linux-kernel - Re: [PATCH v3 07/30] kho: add interfaces to unpreserve folios and physical memory ranges

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Message-ID: <20250814170116.GI802098@nvidia.com>
Date: Thu, 14 Aug 2025 14:01:16 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Pasha Tatashin <pasha.tatashin@...een.com>
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Subject: Re: [PATCH v3 07/30] kho: add interfaces to unpreserve folios and
 physical memory ranges

On Thu, Aug 14, 2025 at 03:05:04PM +0000, Pasha Tatashin wrote:
> On Thu, Aug 14, 2025 at 1:22 PM Jason Gunthorpe <jgg@...dia.com> wrote:
> >
> > On Thu, Aug 07, 2025 at 01:44:13AM +0000, Pasha Tatashin wrote:
> > > +int kho_unpreserve_phys(phys_addr_t phys, size_t size)
> > > +{
> >
> > Why are we adding phys apis? Didn't we talk about this before and
> > agree not to expose these?
> 
> It is already there, this patch simply completes a lacking unpreserve part.

This patch yes, but that is because the later patches intend to use
it, which I argue those patches should not.

There should not be any users of these phys interfaces because they
make no sense. The API preserves folios and brings allocated folios
back on the other side. None of that is phys.

> > Which is perhaps another comment, if this __get_free_pages() is going
> > to be a common pattern (and I guess it will be) then the API should be
> > streamlined alot more:
> >
> >  void *kho_alloc_preserved_memory(gfp, size);
> >  void kho_free_preserved_memory(void *);
> 
> Hm, not all GFP flags are compatible with KHO preserve, but we could
> add this or similar API, but first let's make KHO completely
> stateless: remove, finalize and abort parts from it.

Right, in those cases we often warn on and mask invalid flag

Jason