Re: [PATCH v3 1/3] KVM: arm64: Add pre_fault_memory implementation

["Thomson, Jack" <jackabt.amazon@gmail.com>]

On 24/11/2025 12:54 pm, Marc Zyngier wrote:
> On Mon, 24 Nov 2025 11:34:38 +0000,
> Marc Zyngier <maz@kernel.org> wrote:
>>
>> On Wed, 19 Nov 2025 15:49:08 +0000,
>> Jack Thomson <jackabt.amazon@gmail.com> wrote:
>>>
> 
> [...]
> 
>>> +	fault_info->hpfar_el2 = HPFAR_EL2_NS |
>>> +		FIELD_PREP(HPFAR_EL2_FIPA, ipa >> 12);
>>> +
>>> +	if (kvm_slot_has_gmem(memslot)) {
>>> +		ret = gmem_abort(vcpu, ipa, NULL, memslot, false);
>>> +	} else {
>>> +		hva = gfn_to_hva_memslot_prot(memslot, gfn, NULL);
>>> +		if (kvm_is_error_hva(hva)) {
>>> +			ret = -EFAULT;
>>> +			goto out;
>>> +		}
>>> +		ret = user_mem_abort(vcpu, ipa, NULL, memslot, &page_size, hva,
>>> +				     false);
>>> +	}
> 
> And thinking of it a bit more, this is completely broken. What happens
> if the vcpu is in a nested context? You just populate random pages in
> an IPA space that is not relevant at all, corrupting the guest state.
> 
> You must correctly handle the context the vcpu is in, instead of
> assuming that this is the canonical context. This means going via the
> *guest's* S2 translation, just like handle_mem_abort() does.
> 
> 	M.
> 

Thanks Marc for taking a look, I'll update to fix these issues and
address the other comments.

-- 
Thanks,
Jack