linux-kernel - [PATCH 4.4 08/50] KVM: s390: correct fprs on SIGP (STOP AND) STORE STATUS

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Message-Id: <20160314175014.586743283@linuxfoundation.org>
Date:	Mon, 14 Mar 2016 10:50:26 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Christian Borntraeger <borntraeger@...ibm.com>,
	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.4 08/50] KVM: s390: correct fprs on SIGP (STOP AND) STORE STATUS

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Hildenbrand <dahi@...ux.vnet.ibm.com>

commit 9522b37f5a8c7bfabe46eecadf2e130f1103f337 upstream.

With MACHINE_HAS_VX, we convert the floating point registers from the
vector registeres when storing the status. For other VCPUs, these are
stored to vcpu->run->s.regs.vrs, but we are using current->thread.fpu.vxrs,
which resolves to the currently loaded VCPU.

So kvm_s390_store_status_unloaded() currently writes the wrong floating
point registers (converted from the vector registers) when called from
another VCPU on a z13.

This is only the case for old user space not handling SIGP STORE STATUS and
SIGP STOP AND STORE STATUS, but relying on the kernel implementation. All
other calls come from the loaded VCPU via kvm_s390_store_status().

Fixes: 9abc2a08a7d6 (KVM: s390: fix memory overwrites when vx is disabled)
Reviewed-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: David Hildenbrand <dahi@...ux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/s390/kvm/kvm-s390.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2249,7 +2249,7 @@ int kvm_s390_store_status_unloaded(struc

 	/* manually convert vector registers if necessary */
 	if (MACHINE_HAS_VX) {
-		convert_vx_to_fp(fprs, current->thread.fpu.vxrs);
+		convert_vx_to_fp(fprs, (__vector128 *) vcpu->run->s.regs.vrs);
 		rc = write_guest_abs(vcpu, gpa + __LC_FPREGS_SAVE_AREA,
 				     fprs, 128);
 	} else {