[PATCH 5.17 124/158] kvm: x86/pmu: Fix the compare function used by the pmu event filter

Greg Kroah-Hartman
2022-05-23T18:08:54Z

From: Aaron Lewis <aaronlewis@google.com>

[ Upstream commit 4ac19ead0dfbabd8e0bfc731f507cfb0b95d6c99 ]

When returning from the compare function the u64 is truncated to an
int. This results in a loss of the high nybble[1] in the event select
and its sign if that nybble is in use. Switch from using a result that
can end up being truncated to a result that can only be: 1, 0, -1.

[1] bits 35:32 in the event select register and bits 11:8 in the event
select.

Fixes: 7ff775aca48ad ("KVM: x86/pmu: Use binary search to check filtered events")
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220517051238.2566934-1-aaronlewis@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/pmu.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index eca39f56c231..0604bc29f0b8 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -171,9 +171,12 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc)
return true;
}

-static int cmp_u64(const void *a, const void *b)
+static int cmp_u64(const void *pa, const void *pb)
{
- return *(__u64 *)a - *(__u64 *)b;
+ u64 a = *(u64 *)pa;
+ u64 b = *(u64 *)pb;
+
+ return (a > b) - (a < b);
}

void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel)
--
2.35.1