linux-kernel - [PATCH v3 20/21] vfio_iommu_type1: specify FOLL_HINT_BULK to pin_user

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Date:   Mon,  6 Jun 2022 20:37:24 +0000
From:   Ankur Arora <ankur.a.arora@...cle.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Cc:     torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
        mike.kravetz@...cle.com, mingo@...nel.org, luto@...nel.org,
        tglx@...utronix.de, bp@...en8.de, peterz@...radead.org,
        ak@...ux.intel.com, arnd@...db.de, jgg@...dia.com,
        jon.grimm@....com, boris.ostrovsky@...cle.com,
        konrad.wilk@...cle.com, joao.m.martins@...cle.com,
        ankur.a.arora@...cle.com, alex.williamson@...hat.com
Subject: [PATCH v3 20/21] vfio_iommu_type1: specify FOLL_HINT_BULK to pin_user_pages()

Specify FOLL_HINT_BULK to pin_user_pages_remote() so it is aware
that this pin is part of a larger region being pinned, and can
optimize based on that expectation.

Cc: alex.williamson@...hat.com
Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 drivers/vfio/vfio_iommu_type1.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 9394aa9444c1..138b23769793 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -553,6 +553,9 @@ static int vaddr_get_pfns(struct mm_struct *mm, unsigned long vaddr,
 	if (prot & IOMMU_WRITE)
 		flags |= FOLL_WRITE;
 
+	/* Tell gup that this pin iteration is part of a larger set of pins. */
+	flags |= FOLL_HINT_BULK;
+
 	mmap_read_lock(mm);
 	ret = pin_user_pages_remote(mm, vaddr, npages, flags | FOLL_LONGTERM,
 				    pages, NULL, NULL);
-- 
2.31.1