On Wed, Apr 10, 2024 at 05:07:42PM -0700, Atish Patra wrote:
KVM enables perf for guest via counter virtualization. However, the sampling can not be supported as there is no mechanism to enabled trap/emulate scountovf in ISA yet. Rely on the SBI PMU snapshot to provide the counter overflow data via the shared memory.
In case of sampling event, the host first sets the guest's LCOFI interrupt and injects to the guest via irq filtering mechanism defined in AIA specification. Thus, ssaia must be enabled in the host in order to use perf sampling in the guest. No other AIA dependency w.r.t kernel is required.
Reviewed-by: Anup Patel anup@brainfault.org Signed-off-by: Atish Patra atishp@rivosinc.com
arch/riscv/include/asm/csr.h | 3 +- arch/riscv/include/asm/kvm_vcpu_pmu.h | 3 ++ arch/riscv/include/uapi/asm/kvm.h | 1 + arch/riscv/kvm/aia.c | 5 ++ arch/riscv/kvm/vcpu.c | 15 ++++-- arch/riscv/kvm/vcpu_onereg.c | 6 +++ arch/riscv/kvm/vcpu_pmu.c | 68 +++++++++++++++++++++++++-- 7 files changed, 93 insertions(+), 8 deletions(-)
Reviewed-by: Andrew Jones ajones@ventanamicro.com