size * sizeof *data); + if (!data) { + perror("Unable to allocate data buffer.\n"); + exit(3); + } + memset(data, 0, ring_size * sizeof *data); +} + +/* guest side */ +int add_inbuf(unsigned len, void *buf, void *datap) +{ + unsigned head, avail; + struct vring_desc *desc; + + if (!guest.num_free) + return -1; + + head = guest.free_head; + guest.num_free--; + + desc = ring.desc; + desc[head].flags = VRING_DESC_F_NEXT; + desc[head].addr = (unsigned long)(void *)buf; + desc[head].len = len; + /* We do it like this to simulate the way + * we'd have to flip it if we had multiple + * descriptors. + */ + desc[head].flags &= ~VRING_DESC_F_NEXT; + guest.free_head = desc[head].next; + + data[head].data = datap; + +#ifdef RING_POLL + /* Barrier A (for pairing) */ + smp_release(); + avail = guest.avail_idx++; + ring.avail->ring[avail & (ring_size - 1)] = + (head | (avail & ~(ring_size - 1))) ^ 0x8000; +#else + avail = (ring_size - 1) & (guest.avail_idx++); + ring.avail->ring[avail] = head; + /* Barrier A (for pairing) */ + smp_release(); +#endif + ring.avail->idx = guest.avail_idx; + return 0; +} + +void *get_buf(unsigned *lenp, void **bufp) +{ + unsigned head; + unsigned index; + void *datap; + +#ifdef RING_POLL + head = (ring_size - 1) & guest.last_used_idx; + index = ring.used->ring[head].id; + if ((index ^ guest.last_used_idx ^ 0x8000) & ~(ring_size - 1)) + return NULL; + /* Barrier B (for pairing) */ + smp_acquire(); + index &= ring_size - 1; +#else + if (ring.used->idx == guest.last_used_idx) + return NULL; + /* Barrier B (for pairing) */ + smp_acquire(); + head = (ring_size - 1) & guest.last_used_idx; + index = ring.used->ring[head].id; +#endif + *lenp = ring.used->ring[head].len; + datap = data[index].data; + *bufp = (void*)(unsigned long)ring.desc[index].addr; + data[index].data = NULL; + ring.desc[index].next = guest.free_head; + guest.free_head = index; + guest.num_free++; + guest.last_used_idx++; + return datap; +} + +void poll_used(void) +{ +#ifdef RING_POLL + unsigned head = (ring_size - 1) & guest.last_used_idx; + + for (;;) { + unsigned index = ring.used->ring[head].id; + + if ((index ^ guest.last_used_idx ^ 0x8000) & ~(ring_size - 1)) + busy_wait(); + else + break; + } +#else + unsigned head = guest.last_used_idx; + + while (ring.used->idx == head) + busy_wait(); +#endif +} + +void disable_call() +{ + /* Doing nothing to disable calls might cause + * extra interrupts, but reduces the number of cache misses. + */ +} + +bool enable_call() +{ + unsigned short last_used_idx; + + vring_used_event(&ring) = (last_used_idx = guest.last_used_idx); + /* Flush call index write */ + /* Barrier D (for pairing) */ + smp_mb(); +#ifdef RING_POLL + { + unsigned short head = last_used_idx & (ring_size - 1); + unsigned index = ring.used->ring[head].id; + + return (index ^ last_used_idx ^ 0x8000) & ~(ring_size - 1); + } +#else + return ring.used->idx == last_used_idx; +#endif +} + +void kick_available(void) +{ + /* Flush in previous flags write */ + /* Barrier C (for pairing) */ + smp_mb(); + if (!vring_need_event(vring_avail_event(&ring), + guest.avail_idx, + guest.kicked_avail_idx)) + return; + + guest.kicked_avail_idx = guest.avail_idx; + kick(); +} + +/* host side */ +void disable_kick() +{ + /* Doing nothing to disable kicks might cause + * extra interrupts, but reduces the number of cache misses. + */ +} + +bool enable_kick() +{ + unsigned head = host.used_idx; + + vring_avail_event(&ring) = head; + /* Barrier C (for pairing) */ + smp_mb(); +#ifdef RING_POLL + { + unsigned index = ring.avail->ring[head & (ring_size - 1)]; + + return (index ^ head ^ 0x8000) & ~(ring_size - 1); + } +#else + return head == ring.avail->idx; +#endif +} + +void poll_avail(void) +{ + unsigned head = host.used_idx; +#ifdef RING_POLL + for (;;) { + unsigned index = ring.avail->ring[head & (ring_size - 1)]; + if ((index ^ head ^ 0x8000) & ~(ring_size - 1)) + busy_wait(); + else + break; + } +#else + while (ring.avail->idx == head) + busy_wait(); +#endif +} + +bool use_buf(unsigned *lenp, void **bufp) +{ + unsigned used_idx = host.used_idx; + struct vring_desc *desc; + unsigned head; + +#ifdef RING_POLL + head = ring.avail->ring[used_idx & (ring_size - 1)]; + if ((used_idx ^ head ^ 0x8000) & ~(ring_size - 1)) + return false; + /* Barrier A (for pairing) */ + smp_acquire(); + + used_idx &= ring_size - 1; + desc = &ring.desc[head & (ring_size - 1)]; +#else + if (used_idx == ring.avail->idx) + return false; + + /* Barrier A (for pairing) */ + smp_acquire(); + + used_idx &= ring_size - 1; + head = ring.avail->ring[used_idx]; + desc = &ring.desc[head]; +#endif + + *lenp = desc->len; + *bufp = (void *)(unsigned long)desc->addr; + + /* now update used ring */ + ring.used->ring[used_idx].id = head; + ring.used->ring[used_idx].len = desc->len - 1; + /* Barrier B (for pairing) */ + smp_release(); + host.used_idx++; + ring.used->idx = host.used_idx; + + return true; +} + +void call_used(void) +{ + /* Flush in previous flags write */ + /* Barrier D (for pairing) */ + smp_mb(); + if (!vring_need_event(vring_used_event(&ring), + host.used_idx, + host.called_used_idx)) + return; + + host.called_used_idx = host.used_idx; + call(); +} diff --git a/tools/virtio/ringtest/virtio_ring_poll.c b/tools/virtio/ringtest/virtio_ring_poll.c new file mode 100644 index 000000000000..84fc2c557aaa --- /dev/null +++ b/tools/virtio/ringtest/virtio_ring_poll.c @@ -0,0 +1,2 @@ +#define RING_POLL 1 +#include "virtio_ring_0_9.c" |