From: SeungJu Cheon <suunj1331@gmail.com>
To: Anup Patel <anup@brainfault.org>, Atish Patra <atish.patra@linux.dev>
Cc: Paul Walmsley <pjw@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>,
Andrew Jones <ajones@ventanamicro.com>,
kvm@vger.kernel.org, kvm-riscv@lists.infradead.org,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
Shuah Khan <skhan@linuxfoundation.org>,
linux-kernel-mentees@lists.linux.dev, me@brighamcampbell.com,
SeungJu Cheon <suunj1331@gmail.com>
Subject: [PATCH v1 2/3] RISC-V: KVM: Report snapshot write failure to the guest
Date: Tue, 25 Aug 2026 17:37:18 +0900 [thread overview]
Message-ID: <20260825083719.643970-3-suunj1331@gmail.com> (raw)
In-Reply-To: <20260825083719.643970-1-suunj1331@gmail.com>
If kvm_vcpu_write_guest() fails while updating the PMU snapshot area
on counter stop, the guest may receive SBI_SUCCESS without the
snapshot being updated, leaving stale data in shared memory.
Return SBI_ERR_FAILURE when the snapshot write fails.
Fixes: c2f41ddbcdd7 ("RISC-V: KVM: Implement SBI PMU Snapshot feature")
Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>
---
arch/riscv/kvm/vcpu_pmu.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index 56dd5b1b2846..45dd5233340d 100644
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -723,9 +723,10 @@ int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base,
}
}
- if (shmem_needs_update)
- kvm_vcpu_write_guest(vcpu, kvpmu->snapshot_addr, kvpmu->sdata,
- sizeof(struct riscv_pmu_snapshot_data));
+ if (shmem_needs_update &&
+ kvm_vcpu_write_guest(vcpu, kvpmu->snapshot_addr, kvpmu->sdata,
+ sizeof(struct riscv_pmu_snapshot_data)))
+ sbiret = SBI_ERR_FAILURE;
out:
retdata->err_val = sbiret;
--
2.52.0
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next prev parent reply other threads:[~2026-08-25 8:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-25 8:37 [PATCH v1 0/3] RISC-V: KVM: Fix PMU counter handling issues SeungJu Cheon
2026-08-25 8:37 ` [PATCH v1 1/3] RISC-V: KVM: Preserve firmware counter value across stop/start SeungJu Cheon
2026-08-25 8:37 ` SeungJu Cheon [this message]
2026-08-25 8:37 ` [PATCH v1 3/3] RISC-V: KVM: Fix perf-backed counter accounting across stop and read SeungJu Cheon
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