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

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

[gregkh]

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 <stable@vger.kernel.org> know about it.


>From 00c87e9a70a17b355b81c36adedf05e84f54e10d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>
Date: Wed, 1 Feb 2017 14:19:53 +0100
Subject: KVM: x86: do not save guest-unsupported XSAVE state
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Radim Krčmář <rkrcmar@redhat.com>

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.

Fixes: df1daba7d1cb ("KVM: x86: support XSAVES usage in the host")
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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 rkrcmar@redhat.com are

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