linux-kernel - [PATCH] KVM: x86: do not save guest-unsupported XSAVE state

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Message-Id: <20170201131953.30098-1-rkrcmar@redhat.com>
Date:   Wed,  1 Feb 2017 14:19:53 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH] KVM: x86: do not save guest-unsupported XSAVE state

Saving unsupported state prevents migration when the new host does not
support a XSAVE feature of the original host, even if the feature is not
exposed to the guest.

We've masked host features with guest-visible features before, with
4344ee981e21 ("KVM: x86: only copy XSAVE state for the supported
features") and dropped it when implementing XSAVES.  Do it again.

Fixes: df1daba7d1cb ("KVM: x86: support XSAVES usage in the host")
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 arch/x86/kvm/x86.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 96dd7dd13ee6..5f013ad89b57 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3221,6 +3221,7 @@ static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)
 	memcpy(dest, xsave, XSAVE_HDR_OFFSET);
 
 	/* Set XSTATE_BV */
+	xstate_bv &= vcpu->arch.guest_supported_xcr0 | XFEATURE_MASK_FPSSE;
 	*(u64 *)(dest + XSAVE_HDR_OFFSET) = xstate_bv;
 
 	/*
-- 
2.11.0