On Fri, Dec 17, 2021 at 6:05 AM Wei Wang <wei.w.wang@xxxxxxxxx> wrote:
>
> The fixed counter 3 is used for the Topdown metrics, which hasn't been
> enabled for KVM guests. Userspace accessing to it will fail as it's not
> included in get_fixed_pmc(). This breaks KVM selftests on ICX+ machines,
> which have this counter.
>
> To reproduce it on ICX+ machines, ./state_test reports:
> ==== Test Assertion Failure ====
> lib/x86_64/processor.c:1078: r == nmsrs
> pid=4564 tid=4564 - Argument list too long
> 1 0x000000000040b1b9: vcpu_save_state at processor.c:1077
> 2 0x0000000000402478: main at state_test.c:209 (discriminator 6)
> 3 0x00007fbe21ed5f92: ?? ??:0
> 4 0x000000000040264d: _start at ??:?
> Unexpected result from KVM_GET_MSRS, r: 17 (failed MSR was 0x30c)
>
> With this patch, it works well.
>
> Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
Reviewed-and-tested-by: Jim Mattson <jmattson@xxxxxxxxxx>
I believe this fixes commit 2e8cd7a3b828 ("kvm: x86: limit the maximum
number of vPMU fixed counters to 3") from v5.9. Should this be cc'ed
to stable?
