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

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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: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Anup Patel 2022-07-22 19:46:24 +05:30 committed by Anup Patel
parent 56d8a385b6
commit c667ad229d
4 changed files with 38 additions and 0 deletions
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1
arch/riscv/include/asm/kvm_vcpu_sbi.h
View file

@ -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;

1
arch/riscv/include/uapi/asm/kvm.h
View file

@ -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,
};

4
arch/riscv/kvm/vcpu_sbi.c
View file

@ -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,

32
arch/riscv/kvm/vcpu_sbi_replace.c
View file

@ -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,
};