Hi Marc,
On 5/27/20 9:41 AM, Marc Zyngier wrote:
> Hi Alex,
>
> On 2020-05-12 17:53, Alexandru Elisei wrote:
>> Hi,
>>
>> On 5/12/20 12:17 PM, James Morse wrote:
>>> Hi Alex, Marc,
>>>
>>> (just on this last_vcpu_ran thing...)
>>>
>>> On 11/05/2020 17:38, Alexandru Elisei wrote:
>>>> On 4/22/20 1:00 PM, Marc Zyngier wrote:
>>>>> From: Christoffer Dall <christoffer.dall@xxxxxxx>
>>>>>
>>>>> As we are about to reuse our stage 2 page table manipulation code for
>>>>> shadow stage 2 page tables in the context of nested virtualization, we
>>>>> are going to manage multiple stage 2 page tables for a single VM.
>>>>>
>>>>> This requires some pretty invasive changes to our data structures,
>>>>> which moves the vmid and pgd pointers into a separate structure and
>>>>> change pretty much all of our mmu code to operate on this structure
>>>>> instead.
>>>>>
>>>>> The new structure is called struct kvm_s2_mmu.
>>>>>
>>>>> There is no intended functional change by this patch alone.
>>>>> diff --git a/arch/arm64/include/asm/kvm_host.h
>>>>> b/arch/arm64/include/asm/kvm_host.h
>>>>> index 7dd8fefa6aecd..664a5d92ae9b8 100644
>>>>> --- a/arch/arm64/include/asm/kvm_host.h
>>>>> +++ b/arch/arm64/include/asm/kvm_host.h
>>>>> @@ -63,19 +63,32 @@ struct kvm_vmid {
>>>>> u32 vmid;
>>>>> };
>>>>>
>>>>> -struct kvm_arch {
>>>>> +struct kvm_s2_mmu {
>>>>> struct kvm_vmid vmid;
>>>>>
>>>>> - /* stage2 entry level table */
>>>>> - pgd_t *pgd;
>>>>> - phys_addr_t pgd_phys;
>>>>> -
>>>>> - /* VTCR_EL2 value for this VM */
>>>>> - u64 vtcr;
>>>>> + /*
>>>>> + * stage2 entry level table
>>>>> + *
>>>>> + * Two kvm_s2_mmu structures in the same VM can point to the same pgd
>>>>> + * here. This happens when running a non-VHE guest hypervisor which
>>>>> + * uses the canonical stage 2 page table for both vEL2 and for vEL1/0
>>>>> + * with vHCR_EL2.VM == 0.
>>>> It makes more sense to me to say that a non-VHE guest hypervisor will use the
>>>> canonical stage *1* page table when running at EL2
>>> Can KVM say anything about stage1? Its totally under the the guests control
>>> even at vEL2...
>>
>> It just occurred to me that "canonical stage 2 page table" refers to the L0
>> hypervisor stage 2, not to the L1 hypervisor stage 2. If you don't mind my
>> suggestion, perhaps the comment can be slightly improved to avoid any confusion?
>> Maybe something along the lines of "[..] This happens when running a
>> non-VHE guest
>> hypervisor, in which case we use the canonical stage 2 page table for both vEL2
>> and for vEL1/0 with vHCR_EL2.VM == 0".
>
> If the confusion stems from the lack of guest stage-2, how about:
>
> "This happens when running a guest using a translation regime that isn't
> affected by its own stage-2 translation, such as a non-VHE hypervisor
> running at vEL2, or for vEL1/EL0 with vHCR_EL2.VM == 0. In that case,
> we use the canonical stage-2 page tables."
>
> instead? Does this lift the ambiguity?
Yes, that's perfect.
Thanks,
Alex
>
> Thanks,
>
> M.
