[PATCH v5 12/13] RISC-V: KVM: add support for FWFT SBI extension

Clément Léger
2025-04-17T12:36:26Z

Add basic infrastructure to support the FWFT extension in KVM.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
---
arch/riscv/include/asm/kvm_host.h | 4 +
arch/riscv/include/asm/kvm_vcpu_sbi.h | 1 +
arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h | 29 +++
arch/riscv/include/uapi/asm/kvm.h | 1 +
arch/riscv/kvm/Makefile | 1 +
arch/riscv/kvm/vcpu_sbi.c | 4 +
arch/riscv/kvm/vcpu_sbi_fwft.c | 216 +++++++++++++++++++++
7 files changed, 256 insertions(+)
create mode 100644 arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
create mode 100644 arch/riscv/kvm/vcpu_sbi_fwft.c

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 4fa02e082142..c3f880763b9a 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -19,6 +19,7 @@
#include <asm/kvm_vcpu_fp.h>
#include <asm/kvm_vcpu_insn.h>
#include <asm/kvm_vcpu_sbi.h>
+#include <asm/kvm_vcpu_sbi_fwft.h>
#include <asm/kvm_vcpu_timer.h>
#include <asm/kvm_vcpu_pmu.h>

@@ -281,6 +282,9 @@ struct kvm_vcpu_arch {
/* Performance monitoring context */
struct kvm_pmu pmu_context;

+ /* Firmware feature SBI extension context */
+ struct kvm_sbi_fwft fwft_context;
+
/* 'static' configurations which are set only once */
struct kvm_vcpu_config cfg;

diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
index cb68b3a57c8f..ffd03fed0c06 100644
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -98,6 +98,7 @@ 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_susp;
extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta;
+extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft;
extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_experimental;
extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_vendor;

diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h b/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
new file mode 100644
index 000000000000..9ba841355758
--- /dev/null
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2025 Rivos Inc.
+ *
+ * Authors:
+ * Clément Léger <cleger@rivosinc.com>
+ */
+
+#ifndef __KVM_VCPU_RISCV_FWFT_H
+#define __KVM_VCPU_RISCV_FWFT_H
+
+#include <asm/sbi.h>
+
+struct kvm_sbi_fwft_feature;
+
+struct kvm_sbi_fwft_config {
+ const struct kvm_sbi_fwft_feature *feature;
+ bool supported;
+ unsigned long flags;
+};
+
+/* FWFT data structure per vcpu */
+struct kvm_sbi_fwft {
+ struct kvm_sbi_fwft_config *configs;
+};
+
+#define vcpu_to_fwft(vcpu) (&(vcpu)->arch.fwft_context)
+
+#endif /* !__KVM_VCPU_RISCV_FWFT_H */
diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index 5f59fd226cc5..5ba77a3d9f6e 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -204,6 +204,7 @@ enum KVM_RISCV_SBI_EXT_ID {
KVM_RISCV_SBI_EXT_DBCN,
KVM_RISCV_SBI_EXT_STA,
KVM_RISCV_SBI_EXT_SUSP,
+ KVM_RISCV_SBI_EXT_FWFT,
KVM_RISCV_SBI_EXT_MAX,
};

diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
index 4e0bba91d284..06e2d52a9b88 100644
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile
@@ -26,6 +26,7 @@ kvm-y += vcpu_onereg.o
kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o
kvm-y += vcpu_sbi.o
kvm-y += vcpu_sbi_base.o
+kvm-y += vcpu_sbi_fwft.o
kvm-y += vcpu_sbi_hsm.o
kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_sbi_pmu.o
kvm-y += vcpu_sbi_replace.o
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index 50be079b5528..0748810c0252 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -78,6 +78,10 @@ static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = {
.ext_idx = KVM_RISCV_SBI_EXT_STA,
.ext_ptr = &vcpu_sbi_ext_sta,
},
+ {
+ .ext_idx = KVM_RISCV_SBI_EXT_FWFT,
+ .ext_ptr = &vcpu_sbi_ext_fwft,
+ },
{
.ext_idx = KVM_RISCV_SBI_EXT_EXPERIMENTAL,
.ext_ptr = &vcpu_sbi_ext_experimental,
diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
new file mode 100644
index 000000000000..b0f66c7bf010
--- /dev/null
+++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2025 Rivos Inc.
+ *
+ * Authors:
+ * Clément Léger <cleger@rivosinc.com>
+ */
+
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/kvm_host.h>
+#include <asm/cpufeature.h>
+#include <asm/sbi.h>
+#include <asm/kvm_vcpu_sbi.h>
+#include <asm/kvm_vcpu_sbi_fwft.h>
+
+struct kvm_sbi_fwft_feature {
+ /**
+ * @id: Feature ID
+ */
+ enum sbi_fwft_feature_t id;
+
+ /**
+ * @supported: Check if the feature is supported on the vcpu
+ *
+ * This callback is optional, if not provided the feature is assumed to
+ * be supported
+ */
+ bool (*supported)(struct kvm_vcpu *vcpu);
+
+ /**
+ * @set: Set the feature value
+ *
+ * Return SBI_SUCCESS on success or an SBI error (SBI_ERR_*)
+ *
+ * This callback is mandatory
+ */
+ long (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long value);
+
+ /**
+ * @get: Get the feature current value
+ *
+ * Return SBI_SUCCESS on success or an SBI error (SBI_ERR_*)
+ *
+ * This callback is mandatory
+ */
+ long (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long *value);
+};
+
+static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
+ SBI_FWFT_MISALIGNED_EXC_DELEG,
+ SBI_FWFT_LANDING_PAD,
+ SBI_FWFT_SHADOW_STACK,
+ SBI_FWFT_DOUBLE_TRAP,
+ SBI_FWFT_PTE_AD_HW_UPDATING,
+ SBI_FWFT_POINTER_MASKING_PMLEN,
+};
+
+static bool kvm_fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(kvm_fwft_defined_features); i++) {
+ if (kvm_fwft_defined_features[i] == feature)
+ return true;
+ }
+
+ return false;
+}
+
+static const struct kvm_sbi_fwft_feature features[] = {
+};
+
+static struct kvm_sbi_fwft_config *
+kvm_sbi_fwft_get_config(struct kvm_vcpu *vcpu, enum sbi_fwft_feature_t feature)
+{
+ int i;
+ struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
+
+ for (i = 0; i < ARRAY_SIZE(features); i++) {
+ if (fwft->configs[i].feature->id == feature)
+ return &fwft->configs[i];
+ }
+
+ return NULL;
+}
+
+static int kvm_fwft_get_feature(struct kvm_vcpu *vcpu, u32 feature,
+ struct kvm_sbi_fwft_config **conf)
+{
+ struct kvm_sbi_fwft_config *tconf;
+
+ tconf = kvm_sbi_fwft_get_config(vcpu, feature);
+ if (!tconf) {
+ if (kvm_fwft_is_defined_feature(feature))
+ return SBI_ERR_NOT_SUPPORTED;
+
+ return SBI_ERR_DENIED;
+ }
+
+ if (!tconf->supported)
+ return SBI_ERR_NOT_SUPPORTED;
+
+ *conf = tconf;
+
+ return SBI_SUCCESS;
+}
+
+static int kvm_sbi_fwft_set(struct kvm_vcpu *vcpu, u32 feature,
+ unsigned long value, unsigned long flags)
+{
+ int ret;
+ struct kvm_sbi_fwft_config *conf;
+
+ ret = kvm_fwft_get_feature(vcpu, feature, &conf);
+ if (ret)
+ return ret;
+
+ if ((flags & ~SBI_FWFT_SET_FLAG_LOCK) != 0)
+ return SBI_ERR_INVALID_PARAM;
+
+ if (conf->flags & SBI_FWFT_SET_FLAG_LOCK)
+ return SBI_ERR_DENIED_LOCKED;
+
+ conf->flags = flags;
+
+ return conf->feature->set(vcpu, conf, value);
+}
+
+static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long feature,
+ unsigned long *value)
+{
+ int ret;
+ struct kvm_sbi_fwft_config *conf;
+
+ ret = kvm_fwft_get_feature(vcpu, feature, &conf);
+ if (ret)
+ return ret;
+
+ return conf->feature->get(vcpu, conf, value);
+}
+
+static int kvm_sbi_ext_fwft_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
+ struct kvm_vcpu_sbi_return *retdata)
+{
+ int ret;
+ struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
+ unsigned long funcid = cp->a6;
+
+ switch (funcid) {
+ case SBI_EXT_FWFT_SET:
+ ret = kvm_sbi_fwft_set(vcpu, cp->a0, cp->a1, cp->a2);
+ break;
+ case SBI_EXT_FWFT_GET:
+ ret = kvm_sbi_fwft_get(vcpu, cp->a0, &retdata->out_val);
+ break;
+ default:
+ ret = SBI_ERR_NOT_SUPPORTED;
+ break;
+ }
+
+ retdata->err_val = ret;
+
+ return 0;
+}
+
+static int kvm_sbi_ext_fwft_init(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;
+
+ fwft->configs = kcalloc(ARRAY_SIZE(features), sizeof(struct kvm_sbi_fwft_config),
+ GFP_KERNEL);
+ if (!fwft->configs)
+ return -ENOMEM;
+
+ for (i = 0; i < ARRAY_SIZE(features); i++) {
+ feature = &features[i];
+ conf = &fwft->configs[i];
+ if (feature->supported)
+ conf->supported = feature->supported(vcpu);
+ else
+ conf->supported = true;
+
+ conf->feature = feature;
+ }
+
+ return 0;
+}
+
+static void kvm_sbi_ext_fwft_deinit(struct kvm_vcpu *vcpu)
+{
+ struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
+
+ kfree(fwft->configs);
+}
+
+static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
+{
+ int i;
+ struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
+
+ for (i = 0; i < ARRAY_SIZE(features); i++)
+ fwft->configs[i].flags = 0;
+}
+
+const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft = {
+ .extid_start = SBI_EXT_FWFT,
+ .extid_end = SBI_EXT_FWFT,
+ .handler = kvm_sbi_ext_fwft_handler,
+ .init = kvm_sbi_ext_fwft_init,
+ .deinit = kvm_sbi_ext_fwft_deinit,
+ .reset = kvm_sbi_ext_fwft_reset,
+};