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Message-Id: <7a92817b18ce0e1bd38967784f53bf76a43cb886.1690871004.git.petr.tesarik.ext@huawei.com>
Date: Tue, 1 Aug 2023 08:23:58 +0200
From: Petr Tesarik <petrtesarik@...weicloud.com>
To: Stefano Stabellini <sstabellini@...nel.org>,
Russell King <linux@...linux.org.uk>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
"H. Peter Anvin" <hpa@...or.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Juergen Gross <jgross@...e.com>,
Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
Christoph Hellwig <hch@....de>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Robin Murphy <robin.murphy@....com>,
Christoph Lameter <cl@...ux.com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Vlastimil Babka <vbabka@...e.cz>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Hyeonggon Yoo <42.hyeyoo@...il.com>,
Petr Tesarik <petr.tesarik.ext@...wei.com>,
Jonathan Corbet <corbet@....net>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Hans de Goede <hdegoede@...hat.com>,
James Seo <james@...iv.tech>,
James Clark <james.clark@....com>,
Kees Cook <keescook@...omium.org>,
xen-devel@...ts.xenproject.org (moderated list:XEN HYPERVISOR ARM),
linux-arm-kernel@...ts.infradead.org (moderated list:ARM PORT),
linux-kernel@...r.kernel.org (open list),
linux-mips@...r.kernel.org (open list:MIPS),
iommu@...ts.linux.dev (open list:XEN SWIOTLB SUBSYSTEM),
linux-mm@...ck.org (open list:SLAB ALLOCATOR)
Cc: Roberto Sassu <roberto.sassu@...weicloud.com>, petr@...arici.cz
Subject: [PATCH v7 3/9] swiotlb: add documentation and rename swiotlb_do_find_slots()
From: Petr Tesarik <petr.tesarik.ext@...wei.com>
Add some kernel-doc comments and move the existing documentation of struct
io_tlb_slot to its correct location. The latter was forgotten in commit
942a8186eb445 ("swiotlb: move struct io_tlb_slot to swiotlb.c").
Use the opportunity to give swiotlb_do_find_slots() a more descriptive name
and make it clear how it differs from swiotlb_find_slots().
Signed-off-by: Petr Tesarik <petr.tesarik.ext@...wei.com>
---
include/linux/swiotlb.h | 15 +++++++---
kernel/dma/swiotlb.c | 61 +++++++++++++++++++++++++++++++++++++----
2 files changed, 66 insertions(+), 10 deletions(-)
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 2d453b3e7771..31625ae507ea 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -76,10 +76,6 @@ dma_addr_t swiotlb_map(struct device *dev, phys_addr_t phys,
* @nslabs: The number of IO TLB blocks (in groups of 64) between @start and
* @end. For default swiotlb, this is command line adjustable via
* setup_io_tlb_npages.
- * @list: The free list describing the number of free entries available
- * from each index.
- * @orig_addr: The original address corresponding to a mapped entry.
- * @alloc_size: Size of the allocated buffer.
* @debugfs: The dentry to debugfs.
* @late_alloc: %true if allocated using the page allocator
* @force_bounce: %true if swiotlb bouncing is forced
@@ -111,6 +107,17 @@ struct io_tlb_mem {
#endif
};
+/**
+ * is_swiotlb_buffer() - check if a physical address belongs to a swiotlb
+ * @dev: Device which has mapped the buffer.
+ * @paddr: Physical address within the DMA buffer.
+ *
+ * Check if @paddr points into a bounce buffer.
+ *
+ * Return:
+ * * %true if @paddr points into a bounce buffer
+ * * %false otherwise
+ */
static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
{
struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 0840bc15fb53..66793b59c290 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -62,6 +62,13 @@
#define INVALID_PHYS_ADDR (~(phys_addr_t)0)
+/**
+ * struct io_tlb_slot - IO TLB slot descriptor
+ * @orig_addr: The original address corresponding to a mapped entry.
+ * @alloc_size: Size of the allocated buffer.
+ * @list: The free list describing the number of free entries available
+ * from each index.
+ */
struct io_tlb_slot {
phys_addr_t orig_addr;
size_t alloc_size;
@@ -635,11 +642,22 @@ static void dec_used(struct io_tlb_mem *mem, unsigned int nslots)
}
#endif /* CONFIG_DEBUG_FS */
-/*
- * Find a suitable number of IO TLB entries size that will fit this request and
- * allocate a buffer from that IO TLB pool.
+/**
+ * swiotlb_area_find_slots() - search for slots in one IO TLB memory area
+ * @dev: Device which maps the buffer.
+ * @area_index: Index of the IO TLB memory area to be searched.
+ * @orig_addr: Original (non-bounced) IO buffer address.
+ * @alloc_size: Total requested size of the bounce buffer,
+ * including initial alignment padding.
+ * @alloc_align_mask: Required alignment of the allocated buffer.
+ *
+ * Find a suitable sequence of IO TLB entries for the request and allocate
+ * a buffer from the given IO TLB memory area.
+ * This function takes care of locking.
+ *
+ * Return: Index of the first allocated slot, or -1 on error.
*/
-static int swiotlb_do_find_slots(struct device *dev, int area_index,
+static int swiotlb_area_find_slots(struct device *dev, int area_index,
phys_addr_t orig_addr, size_t alloc_size,
unsigned int alloc_align_mask)
{
@@ -734,6 +752,19 @@ static int swiotlb_do_find_slots(struct device *dev, int area_index,
return slot_index;
}
+/**
+ * swiotlb_find_slots() - search for slots in the whole swiotlb
+ * @dev: Device which maps the buffer.
+ * @orig_addr: Original (non-bounced) IO buffer address.
+ * @alloc_size: Total requested size of the bounce buffer,
+ * including initial alignment padding.
+ * @alloc_align_mask: Required alignment of the allocated buffer.
+ *
+ * Search through the whole software IO TLB to find a sequence of slots that
+ * match the allocation constraints.
+ *
+ * Return: Index of the first allocated slot, or -1 on error.
+ */
static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
size_t alloc_size, unsigned int alloc_align_mask)
{
@@ -742,8 +773,8 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
int i = start, index;
do {
- index = swiotlb_do_find_slots(dev, i, orig_addr, alloc_size,
- alloc_align_mask);
+ index = swiotlb_area_find_slots(dev, i, orig_addr, alloc_size,
+ alloc_align_mask);
if (index >= 0)
return index;
if (++i >= mem->nareas)
@@ -755,6 +786,15 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
#ifdef CONFIG_DEBUG_FS
+/**
+ * mem_used() - get number of used slots in an allocator
+ * @mem: Software IO TLB allocator.
+ *
+ * The result is accurate in this version of the function, because an atomic
+ * counter is available if CONFIG_DEBUG_FS is set.
+ *
+ * Return: Number of used slots.
+ */
static unsigned long mem_used(struct io_tlb_mem *mem)
{
return atomic_long_read(&mem->total_used);
@@ -762,6 +802,15 @@ static unsigned long mem_used(struct io_tlb_mem *mem)
#else /* !CONFIG_DEBUG_FS */
+/**
+ * mem_used() - get number of used slots in an allocator
+ * @mem: Software IO TLB allocator.
+ *
+ * The result is not accurate, because there is no locking of individual
+ * areas.
+ *
+ * Return: Approximate number of used slots.
+ */
static unsigned long mem_used(struct io_tlb_mem *mem)
{
int i;
--
2.25.1
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