On Fri, Jun 10, 2022 at 10:35:54AM +0530, Anup Patel wrote:
> Date: Fri, 10 Jun 2022 10:35:54 +0530
> From: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> Subject: [PATCH 2/3] RISC-V: KVM: Add extensible system instruction
> emulation framework
> X-Mailer: git-send-email 2.34.1
>
> We will be emulating more system instructions in near future with
> upcoming AIA, PMU, Nested and other virtualization features.
>
> To accommodate above, we add an extensible system instruction emulation
> framework in vcpu_insn.c.
>
> Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> ---
> arch/riscv/include/asm/kvm_vcpu_insn.h | 9 +++
> arch/riscv/kvm/vcpu_insn.c | 82 +++++++++++++++++++++++---
> 2 files changed, 82 insertions(+), 9 deletions(-)
>
> diff --git a/arch/riscv/include/asm/kvm_vcpu_insn.h b/arch/riscv/include/asm/kvm_vcpu_insn.h
> index 4e3ba4e84d0f..3351eb61a251 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_insn.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_insn.h
> @@ -18,6 +18,15 @@ struct kvm_mmio_decode {
> int return_handled;
> };
>
> +/* Return values used by function emulating a particular instruction */
> +enum kvm_insn_return {
> + KVM_INSN_EXIT_TO_USER_SPACE = 0,
> + KVM_INSN_CONTINUE_NEXT_SEPC,
> + KVM_INSN_CONTINUE_SAME_SEPC,
> + KVM_INSN_ILLEGAL_TRAP,
> + KVM_INSN_VIRTUAL_TRAP
> +};
> +
> void kvm_riscv_vcpu_wfi(struct kvm_vcpu *vcpu);
> int kvm_riscv_vcpu_virtual_insn(struct kvm_vcpu *vcpu, struct kvm_run *run,
> struct kvm_cpu_trap *trap);
> diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c
> index be756879c2ee..75ca62a7fba5 100644
> --- a/arch/riscv/kvm/vcpu_insn.c
> +++ b/arch/riscv/kvm/vcpu_insn.c
> @@ -118,8 +118,24 @@
> (s32)(((insn) >> 7) & 0x1f))
> #define MASK_FUNCT3 0x7000
>
> -static int truly_illegal_insn(struct kvm_vcpu *vcpu,
> - struct kvm_run *run,
> +struct insn_func {
> + unsigned long mask;
> + unsigned long match;
> + /*
> + * Possible return values are as follows:
> + * 1) Returns < 0 for error case
> + * 2) Returns 0 for exit to user-space
> + * 3) Returns 1 to continue with next sepc
> + * 4) Returns 2 to continue with same sepc
> + * 5) Returns 3 to inject illegal instruction trap and continue
> + * 6) Returns 4 to inject virtual instruction trap and continue
> + *
> + * Use enum kvm_insn_return for return values
> + */
> + int (*func)(struct kvm_vcpu *vcpu, struct kvm_run *run, ulong insn);
> +};
> +
> +static int truly_illegal_insn(struct kvm_vcpu *vcpu, struct kvm_run *run,
> ulong insn)
> {
> struct kvm_cpu_trap utrap = { 0 };
> @@ -128,6 +144,24 @@ static int truly_illegal_insn(struct kvm_vcpu *vcpu,
> utrap.sepc = vcpu->arch.guest_context.sepc;
> utrap.scause = EXC_INST_ILLEGAL;
> utrap.stval = insn;
> + utrap.htval = 0;
> + utrap.htinst = 0;
> + kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);
> +
> + return 1;
> +}
> +
> +static int truly_virtual_insn(struct kvm_vcpu *vcpu, struct kvm_run *run,
> + ulong insn)
> +{
> + struct kvm_cpu_trap utrap = { 0 };
> +
> + /* Redirect trap to Guest VCPU */
> + utrap.sepc = vcpu->arch.guest_context.sepc;
> + utrap.scause = EXC_VIRTUAL_INST_FAULT;
> + utrap.stval = insn;
> + utrap.htval = 0;
> + utrap.htinst = 0;
> kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);
>
> return 1;
> @@ -148,18 +182,48 @@ void kvm_riscv_vcpu_wfi(struct kvm_vcpu *vcpu)
> }
> }
>
> -static int system_opcode_insn(struct kvm_vcpu *vcpu,
> - struct kvm_run *run,
> +static int wfi_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, ulong insn)
> +{
> + vcpu->stat.wfi_exit_stat++;
> + kvm_riscv_vcpu_wfi(vcpu);
> + return KVM_INSN_CONTINUE_NEXT_SEPC;
> +}
> +
> +static const struct insn_func system_opcode_funcs[] = {
> + {
> + .mask = INSN_MASK_WFI,
> + .match = INSN_MATCH_WFI,
> + .func = wfi_insn,
> + },
> +};
> +
> +static int system_opcode_insn(struct kvm_vcpu *vcpu, struct kvm_run *run,
> ulong insn)
> {
> - if ((insn & INSN_MASK_WFI) == INSN_MATCH_WFI) {
> - vcpu->stat.wfi_exit_stat++;
> - kvm_riscv_vcpu_wfi(vcpu);
> + int i, rc = KVM_INSN_ILLEGAL_TRAP;
> + const struct insn_func *ifn;
> +
> + for (i = 0; i < ARRAY_SIZE(system_opcode_funcs); i++) {
> + ifn = &system_opcode_funcs[i];
> + if ((insn & ifn->mask) == ifn->match) {
> + rc = ifn->func(vcpu, run, insn);
> + break;
> + }
> + }
> +
> + switch (rc) {
> + case KVM_INSN_ILLEGAL_TRAP:
> + return truly_illegal_insn(vcpu, run, insn);
> + case KVM_INSN_VIRTUAL_TRAP:
> + return truly_virtual_insn(vcpu, run, insn);
> + case KVM_INSN_CONTINUE_NEXT_SEPC:
> vcpu->arch.guest_context.sepc += INSN_LEN(insn);
> - return 1;
> + break;
Hi Anup,
What about adding KVM_INSN_CONTINUE_SAME_SEPC and KVM_INSN_EXIT_TO_USER_SPACE
cases here and set rc to 1?
This is the explicit indication that both cases are handled.
> + default:
> + break;
> }
>
> - return truly_illegal_insn(vcpu, run, insn);
> + return (rc <= 0) ? rc : 1;
> }
>
> /**
> --
> 2.34.1
>
>
> --
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