On Thu, Aug 13, 2020 at 02:05:16PM +0800, Peng Liang wrote:
> It's time to make ID registers configurable. When userspace (but not
> guest) want to set the values of ID registers, save the value in
> kvm_arch_vcpu so that guest can read the modified values.
>
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@xxxxxxxxxx>
> Signed-off-by: Peng Liang <liangpeng10@xxxxxxxxxx>
> ---
> arch/arm64/kvm/sys_regs.c | 23 ++++++++++++++++-------
> 1 file changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 776c2757a01e..f98635489966 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1111,6 +1111,14 @@ static u64 kvm_get_id_reg(struct kvm_vcpu *vcpu, u64 id)
> return ri->sys_val;
> }
>
> +static void kvm_set_id_reg(struct kvm_vcpu *vcpu, u64 id, u64 value)
> +{
> + struct id_reg_info *ri = kvm_id_reg(vcpu, id);
> +
> + BUG_ON(!ri);
> + ri->sys_val = value;
> +}
> +
> /* Read a sanitised cpufeature ID register by sys_reg_desc */
> static u64 read_id_reg(struct kvm_vcpu *vcpu,
> struct sys_reg_desc const *r, bool raz)
> @@ -1252,10 +1260,6 @@ static int set_id_aa64zfr0_el1(struct kvm_vcpu *vcpu,
>
> /*
> * cpufeature ID register user accessors
> - *
> - * For now, these registers are immutable for userspace, so no values
> - * are stored, and for set_id_reg() we don't allow the effective value
> - * to be changed.
> */
> static int __get_id_reg(struct kvm_vcpu *vcpu,
> const struct sys_reg_desc *rd, void __user *uaddr,
> @@ -1279,9 +1283,14 @@ static int __set_id_reg(struct kvm_vcpu *vcpu,
> if (err)
> return err;
>
> - /* This is what we mean by invariant: you can't change it. */
> - if (val != read_id_reg(vcpu, rd, raz))
> - return -EINVAL;
> + if (raz) {
> + if (val != read_id_reg(vcpu, rd, raz))
> + return -EINVAL;
> + } else {
> + u32 reg_id = sys_reg((u32)rd->Op0, (u32)rd->Op1, (u32)rd->CRn,
> + (u32)rd->CRm, (u32)rd->Op2);
> + kvm_set_id_reg(vcpu, reg_id, val);
So userspace can set the ID registers to whatever they want? I think each
register should have its own sanity checks applied before accepting the
input.
Thanks,
drew
> + }
>
> return 0;
> }
> --
> 2.18.4
>
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