linux-kernel - [PATCH v3 09/14] RISC-V: KVM: Make PMU functionality depend on Sscofpmf

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Date:   Fri, 27 Jan 2023 10:25:53 -0800
From:   Atish Patra <atishp@...osinc.com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atishp@...osinc.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Guo Ren <guoren@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
        kvm-riscv@...ts.infradead.org, kvm@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Sergey Matyukevich <sergey.matyukevich@...tacore.com>,
        Will Deacon <will@...nel.org>
Subject: [PATCH v3 09/14] RISC-V: KVM: Make PMU functionality depend on Sscofpmf

The privilege mode filtering feature must be available in the host so
that the host can inhibit the counters while the execution is in HS mode.
Otherwise, the guests may have access to critical guest information.

Signed-off-by: Atish Patra <atishp@...osinc.com>
---
 arch/riscv/kvm/vcpu_pmu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index d3fd551..7713927 100644
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -79,6 +79,14 @@ int kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
 	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
 	struct kvm_pmc *pmc;
 
+	/*
+	 * PMU functionality should be only available to guests if privilege mode
+	 * filtering is available in the host. Otherwise, guest will always count
+	 * events while the execution is in hypervisor mode.
+	 */
+	if (!riscv_isa_extension_available(NULL, SSCOFPMF))
+		return 0;
+
 	ret = riscv_pmu_get_hpm_info(&hpm_width, &num_hw_ctrs);
 	if (ret < 0)
 		return ret;
-- 
2.25.1