linux-kernel - [PATCH RFC 09/10] vfio/type1: Use follow_pfn for VM

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Date:   Fri, 10 Jan 2020 19:03:12 +0000
From:   Joao Martins <joao.m.martins@...cle.com>
To:     linux-nvdimm@...ts.01.org
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>, kvm@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Liran Alon <liran.alon@...cle.com>,
        Nikita Leshenko <nikita.leshchenko@...cle.com>,
        Barret Rhoden <brho@...gle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: [PATCH RFC 09/10] vfio/type1: Use follow_pfn for VM_FPNMAP VMAs

From: Nikita Leshenko <nikita.leshchenko@...cle.com>

Unconditionally interpreting vm_pgoff as a PFN is incorrect.

VMAs created by /dev/mem do this, but in general VM_PFNMAP just means
that the VMA doesn't have an associated struct page and is being managed
directly by something other than the core mmu.

Use follow_pfn like KVM does to find the PFN.

Signed-off-by: Nikita Leshenko <nikita.leshchenko@...cle.com>
---
 drivers/vfio/vfio_iommu_type1.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 2ada8e6cdb88..1e43581f95ea 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -362,9 +362,9 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 	vma = find_vma_intersection(mm, vaddr, vaddr + 1);
 
 	if (vma && vma->vm_flags & VM_PFNMAP) {
-		*pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
-		if (is_invalid_reserved_pfn(*pfn))
-			ret = 0;
+		ret = follow_pfn(vma, vaddr, pfn);
+		if (!ret && !is_invalid_reserved_pfn(*pfn))
+			ret = -EOPNOTSUPP;
 	}
 
 	up_read(&mm->mmap_sem);
-- 
2.17.1