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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>
1 parent 76eeb9b commit 6b72fd1

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‎arch/riscv/include/asm/kvm_host.h‎

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@@ -21,6 +21,7 @@
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#include <asm/kvm_vcpu_fp.h>
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#include <asm/kvm_vcpu_insn.h>
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#include <asm/kvm_vcpu_sbi.h>
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#include <asm/kvm_vcpu_sbi_fwft.h>
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#include <asm/kvm_vcpu_timer.h>
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#include <asm/kvm_vcpu_pmu.h>
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@@ -263,6 +264,9 @@ struct kvm_vcpu_arch {
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/* Performance monitoring context */
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struct kvm_pmu pmu_context;
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/* Firmware feature SBI extension context */
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struct kvm_sbi_fwft fwft_context;
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/* 'static' configurations which are set only once */
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struct kvm_vcpu_config cfg;
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‎arch/riscv/include/asm/kvm_vcpu_sbi.h‎

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@@ -102,6 +102,7 @@ extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_hsm;
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extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_dbcn;
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extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_susp;
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extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta;
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extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft;
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extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_experimental;
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extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_vendor;
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‎arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h‎

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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (c) 2025 Rivos Inc.
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*
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* Authors:
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* Clément Léger <cleger@rivosinc.com>
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*/
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#ifndef __KVM_VCPU_RISCV_FWFT_H
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#define __KVM_VCPU_RISCV_FWFT_H
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#include <asm/sbi.h>
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struct kvm_sbi_fwft_feature;
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struct kvm_sbi_fwft_config {
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const struct kvm_sbi_fwft_feature *feature;
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bool supported;
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unsigned long flags;
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};
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/* FWFT data structure per vcpu */
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struct kvm_sbi_fwft {
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struct kvm_sbi_fwft_config *configs;
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};
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#define vcpu_to_fwft(vcpu) (&(vcpu)->arch.fwft_context)
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#endif /* !__KVM_VCPU_RISCV_FWFT_H */

‎arch/riscv/include/uapi/asm/kvm.h‎

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@@ -205,6 +205,7 @@ enum KVM_RISCV_SBI_EXT_ID {
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KVM_RISCV_SBI_EXT_DBCN,
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KVM_RISCV_SBI_EXT_STA,
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KVM_RISCV_SBI_EXT_SUSP,
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KVM_RISCV_SBI_EXT_FWFT,
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KVM_RISCV_SBI_EXT_MAX,
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};
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‎arch/riscv/kvm/Makefile‎

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@@ -27,6 +27,7 @@ kvm-y += vcpu_onereg.o
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kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o
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kvm-y += vcpu_sbi.o
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kvm-y += vcpu_sbi_base.o
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kvm-y += vcpu_sbi_fwft.o
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kvm-y += vcpu_sbi_hsm.o
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kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_sbi_pmu.o
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kvm-y += vcpu_sbi_replace.o

‎arch/riscv/kvm/vcpu_sbi.c‎

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@@ -78,6 +78,10 @@ static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = {
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.ext_idx = KVM_RISCV_SBI_EXT_STA,
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.ext_ptr = &vcpu_sbi_ext_sta,
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},
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{
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.ext_idx = KVM_RISCV_SBI_EXT_FWFT,
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.ext_ptr = &vcpu_sbi_ext_fwft,
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},
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{
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.ext_idx = KVM_RISCV_SBI_EXT_EXPERIMENTAL,
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.ext_ptr = &vcpu_sbi_ext_experimental,

‎arch/riscv/kvm/vcpu_sbi_fwft.c‎

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// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2025 Rivos Inc.
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*
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* Authors:
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* Clément Léger <cleger@rivosinc.com>
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*/
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#include <linux/errno.h>
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#include <linux/err.h>
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#include <linux/kvm_host.h>
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#include <asm/cpufeature.h>
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#include <asm/sbi.h>
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#include <asm/kvm_vcpu_sbi.h>
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#include <asm/kvm_vcpu_sbi_fwft.h>
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struct kvm_sbi_fwft_feature {
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/**
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* @id: Feature ID
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*/
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enum sbi_fwft_feature_t id;
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/**
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* @supported: Check if the feature is supported on the vcpu
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*
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* This callback is optional, if not provided the feature is assumed to
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* be supported
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*/
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bool (*supported)(struct kvm_vcpu *vcpu);
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/**
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* @set: Set the feature value
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*
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* Return SBI_SUCCESS on success or an SBI error (SBI_ERR_*)
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*
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* This callback is mandatory
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*/
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long (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long value);
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/**
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* @get: Get the feature current value
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*
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* Return SBI_SUCCESS on success or an SBI error (SBI_ERR_*)
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*
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* This callback is mandatory
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*/
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long (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long *value);
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};
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static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
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SBI_FWFT_MISALIGNED_EXC_DELEG,
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SBI_FWFT_LANDING_PAD,
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SBI_FWFT_SHADOW_STACK,
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SBI_FWFT_DOUBLE_TRAP,
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SBI_FWFT_PTE_AD_HW_UPDATING,
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SBI_FWFT_POINTER_MASKING_PMLEN,
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};
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static bool kvm_fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
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{
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int i;
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for (i = 0; i < ARRAY_SIZE(kvm_fwft_defined_features); i++) {
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if (kvm_fwft_defined_features[i] == feature)
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return true;
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}
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return false;
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}
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static const struct kvm_sbi_fwft_feature features[] = {
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};
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static struct kvm_sbi_fwft_config *
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kvm_sbi_fwft_get_config(struct kvm_vcpu *vcpu, enum sbi_fwft_feature_t feature)
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{
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int i;
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struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
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for (i = 0; i < ARRAY_SIZE(features); i++) {
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if (fwft->configs[i].feature->id == feature)
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return &fwft->configs[i];
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}
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return NULL;
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}
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static int kvm_fwft_get_feature(struct kvm_vcpu *vcpu, u32 feature,
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struct kvm_sbi_fwft_config **conf)
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{
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struct kvm_sbi_fwft_config *tconf;
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tconf = kvm_sbi_fwft_get_config(vcpu, feature);
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if (!tconf) {
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if (kvm_fwft_is_defined_feature(feature))
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return SBI_ERR_NOT_SUPPORTED;
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return SBI_ERR_DENIED;
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}
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if (!tconf->supported)
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return SBI_ERR_NOT_SUPPORTED;
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*conf = tconf;
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return SBI_SUCCESS;
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}
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static int kvm_sbi_fwft_set(struct kvm_vcpu *vcpu, u32 feature,
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unsigned long value, unsigned long flags)
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{
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int ret;
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struct kvm_sbi_fwft_config *conf;
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ret = kvm_fwft_get_feature(vcpu, feature, &conf);
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if (ret)
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return ret;
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if ((flags & ~SBI_FWFT_SET_FLAG_LOCK) != 0)
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return SBI_ERR_INVALID_PARAM;
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if (conf->flags & SBI_FWFT_SET_FLAG_LOCK)
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return SBI_ERR_DENIED_LOCKED;
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conf->flags = flags;
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return conf->feature->set(vcpu, conf, value);
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}
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static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long feature,
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unsigned long *value)
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{
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int ret;
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struct kvm_sbi_fwft_config *conf;
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ret = kvm_fwft_get_feature(vcpu, feature, &conf);
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if (ret)
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return ret;
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return conf->feature->get(vcpu, conf, value);
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}
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static int kvm_sbi_ext_fwft_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
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struct kvm_vcpu_sbi_return *retdata)
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{
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int ret;
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struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
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unsigned long funcid = cp->a6;
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switch (funcid) {
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case SBI_EXT_FWFT_SET:
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ret = kvm_sbi_fwft_set(vcpu, cp->a0, cp->a1, cp->a2);
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break;
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case SBI_EXT_FWFT_GET:
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ret = kvm_sbi_fwft_get(vcpu, cp->a0, &retdata->out_val);
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break;
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default:
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ret = SBI_ERR_NOT_SUPPORTED;
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break;
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}
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retdata->err_val = ret;
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return 0;
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}
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static int kvm_sbi_ext_fwft_init(struct kvm_vcpu *vcpu)
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{
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struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
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const struct kvm_sbi_fwft_feature *feature;
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struct kvm_sbi_fwft_config *conf;
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int i;
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fwft->configs = kcalloc(ARRAY_SIZE(features), sizeof(struct kvm_sbi_fwft_config),
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GFP_KERNEL);
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if (!fwft->configs)
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return -ENOMEM;
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for (i = 0; i < ARRAY_SIZE(features); i++) {
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feature = &features[i];
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conf = &fwft->configs[i];
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if (feature->supported)
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conf->supported = feature->supported(vcpu);
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else
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conf->supported = true;
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conf->feature = feature;
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}
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return 0;
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}
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static void kvm_sbi_ext_fwft_deinit(struct kvm_vcpu *vcpu)
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{
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struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
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kfree(fwft->configs);
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}
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static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
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{
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int i;
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struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
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for (i = 0; i < ARRAY_SIZE(features); i++)
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fwft->configs[i].flags = 0;
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}
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const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft = {
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.extid_start = SBI_EXT_FWFT,
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.extid_end = SBI_EXT_FWFT,
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.handler = kvm_sbi_ext_fwft_handler,
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.init = kvm_sbi_ext_fwft_init,
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.deinit = kvm_sbi_ext_fwft_deinit,
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.reset = kvm_sbi_ext_fwft_reset,
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};

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