lkml.org 
[lkml]   [2022]   [Dec]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] KVM: x86: ioapic: Fix level-triggered EOI and userspace IOAPIC reconfigure race
From
Date
On Wed, 2022-12-07 at 09:13 +0000, Adamos Ttofari wrote:
> When split-irqchip is used KVM uses ioapic_handled_vectors to identify
> which vectors require an exit to userspace IOAPIC. Unfortunately, when the
> IOAPIC is reconfigured while the interrupt is being handled, it will use
> the newest configuration; therefore, the EOI will not be delivered to
> IOAPIC.
>
> A previous commit 0fc5a36dd6b3
> ("KVM: x86: ioapic: Fix level-triggered EOI and IOAPIC reconfigure race")
> fixed the race for kernel ioapic, but the issue still persists for
> userspace IOAPIC:
>
> 1) Userspace IOAPIC sends a level triggered interrupt to VCPU0.
> 2) VCPU0's handler reconfigures the IOAPIC to route the interrupts to
> VCPU1. (This can cause userspace IOAPIC to commit a new routing table,
> eventually leading KVM to unset the vector in ioapic_handled_vectors)
> 3) VCPU0 triggers an EOI, and it's not delivered to userspace IOAPIC
> because the vector bit is not set in ioapic_handled_vectors.
> 4) The loss of EOI, leaves remote_irr in IOAPIC set. Eventually blocking
> new interrupts.
>
> To avoid the above scenario, we should apply a similar fix like
> commit 0fc5a36dd6b3 ("KVM: x86: ioapic: Fix level-triggered EOI and IOAPIC
> reconfigure race") Which is to add all pending and running vectors to
> ioapic_handled_vectors.
>
> Fixes: 0fc5a36dd6b3 ("KVM: x86: ioapic: Fix level-triggered EOI and IOAPIC reconfigure race")
>
> Signed-off-by: Adamos Ttofari <attofari@amazon.de>

Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>

Thanks.

This should fix https://gitlab.com/kvm-unit-tests/kvm-unit-tests/-/issues/1
shouldn't it?
[unhandled content-type:application/pkcs7-signature]
\
 
 \ /
  Last update: 2022-12-07 10:43    [W:0.613 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site