linux-kernel - [RFC 15/18] pkernfs: register device memory for IOMMU domain pgtables

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Message-ID: <20240205120203.60312-16-jgowans@amazon.com>
Date: Mon, 5 Feb 2024 12:02:00 +0000
From: James Gowans <jgowans@...zon.com>
To: <linux-kernel@...r.kernel.org>
CC: Eric Biederman <ebiederm@...ssion.com>, <kexec@...ts.infradead.org>,
	"Joerg Roedel" <joro@...tes.org>, Will Deacon <will@...nel.org>,
	<iommu@...ts.linux.dev>, Alexander Viro <viro@...iv.linux.org.uk>, "Christian
 Brauner" <brauner@...nel.org>, <linux-fsdevel@...r.kernel.org>, Paolo Bonzini
	<pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>,
	<kvm@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>,
	<linux-mm@...ck.org>, Alexander Graf <graf@...zon.com>, David Woodhouse
	<dwmw@...zon.co.uk>, "Jan H . Schoenherr" <jschoenh@...zon.de>, Usama Arif
	<usama.arif@...edance.com>, Anthony Yznaga <anthony.yznaga@...cle.com>,
	Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>,
	<madvenka@...ux.microsoft.com>, <steven.sistare@...cle.com>,
	<yuleixzhang@...cent.com>
Subject: [RFC 15/18] pkernfs: register device memory for IOMMU domain pgtables

Similarly to the root/context pgtables, the IOMMU driver also does
phys_to_virt when walking the domain pgtables. To make this work
properly the physical memory needs to be mapped in at the correct place
in the direct map. Register a memory device to support this.

The alternative would be to wrap all of the phys_to_virt functions in
something which is pkernfs aware.
---
 fs/pkernfs/iommu.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/pkernfs/iommu.c b/fs/pkernfs/iommu.c
index 5d0b256e7dd8..073b9dd48237 100644
--- a/fs/pkernfs/iommu.c
+++ b/fs/pkernfs/iommu.c
@@ -9,6 +9,7 @@ void pkernfs_get_region_for_ppts(struct file *ppts, struct pkernfs_region *pkern
 	struct pkernfs_inode *pkernfs_inode;
 	unsigned long *mappings_block_vaddr;
 	unsigned long inode_idx;
+	int rc;
 
 	/*
 	 * For a pkernfs region block, the "mappings_block" field is still
@@ -22,7 +23,20 @@ void pkernfs_get_region_for_ppts(struct file *ppts, struct pkernfs_region *pkern
 	mappings_block_vaddr = (unsigned long *)pkernfs_addr_for_block(NULL,
 			pkernfs_inode->mappings_block);
 	set_bit(0, mappings_block_vaddr);
-	pkernfs_region->vaddr = mappings_block_vaddr;
+
+	dev_set_name(&pkernfs_region->dev, "vfio-ppt-%s", pkernfs_inode->filename);
+	rc = device_register(&pkernfs_region->dev);
+	if (rc)
+		pr_err("device_register failed: %i\n", rc);
+
+	pkernfs_region->pgmap.range.start = pkernfs_base +
+		(pkernfs_inode->mappings_block * PMD_SIZE);
+	pkernfs_region->pgmap.range.end =
+		pkernfs_region->pgmap.range.start + PMD_SIZE - 1;
+	pkernfs_region->pgmap.nr_range = 1;
+	pkernfs_region->pgmap.type = MEMORY_DEVICE_GENERIC;
+	pkernfs_region->vaddr =
+		devm_memremap_pages(&pkernfs_region->dev, &pkernfs_region->pgmap);
 	pkernfs_region->paddr = pkernfs_base + (pkernfs_inode->mappings_block * (2 << 20));
 }
 void pkernfs_alloc_iommu_root_pgtables(struct pkernfs_region *pkernfs_region)
-- 
2.40.1