Re: [PATCH] fix -no-kvm-irqchip regression

[Avi Kivity <avi@qumranet.com>]

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Andrea Arcangeli wrote:
> On Wed, Aug 13, 2008 at 10:05:06AM +0200, Jan Kiszka wrote:
>   
>> Should this issue have been fixed meanwhile? I just gave latest git a
>> try and - as far as I recall my tests before holiday correctly - things
>> look the same. At least some Linux 2.6.23 kernel still hangs here during
>> early boot with -no-kvm-irqchip.
>>     
>
> The trouble was that clearing the idt_vectoring_info before handling
> the exit_reason would lead to the handle_exception to fail setting the
> irq_pending bit because is_external_interrupt was run on zero instead
> of the vmcs IDT_VECTORING_INFO_FIELD, so it didn't notice it was an
> external interrupt generating the exit.
>
> This makes the userland irqchip code work again for me, there seem to
> be no good reason to clear this value before returning in guest mode
> and only setting it to zero didn't look an effective debugging aid, so
> it's a microoptimization for the kernel irqchip too.
>   

I don't like the usage of idt_vectoring_info; so I've switched the 
!irqchip_in_kernel path to use the interrupt queue.  Attached patch 
boots Windows XP ACPI here.

Will push it out once it passes regression testing.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.


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>From 37304c6f9ced347cf013bcd4bf808d6fd4fb6ce1 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@qumranet.com>
Date: Thu, 14 Aug 2008 11:13:16 +0300
Subject: [PATCH] KVM: VMX: Use interrupt queue for !irqchip_in_kernel

Signed-off-by: Avi Kivity <avi@qumranet.com>
---
 arch/x86/kvm/vmx.c |   11 +++++------
 1 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 337670b..8693fb5 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2173,7 +2173,7 @@ static void kvm_do_inject_irq(struct kvm_vcpu *vcpu)
 	clear_bit(bit_index, &vcpu->arch.irq_pending[word_index]);
 	if (!vcpu->arch.irq_pending[word_index])
 		clear_bit(word_index, &vcpu->arch.irq_summary);
-	vmx_inject_irq(vcpu, irq);
+	kvm_queue_interrupt(vcpu, irq);
 }
 
 
@@ -2187,13 +2187,12 @@ static void do_interrupt_requests(struct kvm_vcpu *vcpu,
 		 (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & 3) == 0);
 
 	if (vcpu->arch.interrupt_window_open &&
-	    vcpu->arch.irq_summary &&
-	    !(vmcs_read32(VM_ENTRY_INTR_INFO_FIELD) & INTR_INFO_VALID_MASK))
-		/*
-		 * If interrupts enabled, and not blocked by sti or mov ss. Good.
-		 */
+	    vcpu->arch.irq_summary && !vcpu->arch.interrupt.pending)
 		kvm_do_inject_irq(vcpu);
 
+	if (vcpu->arch.interrupt_window_open && vcpu->arch.interrupt.pending)
+		vmx_inject_irq(vcpu, vcpu->arch.interrupt.nr);
+
 	cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
 	if (!vcpu->arch.interrupt_window_open &&
 	    (vcpu->arch.irq_summary || kvm_run->request_interrupt_window))
-- 
1.5.6.3