Commit 5a5d79ac authored by Anup Patel's avatar Anup Patel Committed by Anup Patel
Browse files

RISC-V: KVM: Handle WFI exits for VCPU 



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: default avatarAnup Patel <anup.patel@wdc.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Acked-by: default avatarPalmer Dabbelt <palmerdabbelt@google.com>
parent 9f701326

arch/riscv/kvm/vcpu_exit.c

+76 −0
Original line number Diff line number Diff line
@@ -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		0xffffffff

#define INSN_MATCH_WFI		0x10500073



#define INSN_MATCH_LB		0x3

#define INSN_MASK_LB		0x707f

#define INSN_MATCH_LH		0x1003
@@ -116,6 +123,71 @@ 
				 (s32)(((insn) >> 7) & 0x1f))

#define MASK_FUNCT3		0x7000



static int truly_illegal_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_INST_ILLEGAL;

	utrap.stval = insn;

	kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);



	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 virtual_inst_fault(struct kvm_vcpu *vcpu, struct kvm_run *run,

			      struct kvm_cpu_trap *trap)

{

	unsigned long insn = trap->stval;

	struct kvm_cpu_trap utrap = { 0 };

	struct kvm_cpu_context *ct;



	if (unlikely(INSN_IS_16BIT(insn))) {

		if (insn == 0) {

			ct = &vcpu->arch.guest_context;

			insn = kvm_riscv_vcpu_unpriv_read(vcpu, true,

							  ct->sepc,

							  &utrap);

			if (utrap.scause) {

				utrap.sepc = ct->sepc;

				kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);

				return 1;

			}

		}

		if (INSN_IS_16BIT(insn))

			return truly_illegal_insn(vcpu, run, insn);

	}



	switch ((insn & INSN_OPCODE_MASK) >> INSN_OPCODE_SHIFT) {

	case INSN_OPCODE_SYSTEM:

		return system_opcode_insn(vcpu, run, insn);

	default:

		return truly_illegal_insn(vcpu, run, insn);

	}

}



static int emulate_load(struct kvm_vcpu *vcpu, struct kvm_run *run,

			unsigned long fault_addr, unsigned long htinst)

{
@@ -596,6 +668,10 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run, 
	ret = -EFAULT;

	run->exit_reason = KVM_EXIT_UNKNOWN;

	switch (trap->scause) {

	case EXC_VIRTUAL_INST_FAULT:

		if (vcpu->arch.guest_context.hstatus & HSTATUS_SPV)

			ret = virtual_inst_fault(vcpu, run, trap);

		break;

	case EXC_INST_GUEST_PAGE_FAULT:

	case EXC_LOAD_GUEST_PAGE_FAULT:

	case EXC_STORE_GUEST_PAGE_FAULT: