linux-kernel - [PATCH v4 09/14] RISC-V: KVM: Make PMU functionality depend on Sscofpmf

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Date:   Wed,  1 Feb 2023 15:12:45 -0800
From:   Atish Patra <atishp@...osinc.com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atishp@...osinc.com>,
        Anup Patel <anup@...infault.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Jones <ajones@...tanamicro.com>,
        Atish Patra <atishp@...shpatra.org>,
        Eric Lin <eric.lin@...ive.com>, 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>,
        Will Deacon <will@...nel.org>
Subject: [PATCH v4 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.

Reviewed-by: Anup Patel <anup@...infault.org>
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 2dad37f..9a531fe 100644
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -79,6 +79,14 @@ void 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;
+
 	ret = riscv_pmu_get_hpm_info(&hpm_width, &num_hw_ctrs);
 	if (ret < 0 || !hpm_width || !num_hw_ctrs)
 		return;
-- 
2.25.1