[PATCH v3 0/4] RISC-V: KVM: Cleanup SBI extension status when disable

[PATCH v3 0/4] RISC-V: KVM: Cleanup SBI extension status when disable

[Inochi Amaoto]

KVM SBI FWFT extension has multiple internal state can be programmed
by the userspace. However, when the FWFT feature or the FWFT extension
is disabled, the internal state will be kept as it is, which may cause
some side effect for the vCPU, cleanup these state when a SBI extension
or FWFT feature is disabled.

Change from v2:
- https://lore.kernel.org/kvm/20260706021154.210289-1-inochiama@gmail.com
patch 1, 2:
1. Apply Anup's tag.
patch 3:
1. Remove the csr_dirty set.
patch 4:
1. Add a new patch that sets the csr_dirty for FWFT extension.

Change from v1:
- https://lore.kernel.org/kvm/20260701094731.1022163-1-inochiama@gmail.com
patch 2:
1. Check support callback existed before using it.

Inochi Amaoto (4):
  RISC-V: KVM: Add SBI extension validate callback
  RISC-V: KVM: Add SBI FWFT validation support
  RISC-V: KVM: Reset the SBI extension when disable it
  RISC-V: KVM: Mark the reset callback of FWFT extension always dirties
    CSR

 arch/riscv/include/asm/kvm_vcpu_sbi.h |  4 ++++
 arch/riscv/kvm/vcpu_config.c          |  2 ++
 arch/riscv/kvm/vcpu_sbi.c             | 30 +++++++++++++++++++++++++++
 arch/riscv/kvm/vcpu_sbi_fwft.c        | 27 ++++++++++++++++++++++++
 4 files changed, 63 insertions(+)

--
2.55.0

[PATCH v3 1/4] RISC-V: KVM: Add SBI extension validate callback

[Inochi Amaoto]

When user disable FWFT extension after setting any value of the
FWFT feature, the state of vCPU will be broken since the value
of disable FWFT feature is still functional.

Add the generic SBI extension validate callback so the FWFT
extension can fix its parameters before the first run.

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
---
 arch/riscv/include/asm/kvm_vcpu_sbi.h |  4 ++++
 arch/riscv/kvm/vcpu_config.c          |  2 ++
 arch/riscv/kvm/vcpu_sbi.c             | 23 +++++++++++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
index c1a7e3b40d9c..f01a2860c751 100644
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -60,6 +60,9 @@ struct kvm_vcpu_sbi_extension {
 
 	void (*reset)(struct kvm_vcpu *vcpu);
 
+	/* Allow the extension to correct its parameters before the first run */
+	void (*validate)(struct kvm_vcpu *vcpu);
+
 	unsigned long state_reg_subtype;
 	unsigned long (*get_state_reg_count)(struct kvm_vcpu *vcpu);
 	int (*get_state_reg_id)(struct kvm_vcpu *vcpu, int index, u64 *reg_id);
@@ -93,6 +96,7 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run);
 void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu);
 void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu);
 void kvm_riscv_vcpu_sbi_reset(struct kvm_vcpu *vcpu);
+void kvm_riscv_vcpu_sbi_validate(struct kvm_vcpu *vcpu);
 
 #ifdef CONFIG_RISCV_SBI_V01
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_v01;
diff --git a/arch/riscv/kvm/vcpu_config.c b/arch/riscv/kvm/vcpu_config.c
index 238418fed2b9..b68aa830aaf5 100644
--- a/arch/riscv/kvm/vcpu_config.c
+++ b/arch/riscv/kvm/vcpu_config.c
@@ -69,6 +69,8 @@ void kvm_riscv_vcpu_config_ran_once(struct kvm_vcpu *vcpu)
 
 	if (vcpu->guest_debug)
 		cfg->hedeleg &= ~BIT(EXC_BREAKPOINT);
+
+	kvm_riscv_vcpu_sbi_validate(vcpu);
 }
 
 void kvm_riscv_vcpu_config_load(struct kvm_vcpu *vcpu)
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index 46ab7b989432..b737e9a7a12a 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -723,3 +723,26 @@ void kvm_riscv_vcpu_sbi_reset(struct kvm_vcpu *vcpu)
 		ext->reset(vcpu);
 	}
 }
+
+void kvm_riscv_vcpu_sbi_validate(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
+	const struct kvm_riscv_sbi_extension_entry *entry;
+	const struct kvm_vcpu_sbi_extension *ext;
+	int idx, i;
+
+	for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
+		entry = &sbi_ext[i];
+		ext = entry->ext_ptr;
+		idx = entry->ext_idx;
+
+		if (idx < 0 || idx >= ARRAY_SIZE(scontext->ext_status))
+			continue;
+
+		if (scontext->ext_status[idx] != KVM_RISCV_SBI_EXT_STATUS_ENABLED ||
+		    !ext->validate)
+			continue;
+
+		ext->validate(vcpu);
+	}
+}
-- 
2.55.0

[PATCH v3 2/4] RISC-V: KVM: Add SBI FWFT validation support

[Inochi Amaoto]

Since the KVM SBI has extension parameters validation support,
implement it for the SBI FWFT support.

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
---
 arch/riscv/kvm/vcpu_sbi_fwft.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
index 03153fd8d15f..56fb59afe02a 100644
--- a/arch/riscv/kvm/vcpu_sbi_fwft.c
+++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
@@ -603,6 +603,30 @@ static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
 	}
 }
 
+static void kvm_sbi_ext_fwft_validate(struct kvm_vcpu *vcpu)
+{
+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
+	const struct kvm_sbi_fwft_feature *feature;
+	struct kvm_sbi_fwft_config *conf;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(features); i++) {
+		feature = &features[i];
+		conf = &fwft->configs[i];
+		if (!conf->supported)
+			continue;
+
+		if (!feature->supported || feature->supported(vcpu))
+			continue;
+
+		conf->enabled = false;
+		conf->flags = 0;
+
+		if (feature->reset)
+			feature->reset(vcpu);
+	}
+}
+
 static unsigned long kvm_sbi_ext_fwft_get_reg_count(struct kvm_vcpu *vcpu)
 {
 	unsigned long max_reg_count = sizeof(struct kvm_riscv_sbi_fwft) / sizeof(unsigned long);
@@ -755,6 +779,7 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft = {
 	.init = kvm_sbi_ext_fwft_init,
 	.deinit = kvm_sbi_ext_fwft_deinit,
 	.reset = kvm_sbi_ext_fwft_reset,
+	.validate = kvm_sbi_ext_fwft_validate,
 	.state_reg_subtype = KVM_REG_RISCV_SBI_FWFT,
 	.get_state_reg_count = kvm_sbi_ext_fwft_get_reg_count,
 	.get_state_reg_id = kvm_sbi_ext_fwft_get_reg_id,
-- 
2.55.0

[PATCH v3 3/4] RISC-V: KVM: Reset the SBI extension when disable it

[Inochi Amaoto]

The SBI extension validation callback can only fix the parameter if
the extension is enabled. However, if the extension is disabled after
modifty some parameters, the state of the extension is still broken.

Reset the extension when the extension is disabled so it can have
a clear context.

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
---
 arch/riscv/kvm/vcpu_sbi.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index b737e9a7a12a..1c4f874368fb 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -221,6 +221,7 @@ static int riscv_vcpu_set_sbi_ext_single(struct kvm_vcpu *vcpu,
 {
 	struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
 	const struct kvm_riscv_sbi_extension_entry *sext;
+	const struct kvm_vcpu_sbi_extension *ext;
 
 	if (reg_val != 1 && reg_val != 0)
 		return -EINVAL;
@@ -229,6 +230,12 @@ static int riscv_vcpu_set_sbi_ext_single(struct kvm_vcpu *vcpu,
 	if (!sext || scontext->ext_status[sext->ext_idx] == KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE)
 		return -ENOENT;
 
+	ext = sext->ext_ptr;
+
+	if (!reg_val && scontext->ext_status[sext->ext_idx] == KVM_RISCV_SBI_EXT_STATUS_ENABLED &&
+	    ext->reset)
+		ext->reset(vcpu);
+
 	scontext->ext_status[sext->ext_idx] = (reg_val) ?
 			KVM_RISCV_SBI_EXT_STATUS_ENABLED :
 			KVM_RISCV_SBI_EXT_STATUS_DISABLED;
-- 
2.55.0

[PATCH v3 4/4] RISC-V: KVM: Mark the reset callback of FWFT extension always dirties CSR

[Inochi Amaoto]

As the CSR is only flushed when the csr_dirty is set, always set the
csr_dirty field in kvm_sbi_ext_fwft_reset() so the CSR change can take
effect immediately. This unconditional set should be safe as all
supported FWFT features change the CSR state currently.

Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
---
 arch/riscv/kvm/vcpu_sbi_fwft.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
index 56fb59afe02a..2e35e7e12327 100644
--- a/arch/riscv/kvm/vcpu_sbi_fwft.c
+++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
@@ -601,6 +601,8 @@ static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
 		if (feature->reset)
 			feature->reset(vcpu);
 	}
+
+	vcpu->arch.csr_dirty = true;
 }
 
 static void kvm_sbi_ext_fwft_validate(struct kvm_vcpu *vcpu)
-- 
2.55.0

Re: [PATCH v3 3/4] RISC-V: KVM: Reset the SBI extension when disable it

[Anup Patel]

On Thu, Jul 30, 2026 at 4:55 AM Inochi Amaoto <inochiama@gmail.com> wrote:
>
> The SBI extension validation callback can only fix the parameter if
> the extension is enabled. However, if the extension is disabled after
> modifty some parameters, the state of the extension is still broken.
>
> Reset the extension when the extension is disabled so it can have
> a clear context.
>
> Signed-off-by: Inochi Amaoto <inochiama@gmail.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Thanks,
Anup

> ---
>  arch/riscv/kvm/vcpu_sbi.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> index b737e9a7a12a..1c4f874368fb 100644
> --- a/arch/riscv/kvm/vcpu_sbi.c
> +++ b/arch/riscv/kvm/vcpu_sbi.c
> @@ -221,6 +221,7 @@ static int riscv_vcpu_set_sbi_ext_single(struct kvm_vcpu *vcpu,
>  {
>         struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
>         const struct kvm_riscv_sbi_extension_entry *sext;
> +       const struct kvm_vcpu_sbi_extension *ext;
>
>         if (reg_val != 1 && reg_val != 0)
>                 return -EINVAL;
> @@ -229,6 +230,12 @@ static int riscv_vcpu_set_sbi_ext_single(struct kvm_vcpu *vcpu,
>         if (!sext || scontext->ext_status[sext->ext_idx] == KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE)
>                 return -ENOENT;
>
> +       ext = sext->ext_ptr;
> +
> +       if (!reg_val && scontext->ext_status[sext->ext_idx] == KVM_RISCV_SBI_EXT_STATUS_ENABLED &&
> +           ext->reset)
> +               ext->reset(vcpu);
> +
>         scontext->ext_status[sext->ext_idx] = (reg_val) ?
>                         KVM_RISCV_SBI_EXT_STATUS_ENABLED :
>                         KVM_RISCV_SBI_EXT_STATUS_DISABLED;
> --
> 2.55.0
>

Re: [PATCH v3 4/4] RISC-V: KVM: Mark the reset callback of FWFT extension always dirties CSR

[Anup Patel]

On Thu, Jul 30, 2026 at 4:55 AM Inochi Amaoto <inochiama@gmail.com> wrote:
>
> As the CSR is only flushed when the csr_dirty is set, always set the
> csr_dirty field in kvm_sbi_ext_fwft_reset() so the CSR change can take
> effect immediately. This unconditional set should be safe as all
> supported FWFT features change the CSR state currently.
>
> Signed-off-by: Inochi Amaoto <inochiama@gmail.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Thanks,
Anup

> ---
>  arch/riscv/kvm/vcpu_sbi_fwft.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
> index 56fb59afe02a..2e35e7e12327 100644
> --- a/arch/riscv/kvm/vcpu_sbi_fwft.c
> +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
> @@ -601,6 +601,8 @@ static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
>                 if (feature->reset)
>                         feature->reset(vcpu);
>         }
> +
> +       vcpu->arch.csr_dirty = true;
>  }
>
>  static void kvm_sbi_ext_fwft_validate(struct kvm_vcpu *vcpu)
> --
> 2.55.0
>

Re: [PATCH v3 0/4] RISC-V: KVM: Cleanup SBI extension status when disable

[Anup Patel]

On Thu, Jul 30, 2026 at 4:55 AM Inochi Amaoto <inochiama@gmail.com> wrote:
>
> KVM SBI FWFT extension has multiple internal state can be programmed
> by the userspace. However, when the FWFT feature or the FWFT extension
> is disabled, the internal state will be kept as it is, which may cause
> some side effect for the vCPU, cleanup these state when a SBI extension
> or FWFT feature is disabled.
>
> Change from v2:
> - https://lore.kernel.org/kvm/20260706021154.210289-1-inochiama@gmail.com
> patch 1, 2:
> 1. Apply Anup's tag.
> patch 3:
> 1. Remove the csr_dirty set.
> patch 4:
> 1. Add a new patch that sets the csr_dirty for FWFT extension.
>
> Change from v1:
> - https://lore.kernel.org/kvm/20260701094731.1022163-1-inochiama@gmail.com
> patch 2:
> 1. Check support callback existed before using it.
>
> Inochi Amaoto (4):
>   RISC-V: KVM: Add SBI extension validate callback
>   RISC-V: KVM: Add SBI FWFT validation support
>   RISC-V: KVM: Reset the SBI extension when disable it
>   RISC-V: KVM: Mark the reset callback of FWFT extension always dirties
>     CSR
>
>  arch/riscv/include/asm/kvm_vcpu_sbi.h |  4 ++++
>  arch/riscv/kvm/vcpu_config.c          |  2 ++
>  arch/riscv/kvm/vcpu_sbi.c             | 30 +++++++++++++++++++++++++++
>  arch/riscv/kvm/vcpu_sbi_fwft.c        | 27 ++++++++++++++++++++++++
>  4 files changed, 63 insertions(+)
>
> --
> 2.55.0
>

Queued this series for Linux-7.3

Thanks,
Anup