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RISC-V: KVM: Handle WFI exits for VCPU

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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>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
This commit is contained in:
Anup Patel 2021-09-27 17:10:07 +05:30 committed by Anup Patel
parent 9f70132651
commit 5a5d79acd7
1 changed files with 76 additions and 0 deletions
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76
arch/riscv/kvm/vcpu_exit.c
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@ -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: