linux-kernel - Re: [PATCH v2 2/5] vfio/type1: optimize vfio_pin_pages

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Message-ID: <8806f687-12e4-4456-a7b6-ecdc5adc9f2e@redhat.com>
Date: Fri, 4 Jul 2025 10:41:41 +0200
From: David Hildenbrand <david@...hat.com>
To: lizhe.67@...edance.com, alex.williamson@...hat.com,
 akpm@...ux-foundation.org, peterx@...hat.com, jgg@...pe.ca
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 2/5] vfio/type1: optimize vfio_pin_pages_remote()


>    * Attempt to pin pages.  We really don't want to track all the pfns and
>    * the iommu can only map chunks of consecutive pfns anyway, so get the
> @@ -680,32 +724,47 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
>   		 * and rsvd here, and therefore continues to use the batch.
>   		 */
>   		while (true) {
> +			long nr_pages, acct_pages = 0;
> +
>   			if (pfn != *pfn_base + pinned ||
>   			    rsvd != is_invalid_reserved_pfn(pfn))
>   				goto out;
>   
> +			/*
> +			 * Using GUP with the FOLL_LONGTERM in
> +			 * vaddr_get_pfns() will not return invalid
> +			 * or reserved pages.
> +			 */
> +			nr_pages = num_pages_contiguous(
> +					&batch->pages[batch->offset],
> +					batch->size);
> +			if (!rsvd) {
> +				acct_pages = nr_pages;
> +				acct_pages -= vpfn_pages(dma, iova, nr_pages);

I'm not familiar with the vpfn_pages() part, but the other stuff LGTM.

-- 
Cheers,

David / dhildenb