Re: [PATCH v3 16/17] RISC-V: KVM: add support for FWFT SBI extension

On Mon, Mar 10, 2025 at 04:12:23PM +0100, Clément Léger wrote:

Add basic infrastructure to support the FWFT extension in KVM.

Signed-off-by: Clément Léger cleger@rivosinc.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 | 31 +++ 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 | 212 +++++++++++++++++++++ 7 files changed, 254 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 bb93d2995ea2..c0db61ba691a 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..ec7568e0dc1a --- /dev/null +++ b/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h @@ -0,0 +1,31 @@ +/* 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_config; +struct kvm_sbi_fwft_feature; +struct kvm_vcpu;

Should only need the forward declaration for 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 f06bc5efcd79..fa6eee1caf41 100644 --- a/arch/riscv/include/uapi/asm/kvm.h +++ b/arch/riscv/include/uapi/asm/kvm.h @@ -202,6 +202,7 @@ 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 18726096ef44..27f22e98c8f8 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..cce1e41d5490 --- /dev/null +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c @@ -0,0 +1,212 @@ +// 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
  

• *
  

• * This callback is mandatory
  

Since we're doing all this documentation, then let's also state they return SBI errors (which are longs, so we should probably return longs).

• */
  

• int (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long value);
• /**

• * @get: Get the feature current value
  

• *
  

• * This callback is mandatory
  

• */
  

• int (*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 = 0;

no need for '= 0'

• 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 = 0;
• 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 = 0;

no need for '= 0'

• 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,

+};

2.47.2

Reviewed-by: Andrew Jones ajones@ventanamicro.com