RISC-V: KVM: Add SBI system suspend support

Implement a KVM SBI SUSP extension handler. The handler only
validates the system suspend entry criteria and prepares for resuming
in the appropriate state at the resume_addr (as specified by the SBI
spec), but then it forwards the call to the VMM where any system
suspend behavior may be implemented. Since VMM support is needed, KVM
disables the extension by default.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20241017074538.18867-5-ajones@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>

3 files changed, 78 insertions, 0 deletions

diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
index 0fb1840c3e0a..4e0bba91d284 100644
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile
@@ -30,6 +30,7 @@ kvm-y += vcpu_sbi_hsm.o
 kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_sbi_pmu.o
 kvm-y += vcpu_sbi_replace.o
 kvm-y += vcpu_sbi_sta.o
+kvm-y += vcpu_sbi_system.o
 kvm-$(CONFIG_RISCV_SBI_V01) += vcpu_sbi_v01.o
 kvm-y += vcpu_switch.o
 kvm-y += vcpu_timer.o
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index 6e704ed86a83..d1c83a77735e 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -71,6 +71,10 @@ static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = {
 		.ext_ptr = &vcpu_sbi_ext_dbcn,
 	},
 	{
+		.ext_idx = KVM_RISCV_SBI_EXT_SUSP,
+		.ext_ptr = &vcpu_sbi_ext_susp,
+	},
+	{
 		.ext_idx = KVM_RISCV_SBI_EXT_STA,
 		.ext_ptr = &vcpu_sbi_ext_sta,
 	},
diff --git a/arch/riscv/kvm/vcpu_sbi_system.c b/arch/riscv/kvm/vcpu_sbi_system.c
new file mode 100644
index 000000000000..5d55e08791fa
--- /dev/null
+++ b/arch/riscv/kvm/vcpu_sbi_system.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2024 Ventana Micro Systems Inc.
+ */
+
+#include <linux/kvm_host.h>
+
+#include <asm/kvm_vcpu_sbi.h>
+#include <asm/sbi.h>
+
+static int kvm_sbi_ext_susp_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
+				    struct kvm_vcpu_sbi_return *retdata)
+{
+	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
+	struct kvm_cpu_context *reset_cntx;
+	unsigned long funcid = cp->a6;
+	unsigned long hva, i;
+	struct kvm_vcpu *tmp;
+
+	switch (funcid) {
+	case SBI_EXT_SUSP_SYSTEM_SUSPEND:
+		if (cp->a0 != SBI_SUSP_SLEEP_TYPE_SUSPEND_TO_RAM) {
+			retdata->err_val = SBI_ERR_INVALID_PARAM;
+			return 0;
+		}
+
+		if (!(cp->sstatus & SR_SPP)) {
+			retdata->err_val = SBI_ERR_FAILURE;
+			return 0;
+		}
+
+		hva = kvm_vcpu_gfn_to_hva_prot(vcpu, cp->a1 >> PAGE_SHIFT, NULL);
+		if (kvm_is_error_hva(hva)) {
+			retdata->err_val = SBI_ERR_INVALID_ADDRESS;
+			return 0;
+		}
+
+		kvm_for_each_vcpu(i, tmp, vcpu->kvm) {
+			if (tmp == vcpu)
+				continue;
+			if (!kvm_riscv_vcpu_stopped(tmp)) {
+				retdata->err_val = SBI_ERR_DENIED;
+				return 0;
+			}
+		}
+
+		spin_lock(&vcpu->arch.reset_cntx_lock);
+		reset_cntx = &vcpu->arch.guest_reset_context;
+		reset_cntx->sepc = cp->a1;
+		reset_cntx->a0 = vcpu->vcpu_id;
+		reset_cntx->a1 = cp->a2;
+		spin_unlock(&vcpu->arch.reset_cntx_lock);
+
+		kvm_make_request(KVM_REQ_VCPU_RESET, vcpu);
+
+		/* userspace provides the suspend implementation */
+		kvm_riscv_vcpu_sbi_forward(vcpu, run);
+		retdata->uexit = true;
+		break;
+	default:
+		retdata->err_val = SBI_ERR_NOT_SUPPORTED;
+		break;
+	}
+
+	return 0;
+}
+
+const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_susp = {
+	.extid_start = SBI_EXT_SUSP,
+	.extid_end = SBI_EXT_SUSP,
+	.default_disabled = true,
+	.handler = kvm_sbi_ext_susp_handler,
+};