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RISC-V: KVM: Introduce ISA extension register 

Currently, there is no provision for vmm (qemu-kvm or kvmtool) to
query about multiple-letter ISA extensions. The config register
is only used for base single letter ISA extensions.

A new ISA extension register is added that will allow the vmm
to query about any ISA extension one at a time. It is enabled for
both single letter or multi-letter ISA extensions. The ISA extension
register is useful to if the vmm requires to retrieve/set single
extension while the config register should be used if all the base
ISA extension required to retrieve or set.

For any multi-letter ISA extensions, the new register interface
must be used.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Atish Patra 2022-05-09 11:29:37 -07:00 committed by Anup Patel
parent 92e450507d
commit affa28e4d0
2 changed files with 119 additions and 0 deletions
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20
arch/riscv/include/uapi/asm/kvm.h
View File

@ -82,6 +82,23 @@ struct kvm_riscv_timer {
__u64 state;
};
/*
* ISA extension IDs specific to KVM. This is not the same as the host ISA
* extension IDs as that is internal to the host and should not be exposed
* to the guest. This should always be contiguous to keep the mapping simple
* in KVM implementation.
*/
enum KVM_RISCV_ISA_EXT_ID {
KVM_RISCV_ISA_EXT_A = 0,
KVM_RISCV_ISA_EXT_C,
KVM_RISCV_ISA_EXT_D,
KVM_RISCV_ISA_EXT_F,
KVM_RISCV_ISA_EXT_H,
KVM_RISCV_ISA_EXT_I,
KVM_RISCV_ISA_EXT_M,
KVM_RISCV_ISA_EXT_MAX,
};
/* Possible states for kvm_riscv_timer */
#define KVM_RISCV_TIMER_STATE_OFF 0
#define KVM_RISCV_TIMER_STATE_ON 1
@ -123,6 +140,9 @@ struct kvm_riscv_timer {
#define KVM_REG_RISCV_FP_D_REG(name) \
(offsetof(struct __riscv_d_ext_state, name) / sizeof(__u64))
/* ISA Extension registers are mapped as type 7 */
#define KVM_REG_RISCV_ISA_EXT (0x07 << KVM_REG_RISCV_TYPE_SHIFT)
#endif
#endif /* __LINUX_KVM_RISCV_H */

99
arch/riscv/kvm/vcpu.c
View File

@ -374,6 +374,101 @@ static int kvm_riscv_vcpu_set_reg_csr(struct kvm_vcpu *vcpu,
return 0;
}
/* Mapping between KVM ISA Extension ID & Host ISA extension ID */
static unsigned long kvm_isa_ext_arr[] = {
RISCV_ISA_EXT_a,
RISCV_ISA_EXT_c,
RISCV_ISA_EXT_d,
RISCV_ISA_EXT_f,
RISCV_ISA_EXT_h,
RISCV_ISA_EXT_i,
RISCV_ISA_EXT_m,
};
static int kvm_riscv_vcpu_get_reg_isa_ext(struct kvm_vcpu *vcpu,
const struct kvm_one_reg *reg)
{
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 |
KVM_REG_RISCV_ISA_EXT);
unsigned long reg_val = 0;
unsigned long host_isa_ext;
if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
return -EINVAL;
if (reg_num >= KVM_RISCV_ISA_EXT_MAX || reg_num >= ARRAY_SIZE(kvm_isa_ext_arr))
return -EINVAL;
host_isa_ext = kvm_isa_ext_arr[reg_num];
if (__riscv_isa_extension_available(&vcpu->arch.isa, host_isa_ext))
reg_val = 1; /* Mark the given extension as available */
if (copy_to_user(uaddr, &reg_val, KVM_REG_SIZE(reg->id)))
return -EFAULT;
return 0;
}
static int kvm_riscv_vcpu_set_reg_isa_ext(struct kvm_vcpu *vcpu,
const struct kvm_one_reg *reg)
{
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 |
KVM_REG_RISCV_ISA_EXT);
unsigned long reg_val;
unsigned long host_isa_ext;
unsigned long host_isa_ext_mask;
if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
return -EINVAL;
if (reg_num >= KVM_RISCV_ISA_EXT_MAX || reg_num >= ARRAY_SIZE(kvm_isa_ext_arr))
return -EINVAL;
if (copy_from_user(&reg_val, uaddr, KVM_REG_SIZE(reg->id)))
return -EFAULT;
host_isa_ext = kvm_isa_ext_arr[reg_num];
if (!__riscv_isa_extension_available(NULL, host_isa_ext))
return -EOPNOTSUPP;
if (host_isa_ext >= RISCV_ISA_EXT_BASE &&
host_isa_ext < RISCV_ISA_EXT_MAX) {
/*
* Multi-letter ISA extension. Currently there is no provision
* to enable/disable the multi-letter ISA extensions for guests.
* Return success if the request is to enable any ISA extension
* that is available in the hardware.
* Return -EOPNOTSUPP otherwise.
*/
if (!reg_val)
return -EOPNOTSUPP;
else
return 0;
}
/* Single letter base ISA extension */
if (!vcpu->arch.ran_atleast_once) {
host_isa_ext_mask = BIT_MASK(host_isa_ext);
if (!reg_val && (host_isa_ext_mask & KVM_RISCV_ISA_DISABLE_ALLOWED))
vcpu->arch.isa &= ~host_isa_ext_mask;
else
vcpu->arch.isa |= host_isa_ext_mask;
vcpu->arch.isa &= riscv_isa_extension_base(NULL);
vcpu->arch.isa &= KVM_RISCV_ISA_ALLOWED;
kvm_riscv_vcpu_fp_reset(vcpu);
} else {
return -EOPNOTSUPP;
}
return 0;
}
static int kvm_riscv_vcpu_set_reg(struct kvm_vcpu *vcpu,
const struct kvm_one_reg *reg)
{
@ -391,6 +486,8 @@ static int kvm_riscv_vcpu_set_reg(struct kvm_vcpu *vcpu,
else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_FP_D)
return kvm_riscv_vcpu_set_reg_fp(vcpu, reg,
KVM_REG_RISCV_FP_D);
else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_ISA_EXT)
return kvm_riscv_vcpu_set_reg_isa_ext(vcpu, reg);
return -EINVAL;
}
@ -412,6 +509,8 @@ static int kvm_riscv_vcpu_get_reg(struct kvm_vcpu *vcpu,
else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_FP_D)
return kvm_riscv_vcpu_get_reg_fp(vcpu, reg,
KVM_REG_RISCV_FP_D);
else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_ISA_EXT)
return kvm_riscv_vcpu_get_reg_isa_ext(vcpu, reg);
return -EINVAL;
}