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linux/arch/riscv/kvm/vcpu_fp.c
Daniel Henrique Barboza 2a88f38cd5 RISC-V: KVM: return ENOENT in *_one_reg() when reg is unknown 
get_one_reg() and set_one_reg() are returning EINVAL errors for almost
everything: if a reg doesn't exist, if a reg ID is malformatted, if the
associated CPU extension that implements the reg isn't present in the
host, and for set_one_reg() if the value being written is invalid.

This isn't wrong according to the existing KVM API docs (EINVAL can be
used when there's no such register) but adding more ENOENT instances
will make easier for userspace to understand what went wrong.

Existing userspaces can be affected by this error code change. We
checked a few. As of current upstream code, crosvm doesn't check for any
particular errno code when using kvm_(get|set)_one_reg(). Neither does
QEMU. rust-vmm doesn't have kvm-riscv support yet. Thus we have a good
chance of changing these error codes now while the KVM RISC-V ecosystem
is still new, minimizing user impact.

Change all get_one_reg() and set_one_reg() implementations to return
-ENOENT at all "no such register" cases.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
2023-08-08 17:25:42 +05:30

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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2021 Western Digital Corporation or its affiliates.
*
* Authors:
* Atish Patra <atish.patra@wdc.com>
* Anup Patel <anup.patel@wdc.com>
*/
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/kvm_host.h>
#include <linux/uaccess.h>
#include <asm/hwcap.h>
#ifdef CONFIG_FPU
void kvm_riscv_vcpu_fp_reset(struct kvm_vcpu *vcpu)
{
struct kvm_cpu_context *cntx = &vcpu->arch.guest_context;
cntx->sstatus &= ~SR_FS;
if (riscv_isa_extension_available(vcpu->arch.isa, f) ||
riscv_isa_extension_available(vcpu->arch.isa, d))
cntx->sstatus |= SR_FS_INITIAL;
else
cntx->sstatus |= SR_FS_OFF;
}
static void kvm_riscv_vcpu_fp_clean(struct kvm_cpu_context *cntx)
{
cntx->sstatus &= ~SR_FS;
cntx->sstatus |= SR_FS_CLEAN;
}
void kvm_riscv_vcpu_guest_fp_save(struct kvm_cpu_context *cntx,
const unsigned long *isa)
{
if ((cntx->sstatus & SR_FS) == SR_FS_DIRTY) {
if (riscv_isa_extension_available(isa, d))
__kvm_riscv_fp_d_save(cntx);
else if (riscv_isa_extension_available(isa, f))
__kvm_riscv_fp_f_save(cntx);
kvm_riscv_vcpu_fp_clean(cntx);
}
}
void kvm_riscv_vcpu_guest_fp_restore(struct kvm_cpu_context *cntx,
const unsigned long *isa)
{
if ((cntx->sstatus & SR_FS) != SR_FS_OFF) {
if (riscv_isa_extension_available(isa, d))
__kvm_riscv_fp_d_restore(cntx);
else if (riscv_isa_extension_available(isa, f))
__kvm_riscv_fp_f_restore(cntx);
kvm_riscv_vcpu_fp_clean(cntx);
}
}
void kvm_riscv_vcpu_host_fp_save(struct kvm_cpu_context *cntx)
{
/* No need to check host sstatus as it can be modified outside */
if (riscv_isa_extension_available(NULL, d))
__kvm_riscv_fp_d_save(cntx);
else if (riscv_isa_extension_available(NULL, f))
__kvm_riscv_fp_f_save(cntx);
}
void kvm_riscv_vcpu_host_fp_restore(struct kvm_cpu_context *cntx)
{
if (riscv_isa_extension_available(NULL, d))
__kvm_riscv_fp_d_restore(cntx);
else if (riscv_isa_extension_available(NULL, f))
__kvm_riscv_fp_f_restore(cntx);
}
#endif
int kvm_riscv_vcpu_get_reg_fp(struct kvm_vcpu *vcpu,
const struct kvm_one_reg *reg,
unsigned long rtype)
{
struct kvm_cpu_context *cntx = &vcpu->arch.guest_context;
unsigned long __user *uaddr =
(unsigned long __user *)(unsigned long)reg->addr;
unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
KVM_REG_SIZE_MASK |
rtype);
void *reg_val;
if ((rtype == KVM_REG_RISCV_FP_F) &&
riscv_isa_extension_available(vcpu->arch.isa, f)) {
if (KVM_REG_SIZE(reg->id) != sizeof(u32))
return -EINVAL;
if (reg_num == KVM_REG_RISCV_FP_F_REG(fcsr))
reg_val = &cntx->fp.f.fcsr;
else if ((KVM_REG_RISCV_FP_F_REG(f[0]) <= reg_num) &&
reg_num <= KVM_REG_RISCV_FP_F_REG(f[31]))
reg_val = &cntx->fp.f.f[reg_num];
else
return -ENOENT;
} else if ((rtype == KVM_REG_RISCV_FP_D) &&
riscv_isa_extension_available(vcpu->arch.isa, d)) {
if (reg_num == KVM_REG_RISCV_FP_D_REG(fcsr)) {
if (KVM_REG_SIZE(reg->id) != sizeof(u32))
return -EINVAL;
reg_val = &cntx->fp.d.fcsr;
} else if ((KVM_REG_RISCV_FP_D_REG(f[0]) <= reg_num) &&
reg_num <= KVM_REG_RISCV_FP_D_REG(f[31])) {
if (KVM_REG_SIZE(reg->id) != sizeof(u64))
return -EINVAL;
reg_val = &cntx->fp.d.f[reg_num];
} else
return -ENOENT;
} else
return -ENOENT;
if (copy_to_user(uaddr, reg_val, KVM_REG_SIZE(reg->id)))
return -EFAULT;
return 0;
}
int kvm_riscv_vcpu_set_reg_fp(struct kvm_vcpu *vcpu,
const struct kvm_one_reg *reg,
unsigned long rtype)
{
struct kvm_cpu_context *cntx = &vcpu->arch.guest_context;
unsigned long __user *uaddr =
(unsigned long __user *)(unsigned long)reg->addr;
unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
KVM_REG_SIZE_MASK |
rtype);
void *reg_val;
if ((rtype == KVM_REG_RISCV_FP_F) &&
riscv_isa_extension_available(vcpu->arch.isa, f)) {
if (KVM_REG_SIZE(reg->id) != sizeof(u32))
return -EINVAL;
if (reg_num == KVM_REG_RISCV_FP_F_REG(fcsr))
reg_val = &cntx->fp.f.fcsr;
else if ((KVM_REG_RISCV_FP_F_REG(f[0]) <= reg_num) &&
reg_num <= KVM_REG_RISCV_FP_F_REG(f[31]))
reg_val = &cntx->fp.f.f[reg_num];
else
return -ENOENT;
} else if ((rtype == KVM_REG_RISCV_FP_D) &&
riscv_isa_extension_available(vcpu->arch.isa, d)) {
if (reg_num == KVM_REG_RISCV_FP_D_REG(fcsr)) {
if (KVM_REG_SIZE(reg->id) != sizeof(u32))
return -EINVAL;
reg_val = &cntx->fp.d.fcsr;
} else if ((KVM_REG_RISCV_FP_D_REG(f[0]) <= reg_num) &&
reg_num <= KVM_REG_RISCV_FP_D_REG(f[31])) {
if (KVM_REG_SIZE(reg->id) != sizeof(u64))
return -EINVAL;
reg_val = &cntx->fp.d.f[reg_num];
} else
return -ENOENT;
} else
return -ENOENT;
if (copy_from_user(reg_val, uaddr, KVM_REG_SIZE(reg->id)))
return -EFAULT;
return 0;
}
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