Re: [PATCH v2 4/9] KVM: Rework .gmem_invalidate() into .gmem_free_folio()

[Ackerley Tng]

Sean Christopherson <seanjc@xxxxxxxxxx> writes:

> On Mon, Jun 29, 2026, Ackerley Tng wrote:
>> Sean Christopherson <seanjc@xxxxxxxxxx> writes:
>>
>> >
>> > [...snip...]
>> >
>> >
>> > -void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end)
>> > +void sev_gmem_free_folio(struct folio *folio)
>> >  {
>> > +	kvm_pfn_t start = page_to_pfn(folio_page(folio, 0));
>> > +	kvm_pfn_t end = start + (1ul << folio_order(folio));
>> >  	kvm_pfn_t pfn;
>> >
>> >  	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
>>
>> I thought we intended to draw the line such that the platforms don't
>> reference folios, and so this function should be parametrized by pfn.
>>
>> I think we should still stick with
>>
>>   .free_folio = kvm_gmem_free_folio
>>
>> and kvm_gmem_free_folio() translates the folio to pfns and calls the
>> arch function, named something like .gmem_LIFECYCLE_ACTION_pfn_range.
>>
>> Now for LIFECYCLE_ACTION, one way to think of it is that this should
>> represent the point in the lifecycle of guest_memfd memory where the
>> memory is removed from guest's private use, so perhaps "host_reclaim"?
>
> kvm_arch_gmem_reclaim_memory()?  I don't want to include "host", because the
> "reclaim" may or may not be host initiated.  I don't want to use "pfn_range"
> because it's too close to "gfn_range".
>

kvm_arch_gmem_reclaim_memory() is good. It'll take PFNs pfn_start and
pfn_end? If yes, I'll wait for your next revision before I make a v9 for
guest_memfd in-place conversions.

I think Fuad and Suzuki should be good with this too wrt conversions,
based on their responses to [1].

>> Then kvm_gmem_free_folio() becomes:
>>
>>    kvm_gmem_free_folio() {
>>        pfn_start, pfn_end = translate folio to pfn range;
>>        kvm_x86_call(gmem_host_reclaim_pfn_range)(pfn_start, pfn_end);
>>    }
>>
>>
>> And in conversions
>>
>>    if (!to_private) {
>>        pfn_start, pfn_end = translate guest_memfd offset range to pfns;
>>        kvm_x86_call(gmem_host_reclaim_pfn_range)(pfn_start, pfn_end);
>>    }
>>
>> (and now it is right for the !to_private check to remain in guest_memfd
>> since we're explicitly using that to guard a *host* reclaim function.
>>
>>
>> [...snip...]
>>
>>
>> [1] https://lore.kernel.org/all/CAEvNRgGX3GkazCWM=6y9YLgn=YemXuG==Oo+L58cac1Fd86_TQ@xxxxxxxxxxxxxx/
>>
>> >
>> > [...snip...]
>> >