[PATCH 1/3] kvm: x86/pmu: Fix the compare function used by the pmu event filter

[Aaron Lewis <aaronlewis@google.com>]

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>
---
 arch/x86/kvm/pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index eca39f56c231..1666e9d3e545 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -173,7 +173,7 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc)
 
 static int cmp_u64(const void *a, const void *b)
 {
-	return *(__u64 *)a - *(__u64 *)b;
+	return (*(u64 *)a > *(u64 *)b) - (*(u64 *)a < *(u64 *)b);
 }
 
 void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel)
-- 
2.36.1.124.g0e6072fb45-goog