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From: Sean Christopherson <seanjc@google.com>
To: Michal Luczaj <mhal@rbox.co>
Cc: kvm@vger.kernel.org, pbonzini@redhat.com
Subject: Re: [PATCH 8/8] KVM: x86: Fix NULL pointer dereference in kvm_xen_set_evtchn_fast()
Date: Thu, 13 Oct 2022 20:28:47 +0000	[thread overview]
Message-ID: <Y0h0/x3Fvn17zVt6@google.com> (raw)
In-Reply-To: <Y0daPIFwmosxV/NO@google.com>

On Thu, Oct 13, 2022, Sean Christopherson wrote:
> On Mon, Oct 10, 2022, Sean Christopherson wrote:
> > On Wed, Sep 21, 2022, Michal Luczaj wrote:
> > If this fixes things on your end (I'll properly test tomorrow too), I'll post a
> > v2 of the entire series.  There are some cleanups that can be done on top, e.g.
> > I think we should drop kvm_gpc_unmap() entirely until there's actually a user,
> > because it's not at all obvious that it's (a) necessary and (b) has desirable
> > behavior.
> 
> Sorry for the delay, I initially missed that you included a selftest for the race
> in the original RFC.  The kernel is no longer exploding, but the test is intermittently
> soft hanging waiting for the "IRQ".  I'll debug and hopefully post tomorrow.

Ended up being a test bug (technically).  KVM drops the timer IRQ if the shared
info page is invalid.  As annoying as that is, there's isn't really a better
option, and invalidating a shared page while vCPUs are running really is a VMM
bug.

To fix, I added an intermediate stage in the test that re-arms the timer if the
IRQ doesn't arrive in a reasonable amount of time.

Patches incoming...

  reply	other threads:[~2022-10-13 20:28 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-16  0:54 [RFC PATCH 0/4] KVM: x86/xen: shinfo cache lock corruption Michal Luczaj
2022-09-16  0:54 ` [RFC PATCH 1/4] KVM: x86/xen: Ensure kvm_xen_set_evtchn_fast() can use shinfo_cache Michal Luczaj
2022-09-16  0:54 ` [RFC PATCH 2/4] KVM: x86/xen: Ensure kvm_xen_schedop_poll() " Michal Luczaj
2022-09-16  0:54 ` [RFC PATCH 3/4] KVM: x86/xen: Disallow gpc locks reinitialization Michal Luczaj
2022-09-16 17:12   ` Sean Christopherson
2022-09-18 23:13     ` Michal Luczaj
2022-09-21  2:01     ` [PATCH 0/8] KVM: x86: gfn_to_pfn_cache cleanups and a fix Michal Luczaj
2022-09-21  2:01       ` [PATCH 1/8] KVM: x86: Add initializer for gfn_to_pfn_cache Michal Luczaj
2022-10-10 23:38         ` Sean Christopherson
2022-09-21  2:01       ` [PATCH 2/8] KVM: x86: Shorten gfn_to_pfn_cache function names Michal Luczaj
2022-09-21  2:01       ` [PATCH 3/8] KVM: x86: Remove unused argument in gpc_unmap_khva() Michal Luczaj
2022-09-21  2:01       ` [PATCH 4/8] KVM: x86: Store immutable gfn_to_pfn_cache properties Michal Luczaj
2022-10-10 23:42         ` Sean Christopherson
2022-10-11  0:37         ` Sean Christopherson
2022-09-21  2:01       ` [PATCH 5/8] KVM: x86: Clean up kvm_gpc_check() Michal Luczaj
2022-09-21  2:01       ` [PATCH 6/8] KVM: x86: Clean up hva_to_pfn_retry() Michal Luczaj
2022-09-21  2:01       ` [PATCH 7/8] KVM: x86: Clean up kvm_gpc_refresh(), kvm_gpc_unmap() Michal Luczaj
2022-09-21  2:01       ` [PATCH 8/8] KVM: x86: Fix NULL pointer dereference in kvm_xen_set_evtchn_fast() Michal Luczaj
2022-10-10 23:28         ` Sean Christopherson
2022-10-13  0:22           ` Sean Christopherson
2022-10-13 20:28             ` Sean Christopherson [this message]
2022-10-20 15:59               ` Michal Luczaj
2022-10-20 16:58                 ` Sean Christopherson
2022-10-21  2:39                   ` Michal Luczaj
2022-10-05 12:30     ` [PATCH v2 0/8] KVM: x86: gfn_to_pfn_cache cleanups and a fix Michal Luczaj
2022-10-05 12:30       ` [PATCH v2 1/8] KVM: x86: Add initializer for gfn_to_pfn_cache Michal Luczaj
2022-10-05 12:30       ` [PATCH v2 2/8] KVM: x86: Shorten gfn_to_pfn_cache function names Michal Luczaj
2022-10-05 12:30       ` [PATCH v2 3/8] KVM: x86: Remove unused argument in gpc_unmap_khva() Michal Luczaj
2022-10-05 12:30       ` [PATCH v2 4/8] KVM: x86: Store immutable gfn_to_pfn_cache properties Michal Luczaj
2022-10-05 12:30       ` [PATCH v2 5/8] KVM: x86: Clean up kvm_gpc_check() Michal Luczaj
2022-10-05 12:30       ` [PATCH v2 6/8] KVM: x86: Clean up hva_to_pfn_retry() Michal Luczaj
2022-10-05 12:30       ` [PATCH v2 7/8] KVM: x86: Clean up kvm_gpc_refresh(), kvm_gpc_unmap() Michal Luczaj
2022-10-05 12:30       ` [PATCH v2 8/8] KVM: x86: Fix NULL pointer dereference in kvm_xen_set_evtchn_fast() Michal Luczaj
2022-09-16  0:54 ` [RFC PATCH 4/4] KVM: x86/xen: Test shinfo_cache lock races Michal Luczaj

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