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authorMing Lei <ming.lei@canonical.com>2015-09-02 14:31:21 +0800
committerMarc Zyngier <marc.zyngier@arm.com>2015-09-17 13:13:27 +0100
commitef748917b529847277f07c98c55e1c0ce416449f (patch)
treef121d6fefff690152f4e8257c67ad7d807fa991b /arch/arm64
parent34c3faa353db8f5d3ce9966cf854d5643c64c4db (diff)
arm/arm64: KVM: Remove 'config KVM_ARM_MAX_VCPUS'
This patch removes config option of KVM_ARM_MAX_VCPUS, and like other ARCHs, just choose the maximum allowed value from hardware, and follows the reasons: 1) from distribution view, the option has to be defined as the max allowed value because it need to meet all kinds of virtulization applications and need to support most of SoCs; 2) using a bigger value doesn't introduce extra memory consumption, and the help text in Kconfig isn't accurate because kvm_vpu structure isn't allocated until request of creating VCPU is sent from QEMU; 3) the main effect is that the field of vcpus[] in 'struct kvm' becomes a bit bigger(sizeof(void *) per vcpu) and need more cache lines to hold the structure, but 'struct kvm' is one generic struct, and it has worked well on other ARCHs already in this way. Also, the world switch frequecy is often low, for example, it is ~2000 when running kernel building load in VM from APM xgene KVM host, so the effect is very small, and the difference can't be observed in my test at all. Cc: Dann Frazier <dann.frazier@canonical.com> Signed-off-by: Ming Lei <ming.lei@canonical.com> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/include/asm/kvm_host.h8
-rw-r--r--arch/arm64/kvm/Kconfig11
2 files changed, 2 insertions, 17 deletions
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 415938dc45cf..3fb58ea944eb 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -30,12 +30,6 @@
#define __KVM_HAVE_ARCH_INTC_INITIALIZED
-#if defined(CONFIG_KVM_ARM_MAX_VCPUS)
-#define KVM_MAX_VCPUS CONFIG_KVM_ARM_MAX_VCPUS
-#else
-#define KVM_MAX_VCPUS 0
-#endif
-
#define KVM_USER_MEM_SLOTS 32
#define KVM_PRIVATE_MEM_SLOTS 4
#define KVM_COALESCED_MMIO_PAGE_OFFSET 1
@@ -43,6 +37,8 @@
#include <kvm/arm_vgic.h>
#include <kvm/arm_arch_timer.h>
+#define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS
+
#define KVM_VCPU_MAX_FEATURES 3
int __attribute_const__ kvm_target_cpu(void);
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index bfffe8f4bd53..5c7e920e4861 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -41,15 +41,4 @@ config KVM_ARM_HOST
---help---
Provides host support for ARM processors.
-config KVM_ARM_MAX_VCPUS
- int "Number maximum supported virtual CPUs per VM"
- depends on KVM_ARM_HOST
- default 4
- help
- Static number of max supported virtual CPUs per VM.
-
- If you choose a high number, the vcpu structures will be quite
- large, so only choose a reasonable number that you expect to
- actually use.
-
endif # VIRTUALIZATION