linux-kernel - [PATCH v1] kvm: x86: Revise guest_fpu xcomp

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Message-Id: <20210208161659.63020-1-jing2.liu@linux.intel.com>
Date:   Mon,  8 Feb 2021 11:16:59 -0500
From:   Jing Liu <jing2.liu@...ux.intel.com>
To:     pbonzini@...hat.com
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] kvm: x86: Revise guest_fpu xcomp_bv field

Bit 63 of the XCOMP_BV field indicates that the save area is in the
compacted format and the remaining bits indicate the states that have
space allocated in the save area, not only user states. Since
fpstate_init() has initialized xcomp_bv, let's just use that.

Signed-off-by: Jing Liu <jing2.liu@...ux.intel.com>
---
 arch/x86/kvm/x86.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1b404e4d7dd8..f115493f577d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4435,8 +4435,6 @@ static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
-#define XSTATE_COMPACTION_ENABLED (1ULL << 63)
-
 static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)
 {
 	struct xregs_state *xsave = &vcpu->arch.guest_fpu->state.xsave;
@@ -4494,7 +4492,8 @@ static void load_xsave(struct kvm_vcpu *vcpu, u8 *src)
 	/* Set XSTATE_BV and possibly XCOMP_BV.  */
 	xsave->header.xfeatures = xstate_bv;
 	if (boot_cpu_has(X86_FEATURE_XSAVES))
-		xsave->header.xcomp_bv = host_xcr0 | XSTATE_COMPACTION_ENABLED;
+		xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
+					 xfeatures_mask_all;
 
 	/*
 	 * Copy each region from the non-compacted offset to the
@@ -9912,9 +9911,6 @@ static void fx_init(struct kvm_vcpu *vcpu)
 		return;
 
 	fpstate_init(&vcpu->arch.guest_fpu->state);
-	if (boot_cpu_has(X86_FEATURE_XSAVES))
-		vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv =
-			host_xcr0 | XSTATE_COMPACTION_ENABLED;
 
 	/*
 	 * Ensure guest xcr0 is valid for loading
-- 
2.18.4