From: Wanpeng Li Date: Tue, 13 Feb 2018 01:05:40 +0000 (+0800) Subject: KVM: Introduce paravirtualization hints and KVM_HINTS_DEDICATED X-Git-Tag: v4.17-rc1~72^2~79 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a4429e53c9b3082b05e51224c3d58dbdd39306c5;p=thirdparty%2Flinux.git KVM: Introduce paravirtualization hints and KVM_HINTS_DEDICATED This patch introduces kvm_para_has_hint() to query for hints about the configuration of the guests. The first hint KVM_HINTS_DEDICATED, is set if the guest has dedicated physical CPUs for each vCPU (i.e. pinning and no over-commitment). This allows optimizing spinlocks and tells the guest to avoid PV TLB flush. Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Eduardo Habkost Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini Signed-off-by: Radim Krčmář --- diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt index 87a7506f31c2b..d4f33eb805dd2 100644 --- a/Documentation/virtual/kvm/cpuid.txt +++ b/Documentation/virtual/kvm/cpuid.txt @@ -23,8 +23,8 @@ This function queries the presence of KVM cpuid leafs. function: define KVM_CPUID_FEATURES (0x40000001) -returns : ebx, ecx, edx = 0 - eax = and OR'ed group of (1 << flag), where each flags is: +returns : ebx, ecx + eax = an OR'ed group of (1 << flag), where each flags is: flag || value || meaning @@ -66,3 +66,14 @@ KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side || || per-cpu warps are expected in || || kvmclock. ------------------------------------------------------------------------------ + + edx = an OR'ed group of (1 << flag), where each flags is: + + +flag || value || meaning +================================================================================== +KVM_HINTS_DEDICATED || 0 || guest checks this feature bit to + || || determine if there is vCPU pinning + || || and there is no vCPU over-commitment, + || || allowing optimizations +---------------------------------------------------------------------------------- diff --git a/arch/mips/include/asm/kvm_para.h b/arch/mips/include/asm/kvm_para.h index 60b1aa0b7014a..b57e978b0946e 100644 --- a/arch/mips/include/asm/kvm_para.h +++ b/arch/mips/include/asm/kvm_para.h @@ -94,6 +94,11 @@ static inline unsigned int kvm_arch_para_features(void) return 0; } +static inline unsigned int kvm_arch_para_hints(void) +{ + return 0; +} + #ifdef CONFIG_MIPS_PARAVIRT static inline bool kvm_para_available(void) { diff --git a/arch/powerpc/include/asm/kvm_para.h b/arch/powerpc/include/asm/kvm_para.h index 336a91acb8b1f..5ceb4efca65f9 100644 --- a/arch/powerpc/include/asm/kvm_para.h +++ b/arch/powerpc/include/asm/kvm_para.h @@ -61,6 +61,11 @@ static inline unsigned int kvm_arch_para_features(void) return r; } +static inline unsigned int kvm_arch_para_hints(void) +{ + return 0; +} + static inline bool kvm_check_and_clear_guest_paused(void) { return false; diff --git a/arch/s390/include/asm/kvm_para.h b/arch/s390/include/asm/kvm_para.h index 74eeec9c0a809..cbc7c3a68e4df 100644 --- a/arch/s390/include/asm/kvm_para.h +++ b/arch/s390/include/asm/kvm_para.h @@ -193,6 +193,11 @@ static inline unsigned int kvm_arch_para_features(void) return 0; } +static inline unsigned int kvm_arch_para_hints(void) +{ + return 0; +} + static inline bool kvm_check_and_clear_guest_paused(void) { return false; diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index 7b407dda2bd71..3aea2658323a5 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -88,6 +88,7 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned long p1, #ifdef CONFIG_KVM_GUEST bool kvm_para_available(void); unsigned int kvm_arch_para_features(void); +unsigned int kvm_arch_para_hints(void); void kvm_async_pf_task_wait(u32 token, int interrupt_kernel); void kvm_async_pf_task_wake(u32 token); u32 kvm_read_and_reset_pf_reason(void); @@ -115,6 +116,11 @@ static inline unsigned int kvm_arch_para_features(void) return 0; } +static inline unsigned int kvm_arch_para_hints(void) +{ + return 0; +} + static inline u32 kvm_read_and_reset_pf_reason(void) { return 0; diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h index 6cfa9c8cb7d65..68a41b6ba3da3 100644 --- a/arch/x86/include/uapi/asm/kvm_para.h +++ b/arch/x86/include/uapi/asm/kvm_para.h @@ -10,8 +10,10 @@ */ #define KVM_CPUID_SIGNATURE 0x40000000 -/* This CPUID returns a feature bitmap in eax. Before enabling a particular - * paravirtualization, the appropriate feature bit should be checked. +/* This CPUID returns two feature bitmaps in eax, edx. Before enabling + * a particular paravirtualization, the appropriate feature bit should + * be checked in eax. The performance hint feature bit should be checked + * in edx. */ #define KVM_CPUID_FEATURES 0x40000001 #define KVM_FEATURE_CLOCKSOURCE 0 @@ -28,6 +30,8 @@ #define KVM_FEATURE_PV_TLB_FLUSH 9 #define KVM_FEATURE_ASYNC_PF_VMEXIT 10 +#define KVM_HINTS_DEDICATED 0 + /* The last 8 bits are used to indicate how to interpret the flags field * in pvclock structure. If no bits are set, all flags are ignored. */ diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index bc1a27280c4bf..8c9d98c46f840 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -605,6 +605,11 @@ unsigned int kvm_arch_para_features(void) return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES); } +unsigned int kvm_arch_para_hints(void) +{ + return cpuid_edx(kvm_cpuid_base() | KVM_CPUID_FEATURES); +} + static uint32_t __init kvm_detect(void) { return kvm_cpuid_base(); diff --git a/include/asm-generic/kvm_para.h b/include/asm-generic/kvm_para.h index 18c6abe81fbdc..728e5c5706c4e 100644 --- a/include/asm-generic/kvm_para.h +++ b/include/asm-generic/kvm_para.h @@ -19,6 +19,11 @@ static inline unsigned int kvm_arch_para_features(void) return 0; } +static inline unsigned int kvm_arch_para_hints(void) +{ + return 0; +} + static inline bool kvm_para_available(void) { return false; diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h index 51f6ef2c2ff46..f23b90b02898a 100644 --- a/include/linux/kvm_para.h +++ b/include/linux/kvm_para.h @@ -9,4 +9,9 @@ static inline bool kvm_para_has_feature(unsigned int feature) { return !!(kvm_arch_para_features() & (1UL << feature)); } + +static inline bool kvm_para_has_hint(unsigned int feature) +{ + return !!(kvm_arch_para_hints() & (1UL << feature)); +} #endif /* __LINUX_KVM_PARA_H */