linux-kernel - [PATCH] do not keep interrupt window closed by sti in real mode

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Date:	Wed,  8 Apr 2009 00:23:37 -0300
From:	Glauber Costa <glommer@...hat.com>
To:	kvm@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, avi@...hat.com
Subject: [PATCH] do not keep interrupt window closed by sti in real mode

While in real mode, sti does not block interrupts from the subsequent
instruction. This is stated at Intel SDM Volume 2b, page 4-432

Without this patch, I cannot boot gpxe option roms at vmx machines.
This is described at https://bugzilla.redhat.com/show_bug.cgi?id=494469

Signed-off-by: Glauber Costa <glommer@...hat.com>
---
 arch/x86/kvm/vmx.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c6997c0..51e0b8a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2490,18 +2490,19 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
 static void vmx_update_window_states(struct kvm_vcpu *vcpu)
 {
 	u32 guest_intr = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO);
+	int rmode = vcpu->arch.rmode.active;
 
 	vcpu->arch.nmi_window_open =
-		!(guest_intr & (GUEST_INTR_STATE_STI |
-				GUEST_INTR_STATE_MOV_SS |
+		(rmode || !(guest_intr & GUEST_INTR_STATE_STI)) &&
+		!(guest_intr & (GUEST_INTR_STATE_MOV_SS |
 				GUEST_INTR_STATE_NMI));
 	if (!cpu_has_virtual_nmis() && to_vmx(vcpu)->soft_vnmi_blocked)
 		vcpu->arch.nmi_window_open = 0;
 
 	vcpu->arch.interrupt_window_open =
 		((vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) &&
-		 !(guest_intr & (GUEST_INTR_STATE_STI |
-				 GUEST_INTR_STATE_MOV_SS)));
+		(rmode || !(guest_intr & GUEST_INTR_STATE_STI)) &&
+		 !(guest_intr & GUEST_INTR_STATE_MOV_SS));
 }
 
 static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu)
-- 
1.6.2

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