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>
This commit is contained in:
Wanpeng Li 2018-02-13 09:05:40 +08:00 committed by Radim Krčmář
parent d4c67a7a54
commit a4429e53c9
9 changed files with 55 additions and 4 deletions

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@ -23,8 +23,8 @@ This function queries the presence of KVM cpuid leafs.
function: define KVM_CPUID_FEATURES (0x40000001) function: define KVM_CPUID_FEATURES (0x40000001)
returns : ebx, ecx, edx = 0 returns : ebx, ecx
eax = and OR'ed group of (1 << flag), where each flags is: eax = an OR'ed group of (1 << flag), where each flags is:
flag || value || meaning 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 || || per-cpu warps are expected in
|| || kvmclock. || || 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
----------------------------------------------------------------------------------

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@ -94,6 +94,11 @@ static inline unsigned int kvm_arch_para_features(void)
return 0; return 0;
} }
static inline unsigned int kvm_arch_para_hints(void)
{
return 0;
}
#ifdef CONFIG_MIPS_PARAVIRT #ifdef CONFIG_MIPS_PARAVIRT
static inline bool kvm_para_available(void) static inline bool kvm_para_available(void)
{ {

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@ -61,6 +61,11 @@ static inline unsigned int kvm_arch_para_features(void)
return r; return r;
} }
static inline unsigned int kvm_arch_para_hints(void)
{
return 0;
}
static inline bool kvm_check_and_clear_guest_paused(void) static inline bool kvm_check_and_clear_guest_paused(void)
{ {
return false; return false;

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@ -193,6 +193,11 @@ static inline unsigned int kvm_arch_para_features(void)
return 0; return 0;
} }
static inline unsigned int kvm_arch_para_hints(void)
{
return 0;
}
static inline bool kvm_check_and_clear_guest_paused(void) static inline bool kvm_check_and_clear_guest_paused(void)
{ {
return false; return false;

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@ -88,6 +88,7 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned long p1,
#ifdef CONFIG_KVM_GUEST #ifdef CONFIG_KVM_GUEST
bool kvm_para_available(void); bool kvm_para_available(void);
unsigned int kvm_arch_para_features(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_wait(u32 token, int interrupt_kernel);
void kvm_async_pf_task_wake(u32 token); void kvm_async_pf_task_wake(u32 token);
u32 kvm_read_and_reset_pf_reason(void); u32 kvm_read_and_reset_pf_reason(void);
@ -115,6 +116,11 @@ static inline unsigned int kvm_arch_para_features(void)
return 0; return 0;
} }
static inline unsigned int kvm_arch_para_hints(void)
{
return 0;
}
static inline u32 kvm_read_and_reset_pf_reason(void) static inline u32 kvm_read_and_reset_pf_reason(void)
{ {
return 0; return 0;

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@ -10,8 +10,10 @@
*/ */
#define KVM_CPUID_SIGNATURE 0x40000000 #define KVM_CPUID_SIGNATURE 0x40000000
/* This CPUID returns a feature bitmap in eax. Before enabling a particular /* This CPUID returns two feature bitmaps in eax, edx. Before enabling
* paravirtualization, the appropriate feature bit should be checked. * 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_CPUID_FEATURES 0x40000001
#define KVM_FEATURE_CLOCKSOURCE 0 #define KVM_FEATURE_CLOCKSOURCE 0
@ -28,6 +30,8 @@
#define KVM_FEATURE_PV_TLB_FLUSH 9 #define KVM_FEATURE_PV_TLB_FLUSH 9
#define KVM_FEATURE_ASYNC_PF_VMEXIT 10 #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 /* 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. * in pvclock structure. If no bits are set, all flags are ignored.
*/ */

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@ -605,6 +605,11 @@ unsigned int kvm_arch_para_features(void)
return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES); 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) static uint32_t __init kvm_detect(void)
{ {
return kvm_cpuid_base(); return kvm_cpuid_base();

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@ -19,6 +19,11 @@ static inline unsigned int kvm_arch_para_features(void)
return 0; return 0;
} }
static inline unsigned int kvm_arch_para_hints(void)
{
return 0;
}
static inline bool kvm_para_available(void) static inline bool kvm_para_available(void)
{ {
return false; return false;

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@ -9,4 +9,9 @@ static inline bool kvm_para_has_feature(unsigned int feature)
{ {
return !!(kvm_arch_para_features() & (1UL << 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 */ #endif /* __LINUX_KVM_PARA_H */