Re: [PATCH 4/7] KVM: x86: SVM: fix avic_kick_target_vcpus_fast

Paolo Bonzini
2022-06-08T13:21:55Z

On 6/6/22 20:08, Maxim Levitsky wrote:
> There are two issues in avic_kick_target_vcpus_fast
>
> 1. It is legal to issue an IPI request with APIC_DEST_NOSHORT
> and a physical destination of 0xFF (or 0xFFFFFFFF in case of x2apic),
> which must be treated as a broadcast destination.
>
> Fix this by explicitly checking for it.
> Also don’t use ‘index’ in this case as it gives no new information.
>
> 2. It is legal to issue a logical IPI request to more than one target.
> Index field only provides index in physical id table of first
> such target and therefore can't be used before we are sure
> that only a single target was addressed.
>
> Instead, parse the ICRL/ICRH, double check that a unicast interrupt
> was requested, and use that info to figure out the physical id
> of the target vCPU.
> At that point there is no need to use the index field as well.
>
>
> In addition to fixing the above issues, also skip the call to
> kvm_apic_match_dest.
>
> It is possible to do this now, because now as long as AVIC is not
> inhibited, it is guaranteed that none of the vCPUs changed their
> apic id from its default value.
>
>
> This fixes boot of windows guest with AVIC enabled because it uses
> IPI with 0xFF destination and no destination shorthand.
>
> Fixes: 7223fd2d5338 ("KVM: SVM: Use target APIC ID to complete AVIC IRQs when possible")
> Cc: stable@vger.kernel.org
>
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>

Is it possible to use kvm_intr_is_single_vcpu_fast, or am I missing
something?

Series queued, thanks.

Paolo