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SubjectRe: [PATCH v2 08/11] RISC-V: KVM: Disable all hpmcounter access for VS/VU mode
On Thu, Dec 15, 2022 at 09:00:43AM -0800, Atish Patra wrote:
> Any guest must not get access to any hpmcounter including cycle/instret
> without any checks. We achieve that by disabling all the bits except TM
> bit in hcountern.

hcounteren

>
> However, instret and cycle access for guest userspace can be enabled
> upon explicit request (via ONE REG) or on first trap from VU mode
> to maintain ABI requirement in the future. This patch doesn't support
> that as ONE REG inteface is not settled yet.
>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---
> arch/riscv/kvm/main.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
> index 58c5489..9c2efd3 100644
> --- a/arch/riscv/kvm/main.c
> +++ b/arch/riscv/kvm/main.c
> @@ -49,7 +49,8 @@ int kvm_arch_hardware_enable(void)
> hideleg |= (1UL << IRQ_VS_EXT);
> csr_write(CSR_HIDELEG, hideleg);
>
> - csr_write(CSR_HCOUNTEREN, -1UL);
> + /* VS should access only TM bit. Everything else should trap */

s/TM bit/the time counter/

> + csr_write(CSR_HCOUNTEREN, 0x02);
>
> csr_write(CSR_HVIP, 0);
>
> --
> 2.25.1
>

Otherwise,

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

Thanks,
drew

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