Commit a4429e53 authored by Wanpeng Li's avatar Wanpeng Li Committed by Radim Krčmář

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: default avatarWanpeng Li <wanpengli@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent d4c67a7a
......@@ -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
----------------------------------------------------------------------------------
......@@ -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)
{
......
......@@ -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;
......
......@@ -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;
......
......@@ -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;
......
......@@ -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.
*/
......
......@@ -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();
......
......@@ -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;
......
......@@ -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 */
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