RISC-V: KVM: add support for FWFT SBI extension

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>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20250523101932.1594077-14-cleger@rivosinc.com
Signed-off-by: Anup Patel <anup@brainfault.org>

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index d71d3299a335c16797fe3650d5f8107ca4e065ef..4d794573e3dbe815069dc64e01adbe8dfca95f27 100644 (file)
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -21,6 +21,7 @@
 #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>
 
@@ -263,6 +264,9 @@ 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 d678fd7e5973d16aae01e1f20634be1c57febd8e..766031e8096014a88eefbd32922fe4344556d777 100644 (file)
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -102,6 +102,7 @@ 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 (file)
index 0000000..9ba8413
--- /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 ef27d4289da1186d1f9e1f18daf65769e1927d67..a5ca0f4ce2d336a6cafaff8f422c565f7d2f2401 100644 (file)
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -205,6 +205,7 @@ 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 4b199dc3e58b438a6d55574d4e0553e8cd591840..07197395750e38b2f2dc72e788bf2f2d300fb67a 100644 (file)
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile
@@ -27,6 +27,7 @@ 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 a56c4959f9adc9a2806e712280b472a376d0abbd..01a93f4fdb161fb63598e044411390c5fc1fb3d0 100644 (file)
--- 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 (file)
index 0000000..b0f66c7
--- /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,
+};