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SubjectRe: [PATCH v7 11/21] RISC-V: KVM: Handle WFI exits for VCPU
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On 04.09.19 18:15, Anup Patel wrote:
> We get illegal instruction trap whenever Guest/VM executes WFI
> instruction.
>
> This patch handles WFI trap by blocking the trapped VCPU using
> kvm_vcpu_block() API. The blocked VCPU will be automatically
> resumed whenever a VCPU interrupt is injected from user-space
> or from in-kernel IRQCHIP emulation.
>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/riscv/kvm/vcpu_exit.c | 72 ++++++++++++++++++++++++++++++++++++++
> 1 file changed, 72 insertions(+)
>
> diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
> index d75a6c35b6c7..39469f67b241 100644
> --- a/arch/riscv/kvm/vcpu_exit.c
> +++ b/arch/riscv/kvm/vcpu_exit.c
> @@ -12,6 +12,13 @@
> #include <linux/kvm_host.h>
> #include <asm/csr.h>
>
> +#define INSN_OPCODE_MASK 0x007c
> +#define INSN_OPCODE_SHIFT 2
> +#define INSN_OPCODE_SYSTEM 28
> +
> +#define INSN_MASK_WFI 0xffffff00
> +#define INSN_MATCH_WFI 0x10500000
> +
> #define INSN_MATCH_LB 0x3
> #define INSN_MASK_LB 0x707f
> #define INSN_MATCH_LH 0x1003
> @@ -112,6 +119,67 @@
> (s32)(((insn) >> 7) & 0x1f))
> #define MASK_FUNCT3 0x7000
>
> +static int truly_illegal_insn(struct kvm_vcpu *vcpu,
> + struct kvm_run *run,
> + ulong insn)
> +{
> + /* Redirect trap to Guest VCPU */
> + kvm_riscv_vcpu_trap_redirect(vcpu, EXC_INST_ILLEGAL, insn);
> +
> + return 1;
> +}
> +
> +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++;
> + if (!kvm_arch_vcpu_runnable(vcpu)) {
> + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
> + kvm_vcpu_block(vcpu);
> + vcpu->arch.srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_clear_request(KVM_REQ_UNHALT, vcpu);
> + }
> + vcpu->arch.guest_context.sepc += INSN_LEN(insn);
> + return 1;
> + }
> +
> + return truly_illegal_insn(vcpu, run, insn);
> +}
> +
> +static int illegal_inst_fault(struct kvm_vcpu *vcpu, struct kvm_run *run,
> + unsigned long insn)
> +{
> + unsigned long ut_scause = 0;
> + struct kvm_cpu_context *ct;
> +
> + if (unlikely((insn & 3) != 3)) {

What do the low 2 bits mean here? Maybe you can use a define instead?


Alex




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