[4.2.y-ckt stable] Patch "KVM: x86: fix ordering of cr0 initialization code in vmx_cpu_reset" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

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

    KVM: x86: fix ordering of cr0 initialization code in vmx_cpu_reset

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt12.

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

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From 5b342956efe4831ed898720f9cf4294d120a2ca5 Mon Sep 17 00:00:00 2001
From: Bruce Rogers <brogers at suse.com>
Date: Thu, 28 Apr 2016 14:49:21 -0600
Subject: KVM: x86: fix ordering of cr0 initialization code in vmx_cpu_reset
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit f24632475d4ffed5626abbfab7ef30a128dd1474 upstream.

Commit d28bc9dd25ce reversed the order of two lines which initialize cr0,
allowing the current (old) cr0 value to mess up vcpu initialization.
This was observed in the checks for cr0 X86_CR0_WP bit in the context of
kvm_mmu_reset_context(). Besides, setting vcpu->arch.cr0 after vmx_set_cr0()
is completely redundant. Change the order back to ensure proper vcpu
initialization.

The combination of booting with ovmf firmware when guest vcpus > 1 and kvm's
ept=N option being set results in a VM-entry failure. This patch fixes that.

Fixes: d28bc9dd25ce ("KVM: x86: INIT and reset sequences are different")
Signed-off-by: Bruce Rogers <brogers at suse.com>
Signed-off-by: Radim Krčmář <rkrcmar at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/x86/kvm/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c832c7d..8f30efc 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4795,8 +4795,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 		vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->vpid);

 	cr0 = X86_CR0_NW | X86_CR0_CD | X86_CR0_ET;
-	vmx_set_cr0(vcpu, cr0); /* enter rmode */
 	vmx->vcpu.arch.cr0 = cr0;
+	vmx_set_cr0(vcpu, cr0); /* enter rmode */
 	vmx_set_cr4(vcpu, 0);
 	vmx_set_efer(vcpu, 0);
 	vmx_fpu_activate(vcpu);
--
2.7.4