From: Bandan Das <bsd@redhat.com>
To: Wanpeng Li <wanpeng.li@linux.intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Jan Kiszka <jan.kiszka@siemens.com>,
Gleb Natapov <gleb@kernel.org>, Hu Robert <robert.hu@intel.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since race
Date: Wed, 02 Jul 2014 12:27:59 -0400 [thread overview]
Message-ID: <jpg7g3v7mk0.fsf@redhat.com> (raw)
In-Reply-To: <1404284054-51863-1-git-send-email-wanpeng.li@linux.intel.com> (Wanpeng Li's message of "Wed, 2 Jul 2014 14:54:14 +0800")
Wanpeng Li <wanpeng.li@linux.intel.com> writes:
> This patch fix bug https://bugzilla.kernel.org/show_bug.cgi?id=72381
I can also reproduce this easily with Linux as L1 by "slowing it down"
eg. running with ept = 0
I suggest changing the subject to -
KVM: nVMX: Fix race that incorrectly injects L1's irq to L2
> If we didn't inject a still-pending event to L1 since nested_run_pending,
> KVM_REQ_EVENT should be requested after the vmexit in order to inject the
> event to L1. However, current log blindly request a KVM_REQ_EVENT even if
What's current "log" ? Do you mean current "code" ?
> there is no still-pending event to L1 which blocked by nested_run_pending.
> There is a race which lead to an interrupt will be injected to L2 which
> belong to L1 if L0 send an interrupt to L1 during this window.
>
> VCPU0 another thread
>
> L1 intr not blocked on L2 first entry
> vmx_vcpu_run req event
> kvm check request req event
> check_nested_events don't have any intr
> not nested exit
> intr occur (8254, lapic timer etc)
> inject_pending_event now have intr
> inject interrupt
>
> This patch fix this race by introduced a l1_events_blocked field in nested_vmx
> which indicates there is still-pending event which blocked by nested_run_pending,
> and smart request a KVM_REQ_EVENT if there is a still-pending event which blocked
> by nested_run_pending.
>
> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
> ---
> arch/x86/kvm/vmx.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index f4e5aed..fe69c49 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -372,6 +372,7 @@ struct nested_vmx {
> u64 vmcs01_tsc_offset;
> /* L2 must run next, and mustn't decide to exit to L1. */
> bool nested_run_pending;
> + bool l1_events_blocked;
> /*
> * Guest pages referred to in vmcs02 with host-physical pointers, so
> * we must keep them pinned while L2 runs.
> @@ -7380,8 +7381,10 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
> * we did not inject a still-pending event to L1 now because of
> * nested_run_pending, we need to re-enable this bit.
> */
> - if (vmx->nested.nested_run_pending)
> + if (to_vmx(vcpu)->nested.l1_events_blocked) {
Is to_vmx() necessary since we alredy have the vmx pointer ?
> + to_vmx(vcpu)->nested.l1_events_blocked = false;
> kvm_make_request(KVM_REQ_EVENT, vcpu);
> + }
>
> vmx->nested.nested_run_pending = 0;
>
> @@ -8197,15 +8200,20 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr)
>
> if (nested_cpu_has_preemption_timer(get_vmcs12(vcpu)) &&
> vmx->nested.preemption_timer_expired) {
> - if (vmx->nested.nested_run_pending)
> + if (vmx->nested.nested_run_pending) {
> + vmx->nested.l1_events_blocked = true;
> return -EBUSY;
> + }
> nested_vmx_vmexit(vcpu, EXIT_REASON_PREEMPTION_TIMER, 0, 0);
> return 0;
> }
>
> if (vcpu->arch.nmi_pending && nested_exit_on_nmi(vcpu)) {
> - if (vmx->nested.nested_run_pending ||
> - vcpu->arch.interrupt.pending)
> + if (vmx->nested.nested_run_pending) {
> + vmx->nested.l1_events_blocked = true;
> + return -EBUSY;
> + }
> + if (vcpu->arch.interrupt.pending)
> return -EBUSY;
> nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
> NMI_VECTOR | INTR_TYPE_NMI_INTR |
> @@ -8221,8 +8229,10 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr)
>
> if ((kvm_cpu_has_interrupt(vcpu) || external_intr) &&
> nested_exit_on_intr(vcpu)) {
> - if (vmx->nested.nested_run_pending)
> + if (vmx->nested.nested_run_pending) {
> + vmx->nested.l1_events_blocked = true;
> return -EBUSY;
> + }
> nested_vmx_vmexit(vcpu, EXIT_REASON_EXTERNAL_INTERRUPT, 0, 0);
> }
Also, I am wondering isn't it enough to just do this to avoid this race ?
static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu)
{
- return (!to_vmx(vcpu)->nested.nested_run_pending &&
+ return (!is_guest_mode(vcpu) &&
+ !to_vmx(vcpu)->nested.nested_run_pending &&
vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) &&
!(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) &
Thanks,
Bandan
next prev parent reply other threads:[~2014-07-02 16:27 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-02 6:54 [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since race Wanpeng Li
2014-07-02 7:20 ` Hu, Robert
2014-07-02 9:03 ` Jan Kiszka
2014-07-02 9:13 ` Hu, Robert
2014-07-02 9:16 ` Jan Kiszka
2014-07-02 9:01 ` Jan Kiszka
2014-07-03 2:59 ` Wanpeng Li
2014-07-03 5:15 ` Bandan Das
2014-07-03 6:59 ` Wanpeng Li
2014-07-03 17:27 ` Bandan Das
2014-07-04 2:52 ` Wanpeng Li
2014-07-04 5:43 ` Jan Kiszka
2014-07-04 6:08 ` Wanpeng Li
2014-07-04 7:19 ` Jan Kiszka
2014-07-04 7:39 ` Wanpeng Li
2014-07-04 7:46 ` Paolo Bonzini
2014-07-04 7:59 ` Wanpeng Li
2014-07-04 8:14 ` Paolo Bonzini
2014-07-04 8:24 ` Wanpeng Li
2014-07-04 7:42 ` Paolo Bonzini
2014-07-04 9:33 ` Jan Kiszka
2014-07-04 9:38 ` Paolo Bonzini
2014-07-04 10:52 ` Jan Kiszka
2014-07-04 11:07 ` Jan Kiszka
2014-07-04 11:28 ` Paolo Bonzini
2014-07-04 11:46 ` [PATCH] Add -mno-red-zone to CFLAGS for x86-64 Jan Kiszka
2014-07-04 11:49 ` Paolo Bonzini
2014-07-04 6:17 ` [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since race Wanpeng Li
2014-07-04 7:21 ` Jan Kiszka
2014-07-07 0:56 ` Bandan Das
2014-07-07 8:46 ` Wanpeng Li
2014-07-07 13:03 ` Paolo Bonzini
2014-07-07 17:31 ` Bandan Das
2014-07-07 17:34 ` Paolo Bonzini
2014-07-07 17:38 ` Bandan Das
2014-07-07 23:14 ` Wanpeng Li
2014-07-08 4:35 ` Bandan Das
2014-07-07 23:38 ` Wanpeng Li
2014-07-08 5:49 ` Paolo Bonzini
2014-07-02 16:27 ` Bandan Das [this message]
2014-07-03 5:11 ` Wanpeng Li
2014-07-03 5:29 ` Bandan Das
2014-07-03 7:33 ` Jan Kiszka
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=jpg7g3v7mk0.fsf@redhat.com \
--to=bsd@redhat.com \
--cc=gleb@kernel.org \
--cc=jan.kiszka@siemens.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=robert.hu@intel.com \
--cc=wanpeng.li@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox