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authorWanpeng Li <wanpengli@tencent.com>2018-02-13 04:05:40 +0300
committerRadim Krčmář <rkrcmar@redhat.com>2018-03-06 20:40:44 +0300
commita4429e53c9b3082b05e51224c3d58dbdd39306c5 (patch)
treed0fbeff12679477198902c365cb23ad6b645747c
parentd4c67a7a54f12cb8d267284212f1072c95917e5a (diff)
downloadlinux-a4429e53c9b3082b05e51224c3d58dbdd39306c5.tar.xz
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>
-rw-r--r--Documentation/virtual/kvm/cpuid.txt15
-rw-r--r--arch/mips/include/asm/kvm_para.h5
-rw-r--r--arch/powerpc/include/asm/kvm_para.h5
-rw-r--r--arch/s390/include/asm/kvm_para.h5
-rw-r--r--arch/x86/include/asm/kvm_para.h6
-rw-r--r--arch/x86/include/uapi/asm/kvm_para.h8
-rw-r--r--arch/x86/kernel/kvm.c5
-rw-r--r--include/asm-generic/kvm_para.h5
-rw-r--r--include/linux/kvm_para.h5
9 files changed, 55 insertions, 4 deletions
diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt
index 87a7506f31c2..d4f33eb805dd 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 60b1aa0b7014..b57e978b0946 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 336a91acb8b1..5ceb4efca65f 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 74eeec9c0a80..cbc7c3a68e4d 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 7b407dda2bd7..3aea2658323a 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 6cfa9c8cb7d6..68a41b6ba3da 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 bc1a27280c4b..8c9d98c46f84 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 18c6abe81fbd..728e5c5706c4 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 51f6ef2c2ff4..f23b90b02898 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 */