linux-kernel - [PATCH RFCv1 13/14] iommufd: Add mmap infrastructure

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Message-ID: <6fef9ff9944381d51dd18f83ec03785a26754dcf.1712978213.git.nicolinc@nvidia.com>
Date: Fri, 12 Apr 2024 20:47:10 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: <will@...nel.org>, <robin.murphy@....com>, <jgg@...dia.com>,
	<kevin.tian@...el.com>, <suravee.suthikulpanit@....com>
CC: <joro@...tes.org>, <linux-kernel@...r.kernel.org>,
	<iommu@...ts.linux.dev>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-tegra@...r.kernel.org>, <yi.l.liu@...el.com>, <eric.auger@...hat.com>,
	<vasant.hegde@....com>, <jon.grimm@....com>, <santosh.shukla@....com>,
	<Dhaval.Giani@....com>, <shameerali.kolothum.thodi@...wei.com>
Subject: [PATCH RFCv1 13/14] iommufd: Add mmap infrastructure

Add for sharing the kernel page with user space. This allows to pass
through HW resource (VCMDQ MMIO pages for example) to user space VMM
and guest OS. Use vma->vm_pgoff as the carrier of a viommu_id.

Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 drivers/iommu/iommufd/main.c | 40 ++++++++++++++++++++++++++++++++++++
 include/linux/iommufd.h      |  4 ++++
 2 files changed, 44 insertions(+)

diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 96ef81530809..5b401c80cca8 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -16,6 +16,7 @@
 #include <linux/mutex.h>
 #include <linux/bug.h>
 #include <uapi/linux/iommufd.h>
+#include <linux/iommu.h>
 #include <linux/iommufd.h>
 
 #include "io_pagetable.h"
@@ -427,11 +428,50 @@ static long iommufd_fops_ioctl(struct file *filp, unsigned int cmd,
 	return ret;
 }
 
+static int iommufd_fops_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct iommufd_ctx *ictx = filp->private_data;
+	size_t size = vma->vm_end - vma->vm_start;
+	u32 viommu_id = (u32)vma->vm_pgoff;
+	struct iommufd_viommu *viommu;
+	unsigned long pfn;
+	int rc;
+
+	if (size > PAGE_SIZE)
+		return -EINVAL;
+
+	viommu = container_of(iommufd_get_object(ictx, viommu_id,
+						 IOMMUFD_OBJ_VIOMMU),
+			      struct iommufd_viommu, obj);
+	if (IS_ERR(viommu))
+		return PTR_ERR(viommu);
+
+	if (!viommu->ops->get_mmap_pfn) {
+		rc = -EOPNOTSUPP;
+		goto out_put_viommu;
+	}
+
+	pfn = viommu->ops->get_mmap_pfn(viommu, size);
+	if (!pfn) {
+		rc = -ENOMEM;
+		goto out_put_viommu;
+	}
+
+	vma->vm_pgoff = 0;
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
+	rc = remap_pfn_range(vma, vma->vm_start, pfn, size, vma->vm_page_prot);
+out_put_viommu:
+	iommufd_put_object(ictx, &viommu->obj);
+	return rc;
+}
+
 static const struct file_operations iommufd_fops = {
 	.owner = THIS_MODULE,
 	.open = iommufd_fops_open,
 	.release = iommufd_fops_release,
 	.unlocked_ioctl = iommufd_fops_ioctl,
+	.mmap = iommufd_fops_mmap,
 };
 
 /**
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 707b6d4b20a3..4a9c6b281d35 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -104,6 +104,8 @@ struct iommufd_viommu {
  *                the include/uapi/linux/iommufd.h header.
  * @vqueue_free: Free all driver-specific parts of an iommufd_vqueue. The memory
  *               of the iommufd_vqueue will be free-ed by iommufd core
+ * @get_mmap_pfn: Return the PFN of a viommu given a finite size, for user space
+ *                to mmap the page(s).
  */
 struct iommufd_viommu_ops {
 	void (*free)(struct iommufd_viommu *viommu);
@@ -114,6 +116,8 @@ struct iommufd_viommu_ops {
 		struct iommufd_viommu *viommu,
 		const struct iommu_user_data *user_data);
 	void (*vqueue_free)(struct iommufd_vqueue *vqueue);
+	unsigned long (*get_mmap_pfn)(struct iommufd_viommu *viommu,
+				      size_t pgsize);
 };
 
 struct iommufd_vqueue {
-- 
2.43.0