Commit c667ad22 authored by Anup Patel's avatar Anup Patel Committed by Anup Patel
Browse files

RISC-V: KVM: Forward SBI DBCN extension to user-space 



The frozen SBI v2.0 specification defines the SBI debug console
(DBCN) extension which replaces the legacy SBI v0.1 console
functions namely sbi_console_getchar() and sbi_console_putchar().

The SBI DBCN extension needs to be emulated in the KVM user-space
(i.e. QEMU-KVM or KVMTOOL) so we forward SBI DBCN calls from KVM
guest to the KVM user-space which can then redirect the console
input/output to wherever it wants (e.g. telnet, file, stdio, etc).

The SBI debug console is simply a early console available to KVM
guest for early prints and it does not intend to replace the proper
console devices such as 8250, VirtIO console, etc.

Signed-off-by: default avatarAnup Patel <apatel@ventanamicro.com>
Reviewed-by: default avatarAndrew Jones <ajones@ventanamicro.com>
Signed-off-by: default avatarAnup Patel <anup@brainfault.org>
parent 56d8a385

arch/riscv/include/asm/kvm_vcpu_sbi.h

+1 −0
Original line number Diff line number Diff line
@@ -73,6 +73,7 @@ extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_ipi; 
extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_rfence;

extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_srst;

extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_hsm;

extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_dbcn;

extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_experimental;

extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_vendor;

arch/riscv/include/uapi/asm/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -156,6 +156,7 @@ enum KVM_RISCV_SBI_EXT_ID { 
	KVM_RISCV_SBI_EXT_PMU,

	KVM_RISCV_SBI_EXT_EXPERIMENTAL,

	KVM_RISCV_SBI_EXT_VENDOR,

	KVM_RISCV_SBI_EXT_DBCN,

	KVM_RISCV_SBI_EXT_MAX,

};

arch/riscv/kvm/vcpu_sbi.c

+4 −0
Original line number Diff line number Diff line
@@ -66,6 +66,10 @@ static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = { 
		.ext_idx = KVM_RISCV_SBI_EXT_PMU,

		.ext_ptr = &vcpu_sbi_ext_pmu,

	},

	{

		.ext_idx = KVM_RISCV_SBI_EXT_DBCN,

		.ext_ptr = &vcpu_sbi_ext_dbcn,

	},

	{

		.ext_idx = KVM_RISCV_SBI_EXT_EXPERIMENTAL,

		.ext_ptr = &vcpu_sbi_ext_experimental,

arch/riscv/kvm/vcpu_sbi_replace.c

+32 −0
Original line number Diff line number Diff line
@@ -175,3 +175,35 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_srst = { 
	.extid_end = SBI_EXT_SRST,

	.handler = kvm_sbi_ext_srst_handler,

};



static int kvm_sbi_ext_dbcn_handler(struct kvm_vcpu *vcpu,

				    struct kvm_run *run,

				    struct kvm_vcpu_sbi_return *retdata)

{

	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;

	unsigned long funcid = cp->a6;



	switch (funcid) {

	case SBI_EXT_DBCN_CONSOLE_WRITE:

	case SBI_EXT_DBCN_CONSOLE_READ:

	case SBI_EXT_DBCN_CONSOLE_WRITE_BYTE:

		/*

		 * The SBI debug console functions are unconditionally

		 * forwarded to the userspace.

		 */

		kvm_riscv_vcpu_sbi_forward(vcpu, run);

		retdata->uexit = true;

		break;

	default:

		retdata->err_val = SBI_ERR_NOT_SUPPORTED;

	}



	return 0;

}



const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_dbcn = {

	.extid_start = SBI_EXT_DBCN,

	.extid_end = SBI_EXT_DBCN,

	.default_unavail = true,

	.handler = kvm_sbi_ext_dbcn_handler,

};