[kvmtool,05/10] riscv: Add SBI system suspend support

Commit Message

Anup Patel March 26, 2025, 6:56 a.m. UTC

From: Andrew Jones <[e-mail]>

Provide a handler for SBI system suspend requests forwarded to the
VMM by KVM and enable system suspend by default. This is just for
testing purposes, so the handler only sleeps 5 seconds before
resuming the guest. Resuming a system suspend only requires running
the system suspend invoking hart again, everything else is handled by
KVM.

Note, resuming after a suspend doesn't work with 9p used for the
guest's rootfs. Testing with a disk works though, e.g.

  lkvm-static run --nodefaults -m 256 -c 2 -d rootfs.ext2 -k Image \
    -p 'console=ttyS0 rootwait root=/dev/vda ro no_console_suspend'

Signed-off-by: Andrew Jones <[e-mail]>
Signed-off-by: Anup Patel <[e-mail]>
---
 riscv/include/kvm/kvm-config-arch.h |  3 +++
 riscv/include/kvm/sbi.h             |  9 ++++++++
 riscv/kvm-cpu.c                     | 36 +++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+)

Patch

diff --git a/riscv/include/kvm/kvm-config-arch.h b/riscv/include/kvm/kvm-config-arch.h
index 5badb74..0553004 100644
--- a/riscv/include/kvm/kvm-config-arch.h
+++ b/riscv/include/kvm/kvm-config-arch.h
@@ -238,6 +238,9 @@  struct kvm_config_arch {
 	OPT_BOOLEAN('\0', "disable-sbi-dbcn",				\
 		    &(cfg)->sbi_ext_disabled[KVM_RISCV_SBI_EXT_DBCN],	\
 		    "Disable SBI DBCN Extension"),			\
+	OPT_BOOLEAN('\0', "disable-sbi-susp",				\
+		    &(cfg)->sbi_ext_disabled[KVM_RISCV_SBI_EXT_SUSP],	\
+		    "Disable SBI SUSP Extension"),			\
 	OPT_BOOLEAN('\0', "disable-sbi-sta",				\
 		    &(cfg)->sbi_ext_disabled[KVM_RISCV_SBI_EXT_STA],	\
 		    "Disable SBI STA Extension"),
diff --git a/riscv/include/kvm/sbi.h b/riscv/include/kvm/sbi.h
index a0f2c70..10bbe1b 100644
--- a/riscv/include/kvm/sbi.h
+++ b/riscv/include/kvm/sbi.h
@@ -21,6 +21,7 @@  enum sbi_ext_id {
 	SBI_EXT_0_1_SHUTDOWN = 0x8,
 	SBI_EXT_BASE = 0x10,
 	SBI_EXT_DBCN = 0x4442434E,
+	SBI_EXT_SUSP = 0x53555350,
 };
 
 enum sbi_ext_base_fid {
@@ -39,6 +40,14 @@  enum sbi_ext_dbcn_fid {
 	SBI_EXT_DBCN_CONSOLE_WRITE_BYTE = 2,
 };
 
+enum sbi_ext_susp_fid {
+	SBI_EXT_SUSP_SYSTEM_SUSPEND = 0,
+};
+
+enum sbi_ext_susp_sleep_type {
+	SBI_SUSP_SLEEP_TYPE_SUSPEND_TO_RAM = 0,
+};
+
 #define SBI_SPEC_VERSION_DEFAULT	0x1
 #define SBI_SPEC_VERSION_MAJOR_OFFSET	24
 #define SBI_SPEC_VERSION_MAJOR_MASK	0x7f
diff --git a/riscv/kvm-cpu.c b/riscv/kvm-cpu.c
index 0c171da..ad68b58 100644
--- a/riscv/kvm-cpu.c
+++ b/riscv/kvm-cpu.c
@@ -1,3 +1,5 @@ 
+#include <unistd.h>
+
 #include "kvm/csr.h"
 #include "kvm/kvm-cpu.h"
 #include "kvm/kvm.h"
@@ -117,6 +119,17 @@  struct kvm_cpu *kvm_cpu__arch_init(struct kvm *kvm, unsigned long cpu_id)
 				   KVM_RISCV_SBI_EXT_DBCN);
 	}
 
+	/* Force enable SBI system suspend if not disabled from command line */
+	if (!kvm->cfg.arch.sbi_ext_disabled[KVM_RISCV_SBI_EXT_SUSP]) {
+		id = 1;
+		reg.id = RISCV_SBI_EXT_REG(KVM_REG_RISCV_SBI_SINGLE,
+					   KVM_RISCV_SBI_EXT_SUSP);
+		reg.addr = (unsigned long)&id;
+		if (ioctl(vcpu->vcpu_fd, KVM_SET_ONE_REG, &reg) < 0)
+			pr_warning("KVM_SET_ONE_REG failed (sbi_ext %d)",
+				   KVM_RISCV_SBI_EXT_SUSP);
+	}
+
 	/* Populate the vcpu structure. */
 	vcpu->kvm		= kvm;
 	vcpu->cpu_id		= cpu_id;
@@ -203,6 +216,29 @@  static bool kvm_cpu_riscv_sbi(struct kvm_cpu *vcpu)
 			break;
 		}
 		break;
+	case SBI_EXT_SUSP:
+	{
+		unsigned long susp_type, ret = SBI_SUCCESS;
+
+		switch (vcpu->kvm_run->riscv_sbi.function_id) {
+		case SBI_EXT_SUSP_SYSTEM_SUSPEND:
+			susp_type = vcpu->kvm_run->riscv_sbi.args[0];
+			if (susp_type != SBI_SUSP_SLEEP_TYPE_SUSPEND_TO_RAM) {
+				ret = SBI_ERR_INVALID_PARAM;
+				break;
+			}
+
+			sleep(5);
+
+			break;
+		default:
+			ret = SBI_ERR_NOT_SUPPORTED;
+			break;
+		}
+
+		vcpu->kvm_run->riscv_sbi.ret[0] = ret;
+		break;
+	}
 	default:
 		dprintf(dfd, "Unhandled SBI call\n");
 		dprintf(dfd, "extension_id=0x%lx function_id=0x%lx\n",