Patch "KVM: x86: do not save guest-unsupported XSAVE state" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

KVM: x86: do not save guest-unsupported XSAVE state

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-x86-do-not-save-guest-unsupported-xsave-state.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <[email protected]>
Date: Wed, 1 Feb 2017 14:19:53 +0100
Subject: KVM: x86: do not save guest-unsupported XSAVE state
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From: Radim Krčmář <[email protected]>

commit 00c87e9a70a17b355b81c36adedf05e84f54e10d upstream.

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.

---
 arch/x86/kvm/x86.c |    1 +
 1 file changed, 1 insertion(+)

@@ -3057,6 +3057,7 @@ static void fill_xsave(u8 *dest, struct
 	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;
 
 	/*

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/kvm-x86-do-not-save-guest-unsupported-xsave-state.patch