Re: [PATCH v2 14/15] RISC-V: KVM: add support for FWFT SBI extension

On 11/02/2025 06:57, Deepak Gupta wrote:

On Mon, Feb 10, 2025 at 10:35:47PM +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 |  37 ++++ 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             | 187 +++++++++++++++++++++ 7 files changed, 235 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..5782517f6e08 --- /dev/null +++ b/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h @@ -0,0 +1,37 @@ +/* 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_vcpu;

Can we add some comments here for future fwft providers along below lines?

Reason being, patch defaults to `conf->supported = true` if `supported` fn pointer in `kvm_sbi_fwft_feature` was NULL. Although `kvm_sbi_fwft_set/get` does get/set fn pointers (it would happen even if `supported` fn pointer was NULL).

Yes sure, I'll add some kernel doc comments.

Thanks,

Clément

...

+struct kvm_sbi_fwft_feature { +    enum sbi_fwft_feature_t id;

/* If function not provided, KVM will default assume to be true */

...

+    bool (*supported)(struct kvm_vcpu *vcpu);

/* Must always provide function pointers for get/set */

...

+    int (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long value); +    int (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long *value);

...

+};

+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 f81f06f82650..3b37deaed4e7 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..fe608bf16558 --- /dev/null +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c @@ -0,0 +1,187 @@ +// 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>

+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; +    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, unsigned long feature, +                struct kvm_sbi_fwft_config **conf) +{ +    struct kvm_sbi_fwft_config *tconf;

+    /* Feature are defined as 32 bits identifiers */ +    if (feature & ~(BIT_ULL(32) - 1)) +        return SBI_ERR_INVALID_PARAM;

+    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, unsigned long 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; +    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