linux-kernel - Re: [PATCH v3] vfio/type1: optimize vfio_pin_pages

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Message-ID: <aCy1AzYFyo4Ma1Z1@x1.local>
Date: Tue, 20 May 2025 12:59:47 -0400
From: Peter Xu <peterx@...hat.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: lizhe.67@...edance.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, muchun.song@...ux.dev,
	David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH v3] vfio/type1: optimize vfio_pin_pages_remote() for huge
 folio

Hi, Alex,

On Tue, May 20, 2025 at 08:07:19AM -0600, Alex Williamson wrote:
> Peter, David, if you wouldn't mind double checking the folio usage
> here, I'd appreciate it.  The underlying assumption used here is that
> folios always have physically contiguous pages, so we can increment at
> the remainder of the folio_nr_pages() rather than iterate each page.

Yes I think so.  E.g., there's comment above folio definition too:

/**
 * struct folio - Represents a contiguous set of bytes.
 * ...
 * A folio is a physically, virtually and logically contiguous set
 * of bytes...
 */

For 1G, I wonder if in the future vfio can also use memfd_pin_folios()
internally when possible, e.g. after stumbled on top of a hugetlb folio
when filling the batch.

Thanks,

-- 
Peter Xu