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authorLinus Torvalds <torvalds@linux-foundation.org>2024-09-28 09:20:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2024-09-28 09:20:14 -0700
commit3efc57369a0ce8f76bf0804f7e673982384e4ac9 (patch)
tree13c88bd843f45b11fa923780e315127a828bf2b0 /virt
parente08d227840bb9366c6321ae1e480b37ba5eec29b (diff)
parentefbc6bd090f48ccf64f7a8dd5daea775821d57ec (diff)
Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull x86 kvm updates from Paolo Bonzini: "x86: - KVM currently invalidates the entirety of the page tables, not just those for the memslot being touched, when a memslot is moved or deleted. This does not traditionally have particularly noticeable overhead, but Intel's TDX will require the guest to re-accept private pages if they are dropped from the secure EPT, which is a non starter. Actually, the only reason why this is not already being done is a bug which was never fully investigated and caused VM instability with assigned GeForce GPUs, so allow userspace to opt into the new behavior. - Advertise AVX10.1 to userspace (effectively prep work for the "real" AVX10 functionality that is on the horizon) - Rework common MSR handling code to suppress errors on userspace accesses to unsupported-but-advertised MSRs This will allow removing (almost?) all of KVM's exemptions for userspace access to MSRs that shouldn't exist based on the vCPU model (the actual cleanup is non-trivial future work) - Rework KVM's handling of x2APIC ICR, again, because AMD (x2AVIC) splits the 64-bit value into the legacy ICR and ICR2 storage, whereas Intel (APICv) stores the entire 64-bit value at the ICR offset - Fix a bug where KVM would fail to exit to userspace if one was triggered by a fastpath exit handler - Add fastpath handling of HLT VM-Exit to expedite re-entering the guest when there's already a pending wake event at the time of the exit - Fix a WARN caused by RSM entering a nested guest from SMM with invalid guest state, by forcing the vCPU out of guest mode prior to signalling SHUTDOWN (the SHUTDOWN hits the VM altogether, not the nested guest) - Overhaul the "unprotect and retry" logic to more precisely identify cases where retrying is actually helpful, and to harden all retry paths against putting the guest into an infinite retry loop - Add support for yielding, e.g. to honor NEED_RESCHED, when zapping rmaps in the shadow MMU - Refactor pieces of the shadow MMU related to aging SPTEs in prepartion for adding multi generation LRU support in KVM - Don't stuff the RSB after VM-Exit when RETPOLINE=y and AutoIBRS is enabled, i.e. when the CPU has already flushed the RSB - Trace the per-CPU host save area as a VMCB pointer to improve readability and cleanup the retrieval of the SEV-ES host save area - Remove unnecessary accounting of temporary nested VMCB related allocations - Set FINAL/PAGE in the page fault error code for EPT violations if and only if the GVA is valid. If the GVA is NOT valid, there is no guest-side page table walk and so stuffing paging related metadata is nonsensical - Fix a bug where KVM would incorrectly synthesize a nested VM-Exit instead of emulating posted interrupt delivery to L2 - Add a lockdep assertion to detect unsafe accesses of vmcs12 structures - Harden eVMCS loading against an impossible NULL pointer deref (really truly should be impossible) - Minor SGX fix and a cleanup - Misc cleanups Generic: - Register KVM's cpuhp and syscore callbacks when enabling virtualization in hardware, as the sole purpose of said callbacks is to disable and re-enable virtualization as needed - Enable virtualization when KVM is loaded, not right before the first VM is created Together with the previous change, this simplifies a lot the logic of the callbacks, because their very existence implies virtualization is enabled - Fix a bug that results in KVM prematurely exiting to userspace for coalesced MMIO/PIO in many cases, clean up the related code, and add a testcase - Fix a bug in kvm_clear_guest() where it would trigger a buffer overflow _if_ the gpa+len crosses a page boundary, which thankfully is guaranteed to not happen in the current code base. Add WARNs in more helpers that read/write guest memory to detect similar bugs Selftests: - Fix a goof that caused some Hyper-V tests to be skipped when run on bare metal, i.e. NOT in a VM - Add a regression test for KVM's handling of SHUTDOWN for an SEV-ES guest - Explicitly include one-off assets in .gitignore. Past Sean was completely wrong about not being able to detect missing .gitignore entries - Verify userspace single-stepping works when KVM happens to handle a VM-Exit in its fastpath - Misc cleanups" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (127 commits) Documentation: KVM: fix warning in "make htmldocs" s390: Enable KVM_S390_UCONTROL config in debug_defconfig selftests: kvm: s390: Add VM run test case KVM: SVM: let alternatives handle the cases when RSB filling is required KVM: VMX: Set PFERR_GUEST_{FINAL,PAGE}_MASK if and only if the GVA is valid KVM: x86/mmu: Use KVM_PAGES_PER_HPAGE() instead of an open coded equivalent KVM: x86/mmu: Add KVM_RMAP_MANY to replace open coded '1' and '1ul' literals KVM: x86/mmu: Fold mmu_spte_age() into kvm_rmap_age_gfn_range() KVM: x86/mmu: Morph kvm_handle_gfn_range() into an aging specific helper KVM: x86/mmu: Honor NEED_RESCHED when zapping rmaps and blocking is allowed KVM: x86/mmu: Add a helper to walk and zap rmaps for a memslot KVM: x86/mmu: Plumb a @can_yield parameter into __walk_slot_rmaps() KVM: x86/mmu: Move walk_slot_rmaps() up near for_each_slot_rmap_range() KVM: x86/mmu: WARN on MMIO cache hit when emulating write-protected gfn KVM: x86/mmu: Detect if unprotect will do anything based on invalid_list KVM: x86/mmu: Subsume kvm_mmu_unprotect_page() into the and_retry() version KVM: x86: Rename reexecute_instruction()=>kvm_unprotect_and_retry_on_failure() KVM: x86: Update retry protection fields when forcing retry on emulation failure KVM: x86: Apply retry protection to "unprotect on failure" path KVM: x86: Check EMULTYPE_WRITE_PF_TO_SP before unprotecting gfn ...
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/coalesced_mmio.c31
-rw-r--r--virt/kvm/kvm_main.c281
2 files changed, 152 insertions, 160 deletions
diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index 1b90acb6e3fe..375d6285475e 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -40,27 +40,6 @@ static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
return 1;
}
-static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev, u32 last)
-{
- struct kvm_coalesced_mmio_ring *ring;
- unsigned avail;
-
- /* Are we able to batch it ? */
-
- /* last is the first free entry
- * check if we don't meet the first used entry
- * there is always one unused entry in the buffer
- */
- ring = dev->kvm->coalesced_mmio_ring;
- avail = (ring->first - last - 1) % KVM_COALESCED_MMIO_MAX;
- if (avail == 0) {
- /* full */
- return 0;
- }
-
- return 1;
-}
-
static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
struct kvm_io_device *this, gpa_t addr,
int len, const void *val)
@@ -74,9 +53,15 @@ static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
spin_lock(&dev->kvm->ring_lock);
+ /*
+ * last is the index of the entry to fill. Verify userspace hasn't
+ * set last to be out of range, and that there is room in the ring.
+ * Leave one entry free in the ring so that userspace can differentiate
+ * between an empty ring and a full ring.
+ */
insert = READ_ONCE(ring->last);
- if (!coalesced_mmio_has_room(dev, insert) ||
- insert >= KVM_COALESCED_MMIO_MAX) {
+ if (insert >= KVM_COALESCED_MMIO_MAX ||
+ (insert + 1) % KVM_COALESCED_MMIO_MAX == READ_ONCE(ring->first)) {
spin_unlock(&dev->kvm->ring_lock);
return -EOPNOTSUPP;
}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4f81366f8b61..05cbb2548d99 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -136,8 +136,8 @@ static int kvm_no_compat_open(struct inode *inode, struct file *file)
#define KVM_COMPAT(c) .compat_ioctl = kvm_no_compat_ioctl, \
.open = kvm_no_compat_open
#endif
-static int hardware_enable_all(void);
-static void hardware_disable_all(void);
+static int kvm_enable_virtualization(void);
+static void kvm_disable_virtualization(void);
static void kvm_io_bus_destroy(struct kvm_io_bus *bus);
@@ -1220,7 +1220,7 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
if (r)
goto out_err_no_arch_destroy_vm;
- r = hardware_enable_all();
+ r = kvm_enable_virtualization();
if (r)
goto out_err_no_disable;
@@ -1263,7 +1263,7 @@ out_no_coalesced_mmio:
mmu_notifier_unregister(&kvm->mmu_notifier, current->mm);
#endif
out_err_no_mmu_notifier:
- hardware_disable_all();
+ kvm_disable_virtualization();
out_err_no_disable:
kvm_arch_destroy_vm(kvm);
out_err_no_arch_destroy_vm:
@@ -1360,7 +1360,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
#endif
kvm_arch_free_vm(kvm);
preempt_notifier_dec();
- hardware_disable_all();
+ kvm_disable_virtualization();
mmdrop(mm);
}
@@ -3270,6 +3270,9 @@ static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn,
int r;
unsigned long addr;
+ if (WARN_ON_ONCE(offset + len > PAGE_SIZE))
+ return -EFAULT;
+
addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
if (kvm_is_error_hva(addr))
return -EFAULT;
@@ -3343,6 +3346,9 @@ static int __kvm_read_guest_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
int r;
unsigned long addr;
+ if (WARN_ON_ONCE(offset + len > PAGE_SIZE))
+ return -EFAULT;
+
addr = gfn_to_hva_memslot_prot(slot, gfn, NULL);
if (kvm_is_error_hva(addr))
return -EFAULT;
@@ -3373,6 +3379,9 @@ static int __kvm_write_guest_page(struct kvm *kvm,
int r;
unsigned long addr;
+ if (WARN_ON_ONCE(offset + len > PAGE_SIZE))
+ return -EFAULT;
+
addr = gfn_to_hva_memslot(memslot, gfn);
if (kvm_is_error_hva(addr))
return -EFAULT;
@@ -3576,7 +3585,7 @@ int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len)
int ret;
while ((seg = next_segment(len, offset)) != 0) {
- ret = kvm_write_guest_page(kvm, gfn, zero_page, offset, len);
+ ret = kvm_write_guest_page(kvm, gfn, zero_page, offset, seg);
if (ret < 0)
return ret;
offset = 0;
@@ -5566,137 +5575,67 @@ static struct miscdevice kvm_dev = {
};
#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
+static bool enable_virt_at_load = true;
+module_param(enable_virt_at_load, bool, 0444);
+
__visible bool kvm_rebooting;
EXPORT_SYMBOL_GPL(kvm_rebooting);
-static DEFINE_PER_CPU(bool, hardware_enabled);
+static DEFINE_PER_CPU(bool, virtualization_enabled);
+static DEFINE_MUTEX(kvm_usage_lock);
static int kvm_usage_count;
-static int __hardware_enable_nolock(void)
+__weak void kvm_arch_enable_virtualization(void)
+{
+
+}
+
+__weak void kvm_arch_disable_virtualization(void)
+{
+
+}
+
+static int kvm_enable_virtualization_cpu(void)
{
- if (__this_cpu_read(hardware_enabled))
+ if (__this_cpu_read(virtualization_enabled))
return 0;
- if (kvm_arch_hardware_enable()) {
+ if (kvm_arch_enable_virtualization_cpu()) {
pr_info("kvm: enabling virtualization on CPU%d failed\n",
raw_smp_processor_id());
return -EIO;
}
- __this_cpu_write(hardware_enabled, true);
+ __this_cpu_write(virtualization_enabled, true);
return 0;
}
-static void hardware_enable_nolock(void *failed)
-{
- if (__hardware_enable_nolock())
- atomic_inc(failed);
-}
-
static int kvm_online_cpu(unsigned int cpu)
{
- int ret = 0;
-
/*
* Abort the CPU online process if hardware virtualization cannot
* be enabled. Otherwise running VMs would encounter unrecoverable
* errors when scheduled to this CPU.
*/
- mutex_lock(&kvm_lock);
- if (kvm_usage_count)
- ret = __hardware_enable_nolock();
- mutex_unlock(&kvm_lock);
- return ret;
+ return kvm_enable_virtualization_cpu();
}
-static void hardware_disable_nolock(void *junk)
+static void kvm_disable_virtualization_cpu(void *ign)
{
- /*
- * Note, hardware_disable_all_nolock() tells all online CPUs to disable
- * hardware, not just CPUs that successfully enabled hardware!
- */
- if (!__this_cpu_read(hardware_enabled))
+ if (!__this_cpu_read(virtualization_enabled))
return;
- kvm_arch_hardware_disable();
+ kvm_arch_disable_virtualization_cpu();
- __this_cpu_write(hardware_enabled, false);
+ __this_cpu_write(virtualization_enabled, false);
}
static int kvm_offline_cpu(unsigned int cpu)
{
- mutex_lock(&kvm_lock);
- if (kvm_usage_count)
- hardware_disable_nolock(NULL);
- mutex_unlock(&kvm_lock);
+ kvm_disable_virtualization_cpu(NULL);
return 0;
}
-static void hardware_disable_all_nolock(void)
-{
- BUG_ON(!kvm_usage_count);
-
- kvm_usage_count--;
- if (!kvm_usage_count)
- on_each_cpu(hardware_disable_nolock, NULL, 1);
-}
-
-static void hardware_disable_all(void)
-{
- cpus_read_lock();
- mutex_lock(&kvm_lock);
- hardware_disable_all_nolock();
- mutex_unlock(&kvm_lock);
- cpus_read_unlock();
-}
-
-static int hardware_enable_all(void)
-{
- atomic_t failed = ATOMIC_INIT(0);
- int r;
-
- /*
- * Do not enable hardware virtualization if the system is going down.
- * If userspace initiated a forced reboot, e.g. reboot -f, then it's
- * possible for an in-flight KVM_CREATE_VM to trigger hardware enabling
- * after kvm_reboot() is called. Note, this relies on system_state
- * being set _before_ kvm_reboot(), which is why KVM uses a syscore ops
- * hook instead of registering a dedicated reboot notifier (the latter
- * runs before system_state is updated).
- */
- if (system_state == SYSTEM_HALT || system_state == SYSTEM_POWER_OFF ||
- system_state == SYSTEM_RESTART)
- return -EBUSY;
-
- /*
- * When onlining a CPU, cpu_online_mask is set before kvm_online_cpu()
- * is called, and so on_each_cpu() between them includes the CPU that
- * is being onlined. As a result, hardware_enable_nolock() may get
- * invoked before kvm_online_cpu(), which also enables hardware if the
- * usage count is non-zero. Disable CPU hotplug to avoid attempting to
- * enable hardware multiple times.
- */
- cpus_read_lock();
- mutex_lock(&kvm_lock);
-
- r = 0;
-
- kvm_usage_count++;
- if (kvm_usage_count == 1) {
- on_each_cpu(hardware_enable_nolock, &failed, 1);
-
- if (atomic_read(&failed)) {
- hardware_disable_all_nolock();
- r = -EBUSY;
- }
- }
-
- mutex_unlock(&kvm_lock);
- cpus_read_unlock();
-
- return r;
-}
-
static void kvm_shutdown(void)
{
/*
@@ -5712,34 +5651,32 @@ static void kvm_shutdown(void)
*/
pr_info("kvm: exiting hardware virtualization\n");
kvm_rebooting = true;
- on_each_cpu(hardware_disable_nolock, NULL, 1);
+ on_each_cpu(kvm_disable_virtualization_cpu, NULL, 1);
}
static int kvm_suspend(void)
{
/*
* Secondary CPUs and CPU hotplug are disabled across the suspend/resume
- * callbacks, i.e. no need to acquire kvm_lock to ensure the usage count
- * is stable. Assert that kvm_lock is not held to ensure the system
- * isn't suspended while KVM is enabling hardware. Hardware enabling
- * can be preempted, but the task cannot be frozen until it has dropped
- * all locks (userspace tasks are frozen via a fake signal).
+ * callbacks, i.e. no need to acquire kvm_usage_lock to ensure the usage
+ * count is stable. Assert that kvm_usage_lock is not held to ensure
+ * the system isn't suspended while KVM is enabling hardware. Hardware
+ * enabling can be preempted, but the task cannot be frozen until it has
+ * dropped all locks (userspace tasks are frozen via a fake signal).
*/
- lockdep_assert_not_held(&kvm_lock);
+ lockdep_assert_not_held(&kvm_usage_lock);
lockdep_assert_irqs_disabled();
- if (kvm_usage_count)
- hardware_disable_nolock(NULL);
+ kvm_disable_virtualization_cpu(NULL);
return 0;
}
static void kvm_resume(void)
{
- lockdep_assert_not_held(&kvm_lock);
+ lockdep_assert_not_held(&kvm_usage_lock);
lockdep_assert_irqs_disabled();
- if (kvm_usage_count)
- WARN_ON_ONCE(__hardware_enable_nolock());
+ WARN_ON_ONCE(kvm_enable_virtualization_cpu());
}
static struct syscore_ops kvm_syscore_ops = {
@@ -5747,13 +5684,95 @@ static struct syscore_ops kvm_syscore_ops = {
.resume = kvm_resume,
.shutdown = kvm_shutdown,
};
+
+static int kvm_enable_virtualization(void)
+{
+ int r;
+
+ guard(mutex)(&kvm_usage_lock);
+
+ if (kvm_usage_count++)
+ return 0;
+
+ kvm_arch_enable_virtualization();
+
+ r = cpuhp_setup_state(CPUHP_AP_KVM_ONLINE, "kvm/cpu:online",
+ kvm_online_cpu, kvm_offline_cpu);
+ if (r)
+ goto err_cpuhp;
+
+ register_syscore_ops(&kvm_syscore_ops);
+
+ /*
+ * Undo virtualization enabling and bail if the system is going down.
+ * If userspace initiated a forced reboot, e.g. reboot -f, then it's
+ * possible for an in-flight operation to enable virtualization after
+ * syscore_shutdown() is called, i.e. without kvm_shutdown() being
+ * invoked. Note, this relies on system_state being set _before_
+ * kvm_shutdown(), e.g. to ensure either kvm_shutdown() is invoked
+ * or this CPU observes the impending shutdown. Which is why KVM uses
+ * a syscore ops hook instead of registering a dedicated reboot
+ * notifier (the latter runs before system_state is updated).
+ */
+ if (system_state == SYSTEM_HALT || system_state == SYSTEM_POWER_OFF ||
+ system_state == SYSTEM_RESTART) {
+ r = -EBUSY;
+ goto err_rebooting;
+ }
+
+ return 0;
+
+err_rebooting:
+ unregister_syscore_ops(&kvm_syscore_ops);
+ cpuhp_remove_state(CPUHP_AP_KVM_ONLINE);
+err_cpuhp:
+ kvm_arch_disable_virtualization();
+ --kvm_usage_count;
+ return r;
+}
+
+static void kvm_disable_virtualization(void)
+{
+ guard(mutex)(&kvm_usage_lock);
+
+ if (--kvm_usage_count)
+ return;
+
+ unregister_syscore_ops(&kvm_syscore_ops);
+ cpuhp_remove_state(CPUHP_AP_KVM_ONLINE);
+ kvm_arch_disable_virtualization();
+}
+
+static int kvm_init_virtualization(void)
+{
+ if (enable_virt_at_load)
+ return kvm_enable_virtualization();
+
+ return 0;
+}
+
+static void kvm_uninit_virtualization(void)
+{
+ if (enable_virt_at_load)
+ kvm_disable_virtualization();
+}
#else /* CONFIG_KVM_GENERIC_HARDWARE_ENABLING */
-static int hardware_enable_all(void)
+static int kvm_enable_virtualization(void)
+{
+ return 0;
+}
+
+static int kvm_init_virtualization(void)
{
return 0;
}
-static void hardware_disable_all(void)
+static void kvm_disable_virtualization(void)
+{
+
+}
+
+static void kvm_uninit_virtualization(void)
{
}
@@ -6454,15 +6473,6 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
int r;
int cpu;
-#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
- r = cpuhp_setup_state_nocalls(CPUHP_AP_KVM_ONLINE, "kvm/cpu:online",
- kvm_online_cpu, kvm_offline_cpu);
- if (r)
- return r;
-
- register_syscore_ops(&kvm_syscore_ops);
-#endif
-
/* A kmem cache lets us meet the alignment requirements of fx_save. */
if (!vcpu_align)
vcpu_align = __alignof__(struct kvm_vcpu);
@@ -6473,10 +6483,8 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
offsetofend(struct kvm_vcpu, stats_id)
- offsetof(struct kvm_vcpu, arch),
NULL);
- if (!kvm_vcpu_cache) {
- r = -ENOMEM;
- goto err_vcpu_cache;
- }
+ if (!kvm_vcpu_cache)
+ return -ENOMEM;
for_each_possible_cpu(cpu) {
if (!alloc_cpumask_var_node(&per_cpu(cpu_kick_mask, cpu),
@@ -6510,6 +6518,10 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
kvm_gmem_init(module);
+ r = kvm_init_virtualization();
+ if (r)
+ goto err_virt;
+
/*
* Registration _must_ be the very last thing done, as this exposes
* /dev/kvm to userspace, i.e. all infrastructure must be setup!
@@ -6523,6 +6535,8 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
return 0;
err_register:
+ kvm_uninit_virtualization();
+err_virt:
kvm_vfio_ops_exit();
err_vfio:
kvm_async_pf_deinit();
@@ -6533,11 +6547,6 @@ err_cpu_kick_mask:
for_each_possible_cpu(cpu)
free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
kmem_cache_destroy(kvm_vcpu_cache);
-err_vcpu_cache:
-#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
- unregister_syscore_ops(&kvm_syscore_ops);
- cpuhp_remove_state_nocalls(CPUHP_AP_KVM_ONLINE);
-#endif
return r;
}
EXPORT_SYMBOL_GPL(kvm_init);
@@ -6553,16 +6562,14 @@ void kvm_exit(void)
*/
misc_deregister(&kvm_dev);
+ kvm_uninit_virtualization();
+
debugfs_remove_recursive(kvm_debugfs_dir);
for_each_possible_cpu(cpu)
free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
kmem_cache_destroy(kvm_vcpu_cache);
kvm_vfio_ops_exit();
kvm_async_pf_deinit();
-#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
- unregister_syscore_ops(&kvm_syscore_ops);
- cpuhp_remove_state_nocalls(CPUHP_AP_KVM_ONLINE);
-#endif
kvm_irqfd_exit();
}
EXPORT_SYMBOL_GPL(kvm_exit);