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@brainfault.org>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index dc3c118efb5782615ae47445b1cfab162087a998..921340413846c15b2d8b3dfe665abfb4fbfa7bcb 100644 (file)
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -80,6 +80,14 @@ 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;