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 <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Eduardo Habkost <ehabkost@redhat.com> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
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@ -23,8 +23,8 @@ This function queries the presence of KVM cpuid leafs.
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function: define KVM_CPUID_FEATURES (0x40000001)
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returns : ebx, ecx, edx = 0
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eax = and OR'ed group of (1 << flag), where each flags is:
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returns : ebx, ecx
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eax = an OR'ed group of (1 << flag), where each flags is:
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flag || value || meaning
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@ -66,3 +66,14 @@ KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side
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|| || per-cpu warps are expected in
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|| || kvmclock.
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------------------------------------------------------------------------------
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edx = an OR'ed group of (1 << flag), where each flags is:
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flag || value || meaning
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==================================================================================
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KVM_HINTS_DEDICATED || 0 || guest checks this feature bit to
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|| || determine if there is vCPU pinning
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|| || and there is no vCPU over-commitment,
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|| || allowing optimizations
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----------------------------------------------------------------------------------
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@ -94,6 +94,11 @@ static inline unsigned int kvm_arch_para_features(void)
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return 0;
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}
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static inline unsigned int kvm_arch_para_hints(void)
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{
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return 0;
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}
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#ifdef CONFIG_MIPS_PARAVIRT
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static inline bool kvm_para_available(void)
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{
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@ -61,6 +61,11 @@ static inline unsigned int kvm_arch_para_features(void)
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return r;
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}
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static inline unsigned int kvm_arch_para_hints(void)
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{
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return 0;
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}
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static inline bool kvm_check_and_clear_guest_paused(void)
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{
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return false;
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@ -193,6 +193,11 @@ static inline unsigned int kvm_arch_para_features(void)
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return 0;
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}
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static inline unsigned int kvm_arch_para_hints(void)
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{
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return 0;
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}
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static inline bool kvm_check_and_clear_guest_paused(void)
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{
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return false;
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@ -88,6 +88,7 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned long p1,
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#ifdef CONFIG_KVM_GUEST
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bool kvm_para_available(void);
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unsigned int kvm_arch_para_features(void);
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unsigned int kvm_arch_para_hints(void);
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void kvm_async_pf_task_wait(u32 token, int interrupt_kernel);
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void kvm_async_pf_task_wake(u32 token);
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u32 kvm_read_and_reset_pf_reason(void);
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@ -115,6 +116,11 @@ static inline unsigned int kvm_arch_para_features(void)
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return 0;
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}
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static inline unsigned int kvm_arch_para_hints(void)
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{
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return 0;
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}
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static inline u32 kvm_read_and_reset_pf_reason(void)
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{
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return 0;
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@ -10,8 +10,10 @@
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*/
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#define KVM_CPUID_SIGNATURE 0x40000000
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/* This CPUID returns a feature bitmap in eax. Before enabling a particular
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* paravirtualization, the appropriate feature bit should be checked.
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/* This CPUID returns two feature bitmaps in eax, edx. Before enabling
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* a particular paravirtualization, the appropriate feature bit should
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* be checked in eax. The performance hint feature bit should be checked
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* in edx.
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*/
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#define KVM_CPUID_FEATURES 0x40000001
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#define KVM_FEATURE_CLOCKSOURCE 0
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@ -28,6 +30,8 @@
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#define KVM_FEATURE_PV_TLB_FLUSH 9
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#define KVM_FEATURE_ASYNC_PF_VMEXIT 10
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#define KVM_HINTS_DEDICATED 0
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/* The last 8 bits are used to indicate how to interpret the flags field
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* in pvclock structure. If no bits are set, all flags are ignored.
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*/
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@ -605,6 +605,11 @@ unsigned int kvm_arch_para_features(void)
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return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
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}
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unsigned int kvm_arch_para_hints(void)
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{
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return cpuid_edx(kvm_cpuid_base() | KVM_CPUID_FEATURES);
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}
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static uint32_t __init kvm_detect(void)
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{
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return kvm_cpuid_base();
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@ -19,6 +19,11 @@ static inline unsigned int kvm_arch_para_features(void)
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return 0;
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}
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static inline unsigned int kvm_arch_para_hints(void)
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{
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return 0;
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}
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static inline bool kvm_para_available(void)
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{
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return false;
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@ -9,4 +9,9 @@ static inline bool kvm_para_has_feature(unsigned int feature)
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{
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return !!(kvm_arch_para_features() & (1UL << feature));
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}
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static inline bool kvm_para_has_hint(unsigned int feature)
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{
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return !!(kvm_arch_para_hints() & (1UL << feature));
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}
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#endif /* __LINUX_KVM_PARA_H */
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