[PATCH v3 5/6] KVM: riscv: Support guest wrs.nto

[Anup Patel]

On Fri, Apr 26, 2024 at 3:38 PM Andrew Jones <ajones at ventanamicro.com> wrote:
>
> When a guest traps on wrs.nto, call kvm_vcpu_on_spin() to attempt
> to yield to the lock holding VCPU. Also extend the KVM ISA extension
> ONE_REG interface to allow KVM userspace to detect and enable the
> Zawrs extension for the Guest/VM.
>
> Signed-off-by: Andrew Jones <ajones at ventanamicro.com>

LGTM.

Acked-by: Anup Patel <anup at brainfault.org>

Regards,
Anup

> ---
>  arch/riscv/include/asm/kvm_host.h |  1 +
>  arch/riscv/include/uapi/asm/kvm.h |  1 +
>  arch/riscv/kvm/vcpu.c             |  1 +
>  arch/riscv/kvm/vcpu_insn.c        | 15 +++++++++++++++
>  arch/riscv/kvm/vcpu_onereg.c      |  2 ++
>  5 files changed, 20 insertions(+)
>
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index 484d04a92fa6..e27c56e44783 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -69,6 +69,7 @@ struct kvm_vcpu_stat {
>         struct kvm_vcpu_stat_generic generic;
>         u64 ecall_exit_stat;
>         u64 wfi_exit_stat;
> +       u64 wrs_exit_stat;
>         u64 mmio_exit_user;
>         u64 mmio_exit_kernel;
>         u64 csr_exit_user;
> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> index b1c503c2959c..89ea06bd07c2 100644
> --- a/arch/riscv/include/uapi/asm/kvm.h
> +++ b/arch/riscv/include/uapi/asm/kvm.h
> @@ -167,6 +167,7 @@ enum KVM_RISCV_ISA_EXT_ID {
>         KVM_RISCV_ISA_EXT_ZFA,
>         KVM_RISCV_ISA_EXT_ZTSO,
>         KVM_RISCV_ISA_EXT_ZACAS,
> +       KVM_RISCV_ISA_EXT_ZAWRS,
>         KVM_RISCV_ISA_EXT_MAX,
>  };
>
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index b5ca9f2e98ac..abcdc78671e0 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -25,6 +25,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
>         KVM_GENERIC_VCPU_STATS(),
>         STATS_DESC_COUNTER(VCPU, ecall_exit_stat),
>         STATS_DESC_COUNTER(VCPU, wfi_exit_stat),
> +       STATS_DESC_COUNTER(VCPU, wrs_exit_stat),
>         STATS_DESC_COUNTER(VCPU, mmio_exit_user),
>         STATS_DESC_COUNTER(VCPU, mmio_exit_kernel),
>         STATS_DESC_COUNTER(VCPU, csr_exit_user),
> diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c
> index ee7215f4071f..97dec18e6989 100644
> --- a/arch/riscv/kvm/vcpu_insn.c
> +++ b/arch/riscv/kvm/vcpu_insn.c
> @@ -16,6 +16,9 @@
>  #define INSN_MASK_WFI          0xffffffff
>  #define INSN_MATCH_WFI         0x10500073
>
> +#define INSN_MASK_WRS          0xffffffff
> +#define INSN_MATCH_WRS         0x00d00073
> +
>  #define INSN_MATCH_CSRRW       0x1073
>  #define INSN_MASK_CSRRW                0x707f
>  #define INSN_MATCH_CSRRS       0x2073
> @@ -203,6 +206,13 @@ static int wfi_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, ulong insn)
>         return KVM_INSN_CONTINUE_NEXT_SEPC;
>  }
>
> +static int wrs_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, ulong insn)
> +{
> +       vcpu->stat.wrs_exit_stat++;
> +       kvm_vcpu_on_spin(vcpu, vcpu->arch.guest_context.sstatus & SR_SPP);
> +       return KVM_INSN_CONTINUE_NEXT_SEPC;
> +}
> +
>  struct csr_func {
>         unsigned int base;
>         unsigned int count;
> @@ -378,6 +388,11 @@ static const struct insn_func system_opcode_funcs[] = {
>                 .match = INSN_MATCH_WFI,
>                 .func  = wfi_insn,
>         },
> +       {
> +               .mask  = INSN_MASK_WRS,
> +               .match = INSN_MATCH_WRS,
> +               .func  = wrs_insn,
> +       },
>  };
>
>  static int system_opcode_insn(struct kvm_vcpu *vcpu, struct kvm_run *run,
> diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
> index f4a6124d25c9..67c5794af3b6 100644
> --- a/arch/riscv/kvm/vcpu_onereg.c
> +++ b/arch/riscv/kvm/vcpu_onereg.c
> @@ -41,6 +41,7 @@ static const unsigned long kvm_isa_ext_arr[] = {
>         KVM_ISA_EXT_ARR(SVNAPOT),
>         KVM_ISA_EXT_ARR(SVPBMT),
>         KVM_ISA_EXT_ARR(ZACAS),
> +       KVM_ISA_EXT_ARR(ZAWRS),
>         KVM_ISA_EXT_ARR(ZBA),
>         KVM_ISA_EXT_ARR(ZBB),
>         KVM_ISA_EXT_ARR(ZBC),
> @@ -120,6 +121,7 @@ static bool kvm_riscv_vcpu_isa_disable_allowed(unsigned long ext)
>         case KVM_RISCV_ISA_EXT_SVINVAL:
>         case KVM_RISCV_ISA_EXT_SVNAPOT:
>         case KVM_RISCV_ISA_EXT_ZACAS:
> +       case KVM_RISCV_ISA_EXT_ZAWRS:
>         case KVM_RISCV_ISA_EXT_ZBA:
>         case KVM_RISCV_ISA_EXT_ZBB:
>         case KVM_RISCV_ISA_EXT_ZBC:
> --
> 2.44.0
>