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[Qemu-devel] 答复: Re: [PATCH] target-i386:kvm_get/put_vcpu_events don't h
From: |
peng.hao2 |
Subject: |
[Qemu-devel] 答复: Re: [PATCH] target-i386:kvm_get/put_vcpu_events don't handlesipi_vector |
Date: |
Thu, 13 Jul 2017 10:53:57 +0800 (CST) |
发件人: <address@hidden>
收件人:彭浩10096742 <address@hidden> <address@hidden> <address@hidden>
<address@hidden>
抄送人: <address@hidden> <address@hidden>
日 期 :2017年07月13日 01:01
主 题 :Re: [PATCH] target-i386:kvm_get/put_vcpu_events don't handlesipi_vector
On 12/07/2017 11:12, Peng Hao wrote:
> qemu call kvm_get_vcpu_events, and kernel return sipi_vector always 0,
> never valid when reporting to user space. But qemu call kvm_put_vcpu_events
> will make sipi_vector in kernel be 0. This will accidently modify sipi_vector
> when sipi_vector in kernel is not 0.
>
> Signed-off-by: Peng Hao <address@hidden>
> Reviewed-by: Wang Yechao <address@hidden>
> ---
> target/i386/kvm.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index f84a49d..bbbd696 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -2417,7 +2417,6 @@ static int kvm_put_vcpu_events(X86CPU *cpu, int level)
> events.nmi.masked = !!(env->hflags2 & HF2_NMI_MASK)
> events.nmi.pad = 0
>
> - events.sipi_vector = env->sipi_vector
> events.flags = 0
>
> if (has_msr_smbase) {
This should clear KVM_VCPUEVENT_VALID_SIPI_VECTOR in the "if" statement
below. Otherwise, you're passing a random value to the kernel.
---yes,you're right.I lost this )
> @@ -2506,8 +2505,6 @@ static int kvm_get_vcpu_events(X86CPU *cpu)
> }
> }
>
> - env->sipi_vector = events.sipi_vector
> -
> return 0
> }
>
>
I think what you're seeing is a race like this:
VCPU 0 VCPU 1
[qemu] kvm_get_mp_state
[kvm] kvm_apic_accept_events
__apic_accept_irq
set KVM_APIC_SIPI
[qemu] kvm_get_vcpu_events
----I don't think it will happen.
If this is what happens happen, the fix is to call the functions in this
order:
- first kvm_get_vcpu_events
- then kvm_get_mp_state
- then all the others.
This way you have:
VCPU 0 VCPU 1
[qemu] kvm_get_vcpu_events
__apic_accept_irq
set KVM_APIC_SIPI
[qemu] kvm_get_mp_state
[kvm] kvm_apic_accept_events
[kvm] kvm_vcpu_deliver_sipi_vector
// this modifies CS and RIP!!!
[qemu] kvm_getput_regs
// reads RIP
...
[qemu] kvm_getput_sregs
// reads CS
...
and the sipi_vector is never lost.
----I suspect that sipi_vector is lost when hotplug cpu in some time.
VCPU0 VCPU1 (hotplug)
[kvm]apic_send_ipi
[kvm]set vcpu1.sipi_vector
[kvm] wakeup vcpu1 thread [qemu] kvm_put_vcpu_events
[kvm] set vcpu1.sipi_vector=0
[kvm] kvm_apic_accept_events
[kvm]kvm_vcpu_deliver_sipi_vector(sipi_vector=0)
- [Qemu-devel] 答复: Re: [PATCH] target-i386:kvm_get/put_vcpu_events don't handlesipi_vector,
peng.hao2 <=