[PATCH 03/12] swiotlb: simplify swiotlb_max_segment

Christoph Hellwig
2022-03-01T10:53:02Z

Remove the bogus Xen override that was usually larger than the actual
size and just calculate the value on demand. Note that
swiotlb_max_segment still doesn't make sense as an interface and should
eventually be removed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
drivers/xen/swiotlb-xen.c | 2 --
include/linux/swiotlb.h | 1 -
kernel/dma/swiotlb.c | 20 +++-----------------
3 files changed, 3 insertions(+), 20 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 47aebd98f52f5..485cd06ed39e7 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -202,7 +202,6 @@ int xen_swiotlb_init(void)
rc = swiotlb_late_init_with_tbl(start, nslabs);
if (rc)
return rc;
- swiotlb_set_max_segment(PAGE_SIZE);
return 0;
error:
if (nslabs > 1024 && repeat--) {
@@ -254,7 +253,6 @@ void __init xen_swiotlb_init_early(void)

if (swiotlb_init_with_tbl(start, nslabs, true))
panic("Cannot allocate SWIOTLB buffer");
- swiotlb_set_max_segment(PAGE_SIZE);
}
#endif /* CONFIG_X86 */

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index f6c3638255d54..9fb3a568f0c51 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -164,7 +164,6 @@ static inline void swiotlb_adjust_size(unsigned long size)
#endif /* CONFIG_SWIOTLB */

extern void swiotlb_print_info(void);
-extern void swiotlb_set_max_segment(unsigned int);

#ifdef CONFIG_DMA_RESTRICTED_POOL
struct page *swiotlb_alloc(struct device *dev, size_t size);
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 64b390136f9ef..e31c235b5fd9e 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -75,12 +75,6 @@ struct io_tlb_mem io_tlb_default_mem;

phys_addr_t swiotlb_unencrypted_base;

-/*
- * Max segment that we can provide which (if pages are contingous) will
- * not be bounced (unless SWIOTLB_FORCE is set).
- */
-static unsigned int max_segment;
-
static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;

static int __init
@@ -104,18 +98,12 @@ early_param("swiotlb", setup_io_tlb_npages);

unsigned int swiotlb_max_segment(void)
{
- return io_tlb_default_mem.nslabs ? max_segment : 0;
+ if (!io_tlb_default_mem.nslabs)
+ return 0;
+ return rounddown(io_tlb_default_mem.nslabs << IO_TLB_SHIFT, PAGE_SIZE);
}
EXPORT_SYMBOL_GPL(swiotlb_max_segment);

-void swiotlb_set_max_segment(unsigned int val)
-{
- if (swiotlb_force = SWIOTLB_FORCE)
- max_segment = 1;
- else
- max_segment = rounddown(val, PAGE_SIZE);
-}
-
unsigned long swiotlb_size_or_default(void)
{
return default_nslabs << IO_TLB_SHIFT;
@@ -267,7 +255,6 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)

if (verbose)
swiotlb_print_info();
- swiotlb_set_max_segment(mem->nslabs << IO_TLB_SHIFT);
return 0;
}

@@ -368,7 +355,6 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
swiotlb_init_io_tlb_mem(mem, virt_to_phys(tlb), nslabs, true);

swiotlb_print_info();
- swiotlb_set_max_segment(mem->nslabs << IO_TLB_SHIFT);
return 0;
}

--
2.30.2