linux-kernel - [PATCH v6 10/24] RISC-V: KVM: Fix the initial sample period value

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Message-Id: <20240411000752.955910-11-atishp@rivosinc.com>
Date: Wed, 10 Apr 2024 17:07:38 -0700
From: Atish Patra <atishp@...osinc.com>
To: linux-kernel@...r.kernel.org
Cc: Atish Patra <atishp@...osinc.com>,
	Andrew Jones <ajones@...tanamicro.com>,
	Ajay Kaher <ajay.kaher@...adcom.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Alexey Makhalov <alexey.amakhalov@...adcom.com>,
	Anup Patel <anup@...infault.org>,
	Atish Patra <atishp@...shpatra.org>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	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,
	Will Deacon <will@...nel.org>,
	x86@...nel.org
Subject: [PATCH v6 10/24] 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.

Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
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