Commit 5b9db9c1 authored by Radim Krčmář's avatar Radim Krčmář Committed by Anup Patel
Browse files

RISC-V: KVM: add KVM_CAP_RISCV_MP_STATE_RESET 



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: default avatarRadim Krčmář <rkrcmar@ventanamicro.com>
Reviewed-by: default avatarAnup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20250515143723.2450630-5-rkrcmar@ventanamicro.com


Signed-off-by: default avatarAnup Patel <anup@brainfault.org>
parent 5bc40978

Documentation/virt/kvm/api.rst

+11 −0
Original line number Diff line number Diff line
@@ -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.

======================

arch/riscv/include/asm/kvm_host.h

+3 −0
Original line number Diff line number Diff line
@@ -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 {

arch/riscv/include/asm/kvm_vcpu_sbi.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

arch/riscv/kvm/vcpu.c

+14 −13
Original line number Diff line number Diff line
@@ -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;
@@ -81,7 +76,7 @@ static void kvm_riscv_vcpu_context_reset(struct kvm_vcpu *vcpu) 
	cntx->hstatus |= HSTATUS_SPV;

}



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;
@@ -97,7 +92,7 @@ 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);
@@ -174,7 +169,7 @@ 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;

}
@@ -523,6 +518,12 @@ 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;

	}
@@ -711,7 +712,7 @@ 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);

arch/riscv/kvm/vcpu_sbi.c

+17 −0
Original line number Diff line number Diff line
@@ -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;