linux-kernel - [PATCH 1/3] KVM: x86: expose UMWAIT/UMONITOR/TPAUSE CPU features into VM.

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Date:   Tue, 10 Jul 2018 16:54:41 +0800
From:   Jingqi Liu <jingqi.liu@...el.com>
To:     pbonzini@...hat.com, rkrcmar@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com
Cc:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        wei.w.wang@...el.com, Jingqi Liu <jingqi.liu@...el.com>
Subject: [PATCH 1/3] KVM: x86: expose UMWAIT/UMONITOR/TPAUSE CPU features into VM.

UMONITOR, UMWAIT, and TPAUSE are a set of user wait instructions.

UMONITOR arms address monitoring hardware using an address. A store
to an address within the specified address range triggers the
monitoring hardware to wake up the processor waiting in umwait.

UMWAIT instructs the processor to enter an implementation-dependent
optimized state while monitoring a range of addresses. The optimized
state may be either a light-weight power/performance optimized state
(c0.1 state) or an improved power/performance optimized state
(c0.2 state).

TPAUSE instructs the processor to enter an implementation-dependent
optimized state c0.1 or c0.2 state and wake up when time-stamp counter
reaches specified timeout.

Availability of the user wait instructions is indicated by the presence
of the CPUID feature flag WAITPKG CPUID.0x07.0x0:ECX[5].

This patch exposes the umonitor,umwait, and tpause features to the guest.

The release document ref below link:
https://software.intel.com/sites/default/files/managed/c5/15/\
architecture-instruction-set-extensions-programming-reference.pdf
This patch has a dependency on https://lkml.org/lkml/2018/6/15/657.

Signed-off-by: Jingqi Liu <jingqi.liu@...el.com>
---
 arch/x86/kvm/cpuid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 7e042e3..e16c05e 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -406,7 +406,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 		F(AVX512VBMI) | F(LA57) | F(PKU) | 0 /*OSPKE*/ |
 		F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |
 		F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |
-		F(CLDEMOTE);
+		F(CLDEMOTE) | F(WAITPKG);

 	/* cpuid 7.0.edx*/
 	const u32 kvm_cpuid_7_0_edx_x86_features =
-- 
1.8.3.1