[PATCH v5 11/20] RISC-V: KVM: Handle WFI exits for VCPU

Anup Patel
2019-08-22T08:45:13Z

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 | 88 ++++++++++++++++++++++++++++++++++++++
1 file changed, 88 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
index efc06198c259..fbc04fe335ad 100644
--- a/arch/riscv/kvm/vcpu_exit.c
+++ b/arch/riscv/kvm/vcpu_exit.c
@@ -12,6 +12,9 @@
#include <linux/kvm_host.h>
#include <asm/csr.h>

+#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
@@ -179,6 +182,87 @@ static ulong get_insn(struct kvm_vcpu *vcpu)
return val;
}

+typedef int (*illegal_insn_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)
+{
+ /* TODO: Redirect trap to Guest VCPU */
+ return -ENOTSUPP;
+}
+
+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 illegal_insn_func illegal_insn_table[32] = {
+ truly_illegal_insn, /* 0 */
+ truly_illegal_insn, /* 1 */
+ truly_illegal_insn, /* 2 */
+ truly_illegal_insn, /* 3 */
+ truly_illegal_insn, /* 4 */
+ truly_illegal_insn, /* 5 */
+ truly_illegal_insn, /* 6 */
+ truly_illegal_insn, /* 7 */
+ truly_illegal_insn, /* 8 */
+ truly_illegal_insn, /* 9 */
+ truly_illegal_insn, /* 10 */
+ truly_illegal_insn, /* 11 */
+ truly_illegal_insn, /* 12 */
+ truly_illegal_insn, /* 13 */
+ truly_illegal_insn, /* 14 */
+ truly_illegal_insn, /* 15 */
+ truly_illegal_insn, /* 16 */
+ truly_illegal_insn, /* 17 */
+ truly_illegal_insn, /* 18 */
+ truly_illegal_insn, /* 19 */
+ truly_illegal_insn, /* 20 */
+ truly_illegal_insn, /* 21 */
+ truly_illegal_insn, /* 22 */
+ truly_illegal_insn, /* 23 */
+ truly_illegal_insn, /* 24 */
+ truly_illegal_insn, /* 25 */
+ truly_illegal_insn, /* 26 */
+ truly_illegal_insn, /* 27 */
+ system_opcode_insn, /* 28 */
+ truly_illegal_insn, /* 29 */
+ truly_illegal_insn, /* 30 */
+ truly_illegal_insn /* 31 */
+};
+
+static int illegal_inst_fault(struct kvm_vcpu *vcpu, struct kvm_run *run,
+ unsigned long stval)
+{
+ ulong insn = stval;
+
+ if (unlikely((insn & 3) != 3)) {
+ if (insn == 0)
+ insn = get_insn(vcpu);
+ if ((insn & 3) != 3)
+ return truly_illegal_insn(vcpu, run, insn);
+ }
+
+ return illegal_insn_table[(insn & 0x7c) >> 2](vcpu, run, insn);
+}
+
static int emulate_load(struct kvm_vcpu *vcpu, struct kvm_run *run,
unsigned long fault_addr)
{
@@ -439,6 +523,10 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
ret = -EFAULT;
run->exit_reason = KVM_EXIT_UNKNOWN;
switch (scause) {
+ case EXC_INST_ILLEGAL:
+ if (vcpu->arch.guest_context.hstatus & HSTATUS_SPV)
+ ret = illegal_inst_fault(vcpu, run, stval);
+ break;
case EXC_INST_PAGE_FAULT:
case EXC_LOAD_PAGE_FAULT:
case EXC_STORE_PAGE_FAULT:
--
2.17.1