linux-kernel - [PATCH v4 3/5] KVM: selftests: aarch64: Fix the buggy [enable|disable]

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Date: Thu,  1 Feb 2024 21:56:52 -0500
From: Shaoqin Huang <shahuang@...hat.com>
To: Oliver Upton <oliver.upton@...ux.dev>,
	Marc Zyngier <maz@...nel.org>,
	kvmarm@...ts.linux.dev
Cc: Eric Auger <eauger@...hat.com>,
	Shaoqin Huang <shahuang@...hat.com>,
	Eric Auger <eric.auger@...hat.com>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Shuah Khan <shuah@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v4 3/5] KVM: selftests: aarch64: Fix the buggy [enable|disable]_counter

In general, the set/clr registers should always be used in their
write form, never in a RMW form (imagine an interrupt disabling
a counter between the read and the write...).

The current implementation of [enable|disable]_counter both use the RMW
form, fix them by directly write to the set/clr registers.

At the same time, it also fix the buggy disable_counter() which would
end up disabling all the counters.

Signed-off-by: Shaoqin Huang <shahuang@...hat.com>
Reviewed-by: Eric Auger <eric.auger@...hat.com>
---
 tools/testing/selftests/kvm/include/aarch64/vpmu.h | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/aarch64/vpmu.h b/tools/testing/selftests/kvm/include/aarch64/vpmu.h
index f78c93a08bff..92715021f892 100644
--- a/tools/testing/selftests/kvm/include/aarch64/vpmu.h
+++ b/tools/testing/selftests/kvm/include/aarch64/vpmu.h
@@ -77,17 +77,13 @@ static inline void write_sel_evtyper(int sel, unsigned long val)
 
 static inline void enable_counter(int idx)
 {
-	uint64_t v = read_sysreg(pmcntenset_el0);
-
-	write_sysreg(BIT(idx) | v, pmcntenset_el0);
+	write_sysreg(BIT(idx), pmcntenset_el0);
 	isb();
 }
 
 static inline void disable_counter(int idx)
 {
-	uint64_t v = read_sysreg(pmcntenset_el0);
-
-	write_sysreg(BIT(idx) | v, pmcntenclr_el0);
+	write_sysreg(BIT(idx), pmcntenclr_el0);
 	isb();
 }
 
-- 
2.40.1