Re: [PATCH v5 00/13] KVM: mm: fd-based approach for supporting KVM guest private memory

[Andy Lutomirski]

On Tue, Apr 5, 2022, at 11:30 AM, Sean Christopherson wrote:
> On Tue, Apr 05, 2022, Andy Lutomirski wrote:

>
>> resume guest
>> *** host -> hypervisor -> guest ***
>> Guest unshares the page.
>> *** guest -> hypervisor ***
>> Hypervisor removes PTE.  TLBI.
>> *** hypervisor -> guest ***
>> 
>> Obviously considerable cleverness is needed to make a virt IOMMU like this
>> work well, but still.
>> 
>> Anyway, my suggestion is that the fd backing proposal get slightly modified
>> to get it ready for multiple subtypes of backing object, which should be a
>> pretty minimal change.  Then, if someone actually needs any of this
>> cleverness, it can be added later.  In the mean time, the
>> pread()/pwrite()/splice() scheme is pretty good.
>
> Tangentially related to getting private-fd ready for multiple things, 
> what about
> implementing the pread()/pwrite()/splice() scheme in pKVM itself?  I.e. 
> read() on
> the VM fd, with the offset corresponding to gfn in some way.
>

Hmm, could make sense.