[PATCH 9/9] RISC-V: KVM: Add ONE_REG interface to enable/disable SBI extensions

From: Anup Patel
Date: Mon Nov 28 2022 - 11:15:49 EST

We add ONE_REG interface to enable/disable SBI extensions (just
like the ONE_REG interface for ISA extensions). This allows KVM
user-space to decide the set of SBI extension enabled for a Guest
and by default all SBI extensions are enabled.

Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
---
arch/riscv/include/asm/kvm_vcpu_sbi.h | 8 +-
arch/riscv/include/uapi/asm/kvm.h | 19 ++++
arch/riscv/kvm/vcpu.c | 2 +
arch/riscv/kvm/vcpu_sbi.c | 145 +++++++++++++++++++++++---
arch/riscv/kvm/vcpu_sbi_base.c | 2 +-
5 files changed, 158 insertions(+), 18 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
index f79478a85d2d..baa342dadf95 100644
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -16,6 +16,7 @@

struct kvm_vcpu_sbi_context {
int return_handled;
+ bool extension_disabled[KVM_RISCV_SBI_EXT_MAX];
};

struct kvm_vcpu_sbi_extension {
@@ -36,7 +37,12 @@ void kvm_riscv_vcpu_sbi_system_reset(struct kvm_vcpu *vcpu,
struct kvm_run *run,
u32 type, u64 flags);
int kvm_riscv_vcpu_sbi_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
-const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(unsigned long extid);
+int kvm_riscv_vcpu_set_reg_sbi_ext(struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg);
+int kvm_riscv_vcpu_get_reg_sbi_ext(struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg);
+const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(
+ struct kvm_vcpu *vcpu, unsigned long extid);
int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run);

#ifdef CONFIG_RISCV_SBI_V01
diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index 92af6f3f057c..71992ff1f9dd 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -108,6 +108,22 @@ enum KVM_RISCV_ISA_EXT_ID {
KVM_RISCV_ISA_EXT_MAX,
};

+/*
+ * SBI extension IDs specific to KVM. This is not the same as the SBI
+ * extension IDs defined by the RISC-V SBI specification.
+ */
+enum KVM_RISCV_SBI_EXT_ID {
+ KVM_RISCV_SBI_EXT_V01 = 0,
+ KVM_RISCV_SBI_EXT_TIME,
+ KVM_RISCV_SBI_EXT_IPI,
+ KVM_RISCV_SBI_EXT_RFENCE,
+ KVM_RISCV_SBI_EXT_SRST,
+ KVM_RISCV_SBI_EXT_HSM,
+ KVM_RISCV_SBI_EXT_EXPERIMENTAL,
+ KVM_RISCV_SBI_EXT_VENDOR,
+ KVM_RISCV_SBI_EXT_MAX,
+};
+
/* Possible states for kvm_riscv_timer */
#define KVM_RISCV_TIMER_STATE_OFF 0
#define KVM_RISCV_TIMER_STATE_ON 1
@@ -152,6 +168,9 @@ enum KVM_RISCV_ISA_EXT_ID {
/* ISA Extension registers are mapped as type 7 */
#define KVM_REG_RISCV_ISA_EXT (0x07 << KVM_REG_RISCV_TYPE_SHIFT)

+/* SBI extension registers are mapped as type 8 */
+#define KVM_REG_RISCV_SBI_EXT (0x08 << KVM_REG_RISCV_TYPE_SHIFT)
+
#endif

#endif /* __LINUX_KVM_RISCV_H */
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 7c08567097f0..2260adaf2de8 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -594,6 +594,8 @@ static int kvm_riscv_vcpu_set_reg(struct kvm_vcpu *vcpu,
KVM_REG_RISCV_FP_D);
case KVM_REG_RISCV_ISA_EXT:
return kvm_riscv_vcpu_set_reg_isa_ext(vcpu, reg);
+ case KVM_REG_RISCV_SBI_EXT:
+ return kvm_riscv_vcpu_set_reg_sbi_ext(vcpu, reg);
default:
break;
}
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index f96991d230bf..0abb44f8f4d1 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -40,16 +40,48 @@ static const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_v01 = {
};
#endif

-static const struct kvm_vcpu_sbi_extension *sbi_ext[] = {
- &vcpu_sbi_ext_v01,
- &vcpu_sbi_ext_base,
- &vcpu_sbi_ext_time,
- &vcpu_sbi_ext_ipi,
- &vcpu_sbi_ext_rfence,
- &vcpu_sbi_ext_srst,
- &vcpu_sbi_ext_hsm,
- &vcpu_sbi_ext_experimental,
- &vcpu_sbi_ext_vendor,
+struct kvm_riscv_sbi_extension_entry {
+ enum KVM_RISCV_SBI_EXT_ID dis_idx;
+ const struct kvm_vcpu_sbi_extension *ext_ptr;
+};
+
+static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = {
+ {
+ .dis_idx = KVM_RISCV_SBI_EXT_V01,
+ .ext_ptr = &vcpu_sbi_ext_v01,
+ },
+ {
+ .dis_idx = KVM_RISCV_SBI_EXT_MAX, /* Can't be disabled */
+ .ext_ptr = &vcpu_sbi_ext_base,
+ },
+ {
+ .dis_idx = KVM_RISCV_SBI_EXT_TIME,
+ .ext_ptr = &vcpu_sbi_ext_time,
+ },
+ {
+ .dis_idx = KVM_RISCV_SBI_EXT_IPI,
+ .ext_ptr = &vcpu_sbi_ext_ipi,
+ },
+ {
+ .dis_idx = KVM_RISCV_SBI_EXT_RFENCE,
+ .ext_ptr = &vcpu_sbi_ext_rfence,
+ },
+ {
+ .dis_idx = KVM_RISCV_SBI_EXT_SRST,
+ .ext_ptr = &vcpu_sbi_ext_srst,
+ },
+ {
+ .dis_idx = KVM_RISCV_SBI_EXT_HSM,
+ .ext_ptr = &vcpu_sbi_ext_hsm,
+ },
+ {
+ .dis_idx = KVM_RISCV_SBI_EXT_EXPERIMENTAL,
+ .ext_ptr = &vcpu_sbi_ext_experimental,
+ },
+ {
+ .dis_idx = KVM_RISCV_SBI_EXT_VENDOR,
+ .ext_ptr = &vcpu_sbi_ext_vendor,
+ },
};

void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run)
@@ -108,14 +140,95 @@ int kvm_riscv_vcpu_sbi_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
return 0;
}

-const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(unsigned long extid)
+int kvm_riscv_vcpu_set_reg_sbi_ext(struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg)
+{
+ unsigned long __user *uaddr =
+ (unsigned long __user *)(unsigned long)reg->addr;
+ unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
+ KVM_REG_SIZE_MASK |
+ KVM_REG_RISCV_SBI_EXT);
+ unsigned long i, reg_val;
+ const struct kvm_riscv_sbi_extension_entry *sext = NULL;
+ struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
+
+ if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
+ return -EINVAL;
+
+ if (copy_from_user(&reg_val, uaddr, KVM_REG_SIZE(reg->id)))
+ return -EFAULT;
+
+ if (reg_num >= KVM_RISCV_SBI_EXT_MAX ||
+ (reg_val != 1 && reg_val != 0))
+ return -EINVAL;
+
+ if (vcpu->arch.ran_atleast_once)
+ return -EBUSY;
+
+ for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
+ if (sbi_ext[i].dis_idx == reg_num) {
+ sext = &sbi_ext[i];
+ break;
+ }
+ }
+ if (!sext)
+ return -ENOENT;
+
+ scontext->extension_disabled[sext->dis_idx] = !reg_val;
+
+ return 0;
+}
+
+int kvm_riscv_vcpu_get_reg_sbi_ext(struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg)
+{
+ unsigned long __user *uaddr =
+ (unsigned long __user *)(unsigned long)reg->addr;
+ unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
+ KVM_REG_SIZE_MASK |
+ KVM_REG_RISCV_SBI_EXT);
+ unsigned long i, reg_val;
+ const struct kvm_riscv_sbi_extension_entry *sext = NULL;
+ struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
+
+ if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
+ return -EINVAL;
+
+ if (reg_num >= KVM_RISCV_SBI_EXT_MAX)
+ return -EINVAL;
+
+ for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
+ if (sbi_ext[i].dis_idx == reg_num) {
+ sext = &sbi_ext[i];
+ break;
+ }
+ }
+ if (!sext)
+ return -ENOENT;
+
+ reg_val = !scontext->extension_disabled[sext->dis_idx];
+ if (copy_to_user(uaddr, &reg_val, KVM_REG_SIZE(reg->id)))
+ return -EFAULT;
+
+ return 0;
+}
+
+const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(
+ struct kvm_vcpu *vcpu, unsigned long extid)
{
- int i = 0;
+ int i;
+ const struct kvm_riscv_sbi_extension_entry *sext;
+ struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;

for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
- if (sbi_ext[i]->extid_start <= extid &&
- sbi_ext[i]->extid_end >= extid)
- return sbi_ext[i];
+ sext = &sbi_ext[i];
+ if (sext->ext_ptr->extid_start <= extid &&
+ sext->ext_ptr->extid_end >= extid) {
+ if (sext->dis_idx < KVM_RISCV_SBI_EXT_MAX &&
+ scontext->extension_disabled[sext->dis_idx])
+ return NULL;
+ return sbi_ext[i].ext_ptr;
+ }
}

return NULL;
@@ -132,7 +245,7 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
unsigned long out_val = 0;
bool ext_is_v01 = false;

- sbi_ext = kvm_vcpu_sbi_find_ext(cp->a7);
+ sbi_ext = kvm_vcpu_sbi_find_ext(vcpu, cp->a7);
if (sbi_ext && sbi_ext->handler) {
#ifdef CONFIG_RISCV_SBI_V01
if (cp->a7 >= SBI_EXT_0_1_SET_TIMER &&
diff --git a/arch/riscv/kvm/vcpu_sbi_base.c b/arch/riscv/kvm/vcpu_sbi_base.c
index 5d65c634d301..a51ed0c615bf 100644
--- a/arch/riscv/kvm/vcpu_sbi_base.c
+++ b/arch/riscv/kvm/vcpu_sbi_base.c
@@ -44,7 +44,7 @@ static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
kvm_riscv_vcpu_sbi_forward(vcpu, run);
*exit = true;
} else
- *out_val = kvm_vcpu_sbi_find_ext(cp->a0) ? 1 : 0;
+ *out_val = kvm_vcpu_sbi_find_ext(vcpu, cp->a0) ? 1 : 0;
break;
case SBI_EXT_BASE_GET_MVENDORID:
*out_val = vcpu->arch.mvendorid;
--
2.34.1