mm: add mmap_action_simple_ioremap()

Currently drivers use vm_iomap_memory() as a simple helper function for
I/O remapping memory over a range starting at a specified physical address
over a specified length.

In order to utilise this from mmap_prepare, separate out the core logic
into __simple_ioremap_prep(), update vm_iomap_memory() to use it, and add
simple_ioremap_prepare() to do the same with a VMA descriptor object.

We also add MMAP_SIMPLE_IO_REMAP and relevant fields to the struct
mmap_action type to permit this operation also.

We use mmap_action_ioremap() to set up the actual I/O remap operation once
we have checked and figured out the parameters, which makes
simple_ioremap_prepare() easy to implement.

We then add mmap_action_simple_ioremap() to allow drivers to make use of
this mode.

We update the mmap_prepare documentation to describe this mode.  Finally,
we update the VMA tests to reflect this change.

Link: https://lkml.kernel.org/r/a08ef1c4542202684da63bb37f459d5dbbeddd91.1774045440.git.ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bodo Stroesser <bostroesser@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: David Hildenbrand <david@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Long Li <longli@microsoft.com>
Cc: Marc Dionne <marc.dionne@auristor.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Richard Weinberger <richard@nod.at>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 28 insertions, 2 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 81fbcfed44dd..53b21de40f87 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4321,11 +4321,33 @@ static inline void mmap_action_ioremap(struct vm_area_desc *desc,
  * @start_pfn: The first PFN in the range to remap.
  */
 static inline void mmap_action_ioremap_full(struct vm_area_desc *desc,
-					  unsigned long start_pfn)
+					    unsigned long start_pfn)
 {
 	mmap_action_ioremap(desc, desc->start, start_pfn, vma_desc_size(desc));
 }
 
+/**
+ * mmap_action_simple_ioremap - helper for mmap_prepare hook to specify that the
+ * physical range in [start_phys_addr, start_phys_addr + size) should be I/O
+ * remapped.
+ * @desc: The VMA descriptor for the VMA requiring remap.
+ * @start_phys_addr: Start of the physical memory to be mapped.
+ * @size: Size of the area to map.
+ *
+ * NOTE: Some drivers might want to tweak desc->page_prot for purposes of
+ * write-combine or similar.
+ */
+static inline void mmap_action_simple_ioremap(struct vm_area_desc *desc,
+					      phys_addr_t start_phys_addr,
+					      unsigned long size)
+{
+	struct mmap_action *action = &desc->action;
+
+	action->simple_ioremap.start_phys_addr = start_phys_addr;
+	action->simple_ioremap.size = size;
+	action->type = MMAP_SIMPLE_IO_REMAP;
+}
+
 int mmap_action_prepare(struct vm_area_desc *desc);
 int mmap_action_complete(struct vm_area_struct *vma,
 			 struct mmap_action *action);
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 38fe6b915024..91a3db174d78 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -814,6 +814,7 @@ enum mmap_action_type {
 	MMAP_NOTHING,		/* Mapping is complete, no further action. */
 	MMAP_REMAP_PFN,		/* Remap PFN range. */
 	MMAP_IO_REMAP_PFN,	/* I/O remap PFN range. */
+	MMAP_SIMPLE_IO_REMAP,	/* I/O remap with guardrails. */
 };
 
 /*
@@ -822,13 +823,16 @@ enum mmap_action_type {
  */
 struct mmap_action {
 	union {
-		/* Remap range. */
 		struct {
 			unsigned long start;
 			unsigned long start_pfn;
 			unsigned long size;
 			pgprot_t pgprot;
 		} remap;
+		struct {
+			phys_addr_t start_phys_addr;
+			unsigned long size;
+		} simple_ioremap;
 	};
 	enum mmap_action_type type;