[PATCH v3 1/2] RISC-V: KVM: add KVM_CAP_RISCV_MP_STATE_RESET
Radim Krčmář
rkrcmar at ventanamicro.com
Thu May 15 07:37:25 PDT 2025
Add a toggleable VM capability to reset the VCPU from userspace by
setting MP_STATE_INIT_RECEIVED through IOCTL.
Reset through a mp_state to avoid adding a new IOCTL.
Do not reset on a transition from STOPPED to RUNNABLE, because it's
better to avoid side effects that would complicate userspace adoption.
The MP_STATE_INIT_RECEIVED is not a permanent mp_state -- IOCTL resets
the VCPU while preserving the original mp_state -- because we wouldn't
gain much from having a new state it in the rest of KVM, but it's a very
non-standard use of the IOCTL.
Signed-off-by: Radim Krčmář <rkrcmar at ventanamicro.com>
---
If we want a permanent mp_state, I think that MP_STATE_UNINITIALIZED
would be reasonable. KVM could reset on transition to any other state.
v3: do not allow allow userspace to set the HSM reset state [Anup]
v2: new
---
Documentation/virt/kvm/api.rst | 11 +++++++++++
arch/riscv/include/asm/kvm_host.h | 3 +++
arch/riscv/include/asm/kvm_vcpu_sbi.h | 1 +
arch/riscv/kvm/vcpu.c | 27 ++++++++++++++-------------
arch/riscv/kvm/vcpu_sbi.c | 17 +++++++++++++++++
arch/riscv/kvm/vm.c | 13 +++++++++++++
include/uapi/linux/kvm.h | 1 +
7 files changed, 60 insertions(+), 13 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 47c7c3f92314..e107694fb41f 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8496,6 +8496,17 @@ aforementioned registers before the first KVM_RUN. These registers are VM
scoped, meaning that the same set of values are presented on all vCPUs in a
given VM.
+7.43 KVM_CAP_RISCV_MP_STATE_RESET
+---------------------------------
+
+:Architectures: riscv
+:Type: VM
+:Parameters: None
+:Returns: 0 on success, -EINVAL if arg[0] is not zero
+
+When this capability is enabled, KVM resets the VCPU when setting
+MP_STATE_INIT_RECEIVED through IOCTL. The original MP_STATE is preserved.
+
8. Other capabilities.
======================
diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index f673ebfdadf3..85cfebc32e4c 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -119,6 +119,9 @@ struct kvm_arch {
/* AIA Guest/VM context */
struct kvm_aia aia;
+
+ /* KVM_CAP_RISCV_MP_STATE_RESET */
+ bool mp_state_reset;
};
struct kvm_cpu_trap {
diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
index da28235939d1..439ab2b3534f 100644
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -57,6 +57,7 @@ void kvm_riscv_vcpu_sbi_system_reset(struct kvm_vcpu *vcpu,
u32 type, u64 flags);
void kvm_riscv_vcpu_sbi_request_reset(struct kvm_vcpu *vcpu,
unsigned long pc, unsigned long a1);
+void kvm_riscv_vcpu_sbi_load_reset_state(struct kvm_vcpu *vcpu);
int kvm_riscv_vcpu_sbi_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_riscv_vcpu_set_reg_sbi_ext(struct kvm_vcpu *vcpu,
const struct kvm_one_reg *reg);
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index a78f9ec2fa0e..521cd41bfffa 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -51,11 +51,11 @@ const struct kvm_stats_header kvm_vcpu_stats_header = {
sizeof(kvm_vcpu_stats_desc),
};
-static void kvm_riscv_vcpu_context_reset(struct kvm_vcpu *vcpu)
+static void kvm_riscv_vcpu_context_reset(struct kvm_vcpu *vcpu,
+ bool kvm_sbi_reset)
{
struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
struct kvm_cpu_context *cntx = &vcpu->arch.guest_context;
- struct kvm_vcpu_reset_state *reset_state = &vcpu->arch.reset_state;
void *vector_datap = cntx->vector.datap;
memset(cntx, 0, sizeof(*cntx));
@@ -65,13 +65,8 @@ static void kvm_riscv_vcpu_context_reset(struct kvm_vcpu *vcpu)
/* Restore datap as it's not a part of the guest context. */
cntx->vector.datap = vector_datap;
- /* Load SBI reset values */
- cntx->a0 = vcpu->vcpu_id;
-
- spin_lock(&reset_state->lock);
- cntx->sepc = reset_state->pc;
- cntx->a1 = reset_state->a1;
- spin_unlock(&reset_state->lock);
+ if (kvm_sbi_reset)
+ kvm_riscv_vcpu_sbi_load_reset_state(vcpu);
/* Setup reset state of shadow SSTATUS and HSTATUS CSRs */
cntx->sstatus = SR_SPP | SR_SPIE;
@@ -84,7 +79,7 @@ static void kvm_riscv_vcpu_context_reset(struct kvm_vcpu *vcpu)
csr->scounteren = 0x7;
}
-static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
+static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu, bool kvm_sbi_reset)
{
bool loaded;
@@ -100,7 +95,7 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
vcpu->arch.last_exit_cpu = -1;
- kvm_riscv_vcpu_context_reset(vcpu);
+ kvm_riscv_vcpu_context_reset(vcpu, kvm_sbi_reset);
kvm_riscv_vcpu_fp_reset(vcpu);
@@ -177,7 +172,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
kvm_riscv_vcpu_sbi_init(vcpu);
/* Reset VCPU */
- kvm_riscv_reset_vcpu(vcpu);
+ kvm_riscv_reset_vcpu(vcpu, false);
return 0;
}
@@ -526,6 +521,12 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
case KVM_MP_STATE_STOPPED:
__kvm_riscv_vcpu_power_off(vcpu);
break;
+ case KVM_MP_STATE_INIT_RECEIVED:
+ if (vcpu->kvm->arch.mp_state_reset)
+ kvm_riscv_reset_vcpu(vcpu, false);
+ else
+ ret = -EINVAL;
+ break;
default:
ret = -EINVAL;
}
@@ -714,7 +715,7 @@ static void kvm_riscv_check_vcpu_requests(struct kvm_vcpu *vcpu)
}
if (kvm_check_request(KVM_REQ_VCPU_RESET, vcpu))
- kvm_riscv_reset_vcpu(vcpu);
+ kvm_riscv_reset_vcpu(vcpu, true);
if (kvm_check_request(KVM_REQ_UPDATE_HGATP, vcpu))
kvm_riscv_gstage_update_hgatp(vcpu);
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index 0afef0bb261d..31fd3cc98d66 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -167,6 +167,23 @@ void kvm_riscv_vcpu_sbi_request_reset(struct kvm_vcpu *vcpu,
kvm_make_request(KVM_REQ_VCPU_RESET, vcpu);
}
+void kvm_riscv_vcpu_sbi_load_reset_state(struct kvm_vcpu *vcpu)
+{
+ struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
+ struct kvm_cpu_context *cntx = &vcpu->arch.guest_context;
+ struct kvm_vcpu_reset_state *reset_state = &vcpu->arch.reset_state;
+
+ cntx->a0 = vcpu->vcpu_id;
+
+ spin_lock(&vcpu->arch.reset_state.lock);
+ cntx->sepc = reset_state->pc;
+ cntx->a1 = reset_state->a1;
+ spin_unlock(&vcpu->arch.reset_state.lock);
+
+ cntx->sstatus &= ~SR_SIE;
+ csr->vsatp = 0;
+}
+
int kvm_riscv_vcpu_sbi_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
index 7396b8654f45..b27ec8f96697 100644
--- a/arch/riscv/kvm/vm.c
+++ b/arch/riscv/kvm/vm.c
@@ -209,6 +209,19 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
return r;
}
+int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
+{
+ switch (cap->cap) {
+ case KVM_CAP_RISCV_MP_STATE_RESET:
+ if (cap->flags)
+ return -EINVAL;
+ kvm->arch.mp_state_reset = true;
+ return 0;
+ default:
+ return -EINVAL;
+ }
+}
+
int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
{
return -EINVAL;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index b6ae8ad8934b..454b7d4a0448 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -930,6 +930,7 @@ struct kvm_enable_cap {
#define KVM_CAP_X86_APIC_BUS_CYCLES_NS 237
#define KVM_CAP_X86_GUEST_MODE 238
#define KVM_CAP_ARM_WRITABLE_IMP_ID_REGS 239
+#define KVM_CAP_RISCV_MP_STATE_RESET 240
struct kvm_irq_routing_irqchip {
__u32 irqchip;
--
2.49.0
More information about the kvm-riscv
mailing list