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From:   Anup Patel <Anup.Patel@wdc.com>
To:     Palmer Dabbelt <palmer@sifive.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim K <rkrcmar@redhat.com>
CC:     Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Atish Patra <Atish.Patra@wdc.com>,
        Alistair Francis <Alistair.Francis@wdc.com>,
        Damien Le Moal <Damien.LeMoal@wdc.com>,
        Christoph Hellwig <hch@infradead.org>,
        Anup Patel <anup@brainfault.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Anup Patel <Anup.Patel@wdc.com>
Subject: [PATCH v6 11/21] RISC-V: KVM: Handle WFI exits for VCPU
Thread-Topic: [PATCH v6 11/21] RISC-V: KVM: Handle WFI exits for VCPU
Thread-Index: AQHVXnGLmMAkHOr9W0O2flFRXn5nSA==
Date:   Thu, 29 Aug 2019 13:56:24 +0000
Message-ID: <20190829135427.47808-12-anup.patel@wdc.com>
References: <20190829135427.47808-1-anup.patel@wdc.com>
In-Reply-To: <20190829135427.47808-1-anup.patel@wdc.com>
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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>
---
 arch/riscv/kvm/vcpu_exit.c | 71 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
index 700d8158e55b..321062fff65b 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>
=20
+#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 +119,66 @@
 				 (s32)(((insn) >> 7) & 0x1f))
 #define MASK_FUNCT3		0x7000
=20
+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) =3D=3D 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 =3D srcu_read_lock(&vcpu->kvm->srcu);
+			kvm_clear_request(KVM_REQ_UNHALT, vcpu);
+		}
+		vcpu->arch.guest_context.sepc +=3D 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 =3D 0, ut_stval =3D 0;
+	struct kvm_cpu_context *ct;
+
+	if (unlikely((insn & 3) !=3D 3)) {
+		if (insn =3D=3D 0) {
+			ct =3D &vcpu->arch.guest_context;
+			insn =3D kvm_riscv_vcpu_unpriv_read(vcpu, true,
+							  ct->sepc,
+							  &ut_scause,
+							  &ut_stval);
+			if (ut_scause) {
+				kvm_riscv_vcpu_trap_redirect(vcpu, ut_scause,
+							     ut_stval);
+				return 1;
+			}
+		}
+		if ((insn & 3) !=3D 3)
+			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)
 {
@@ -507,6 +574,10 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct =
kvm_run *run,
 	ret =3D -EFAULT;
 	run->exit_reason =3D KVM_EXIT_UNKNOWN;
 	switch (scause) {
+	case EXC_INST_ILLEGAL:
+		if (vcpu->arch.guest_context.hstatus & HSTATUS_SPV)
+			ret =3D illegal_inst_fault(vcpu, run, stval);
+		break;
 	case EXC_INST_PAGE_FAULT:
 	case EXC_LOAD_PAGE_FAULT:
 	case EXC_STORE_PAGE_FAULT:
--=20
2.17.1