[ 3.8.y.z extended stable ] Patch "KVM: s390: move kvm_guest_enter, exit closer to sie" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    KVM: s390: move kvm_guest_enter,exit closer to sie

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From a33e06eba433231d9d5087833b789f41db027781 Mon Sep 17 00:00:00 2001
From: Dominik Dingel <dingel at linux.vnet.ibm.com>
Date: Fri, 26 Jul 2013 15:04:00 +0200
Subject: KVM: s390: move kvm_guest_enter,exit closer to sie

commit 2b29a9fdcb92bfc6b6f4c412d71505869de61a56 upstream.

Any uaccess between guest_enter and guest_exit could trigger a page fault,
the page fault handler would handle it as a guest fault and translate a
user address as guest address.

Signed-off-by: Dominik Dingel <dingel at linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger at de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
[ kamal: backport to 3.8 (context) ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/s390/kvm/kvm-s390.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 8bafa4f..74e64f8 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -613,14 +613,25 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 		kvm_s390_deliver_pending_interrupts(vcpu);

 	vcpu->arch.sie_block->icptcode = 0;
-	preempt_disable();
-	kvm_guest_enter();
-	preempt_enable();
 	VCPU_EVENT(vcpu, 6, "entering sie flags %x",
 		   atomic_read(&vcpu->arch.sie_block->cpuflags));
 	trace_kvm_s390_sie_enter(vcpu,
 				 atomic_read(&vcpu->arch.sie_block->cpuflags));
+
+	/*
+	 * As PF_VCPU will be used in fault handler, between guest_enter
+	 * and guest_exit should be no uaccess.
+	 */
+	preempt_disable();
+	kvm_guest_enter();
+	preempt_enable();
 	rc = sie64a(vcpu->arch.sie_block, vcpu->run->s.regs.gprs);
+	kvm_guest_exit();
+
+	VCPU_EVENT(vcpu, 6, "exit sie icptcode %d",
+		   vcpu->arch.sie_block->icptcode);
+	trace_kvm_s390_sie_exit(vcpu, vcpu->arch.sie_block->icptcode);
+
 	if (rc) {
 		if (kvm_is_ucontrol(vcpu->kvm)) {
 			rc = SIE_INTERCEPT_UCONTROL;
@@ -631,10 +642,6 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 			rc = 0;
 		}
 	}
-	VCPU_EVENT(vcpu, 6, "exit sie icptcode %d",
-		   vcpu->arch.sie_block->icptcode);
-	trace_kvm_s390_sie_exit(vcpu, vcpu->arch.sie_block->icptcode);
-	kvm_guest_exit();

 	memcpy(&vcpu->run->s.regs.gprs[14], &vcpu->arch.sie_block->gg14, 16);
 	return rc;
--
1.8.1.2