Re: [PATCH 19/26] KVM: arm64: Make struct kvm_regs userspace-only

James Morse
2020-05-26T16:29:46Z

Hi Marc,

On 22/04/2020 13:00, Marc Zyngier wrote:
> struct kvm_regs is used by userspace to indicate which register gets
> accessed by the {GET,SET}_ONE_REG API. But as we're about to refactor
> the layout of the in-kernel register structures, we need the kernel to
> move away from it.
>
> Let's make kvm_regs userspace only, and let the kernel map it to its own
> internal representation.

> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 23ebe51410f06..9fec9231b63e2 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -102,6 +102,55 @@ static int core_reg_size_from_offset(const struct kvm_vcpu *vcpu, u64 off)
> return size;
> }
>
> +static void *core_reg_addr(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> +{
> + u64 off = core_reg_offset_from_id(reg->id);
> +
> + switch (off) {

> + default:
> + return NULL;

Doesn't this switch statement catch an out of range offset, and a misaligned offset?

... We still test for those explicitly in the caller. Better safe than implicit?

> + }
> +}

With the reset thing reported by Zenghui and Zengtao on the previous patch fixed:
Reviewed-by: James Morse <james.morse@arm.com>

(otherwise struct kvm_regs isn't userspace-only!)

Thanks,

James