linux-kernel - [PATCH v5 08/22] RISC-V: KVM: Fix the initial sample period value

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Message-Id: <20240403080452.1007601-9-atishp@rivosinc.com>
Date: Wed,  3 Apr 2024 01:04:37 -0700
From: Atish Patra <atishp@...osinc.com>
To: linux-kernel@...r.kernel.org
Cc: Atish Patra <atishp@...osinc.com>,
	Ajay Kaher <akaher@...are.com>,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Alexey Makhalov <amakhalov@...are.com>,
	Andrew Jones <ajones@...tanamicro.com>,
	Anup Patel <anup@...infault.org>,
	Conor Dooley <conor.dooley@...rochip.com>,
	Juergen Gross <jgross@...e.com>,
	kvm-riscv@...ts.infradead.org,
	kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	Mark Rutland <mark.rutland@....com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Shuah Khan <shuah@...nel.org>,
	virtualization@...ts.linux.dev,
	VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
	Will Deacon <will@...nel.org>,
	x86@...nel.org
Subject: [PATCH v5 08/22] RISC-V: KVM: Fix the initial sample period value

The initial sample period value when counter value is not assigned
should be set to maximum value supported by the counter width.
Otherwise, it may result in spurious interrupts.

Signed-off-by: Atish Patra <atishp@...osinc.com>
---
 arch/riscv/kvm/vcpu_pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index 86391a5061dd..cee1b9ca4ec4 100644
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -39,7 +39,7 @@ static u64 kvm_pmu_get_sample_period(struct kvm_pmc *pmc)
 	u64 sample_period;
 
 	if (!pmc->counter_val)
-		sample_period = counter_val_mask + 1;
+		sample_period = counter_val_mask;
 	else
 		sample_period = (-pmc->counter_val) & counter_val_mask;
 
-- 
2.34.1