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swiotlb: Export swiotlb_max_segment to users

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So they can figure out what is the optimal number of pages
that can be contingously stitched together without fear of
bounce buffer.

We also expose an mechanism for sub-users of SWIOTLB API, such
as Xen-SWIOTLB to set the max segment value. And lastly
if swiotlb=force is set (which mandates we bounce buffer everything)
we set max_segment so at least we can bounce buffer one 4K page
instead of a giant 512KB one for which we may not have space.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reported-and-Tested-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2016-12-20 10:02:02 -05:00 committed by Konrad Rzeszutek Wilk
parent fff5d99225
commit 7453c549f5
4 changed files with 34 additions and 10 deletions
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11
drivers/gpu/drm/i915/i915_gem.c
View file

@ -2290,15 +2290,6 @@ void __i915_gem_object_put_pages(struct drm_i915_gem_object *obj,
mutex_unlock(&obj->mm.lock);
}
static unsigned int swiotlb_max_size(void)
{
#if IS_ENABLED(CONFIG_SWIOTLB)
return rounddown(swiotlb_nr_tbl() << IO_TLB_SHIFT, PAGE_SIZE);
#else
return 0;
#endif
}
static void i915_sg_trim(struct sg_table *orig_st)
{
struct sg_table new_st;
@ -2345,7 +2336,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
GEM_BUG_ON(obj->base.read_domains & I915_GEM_GPU_DOMAINS);
GEM_BUG_ON(obj->base.write_domain & I915_GEM_GPU_DOMAINS);
max_segment = swiotlb_max_size();
max_segment = swiotlb_max_segment();
if (!max_segment)
max_segment = rounddown(UINT_MAX, PAGE_SIZE);

4
drivers/xen/swiotlb-xen.c
View file

@ -275,6 +275,10 @@ int __ref xen_swiotlb_init(int verbose, bool early)
rc = 0;
} else
rc = swiotlb_late_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs);
if (!rc)
swiotlb_set_max_segment(PAGE_SIZE);
return rc;
error:
if (repeat--) {

3
include/linux/swiotlb.h
View file

@ -114,11 +114,14 @@ swiotlb_dma_supported(struct device *hwdev, u64 mask);
#ifdef CONFIG_SWIOTLB
extern void __init swiotlb_free(void);
unsigned int swiotlb_max_segment(void);
#else
static inline void swiotlb_free(void) { }
static inline unsigned int swiotlb_max_segment(void) { return 0; }
#endif
extern void swiotlb_print_info(void);
extern int is_swiotlb_buffer(phys_addr_t paddr);
extern void swiotlb_set_max_segment(unsigned int);
#endif /* __LINUX_SWIOTLB_H */

26
lib/swiotlb.c
View file

@ -82,6 +82,12 @@ static phys_addr_t io_tlb_overflow_buffer;
static unsigned int *io_tlb_list;
static unsigned int io_tlb_index;
/*
* Max segment that we can provide which (if pages are contingous) will
* not be bounced (unless SWIOTLB_FORCE is set).
*/
unsigned int max_segment;
/*
* We need to save away the original address corresponding to a mapped entry
* for the sync operations.
@ -124,6 +130,20 @@ unsigned long swiotlb_nr_tbl(void)
}
EXPORT_SYMBOL_GPL(swiotlb_nr_tbl);
unsigned int swiotlb_max_segment(void)
{
return max_segment;
}
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);
}
/* default to 64MB */
#define IO_TLB_DEFAULT_SIZE (64UL<<20)
unsigned long swiotlb_size_or_default(void)
@ -205,6 +225,7 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
if (verbose)
swiotlb_print_info();
swiotlb_set_max_segment(io_tlb_nslabs << IO_TLB_SHIFT);
return 0;
}
@ -283,6 +304,7 @@ swiotlb_late_init_with_default_size(size_t default_size)
rc = swiotlb_late_init_with_tbl(vstart, io_tlb_nslabs);
if (rc)
free_pages((unsigned long)vstart, order);
return rc;
}
@ -337,6 +359,8 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
late_alloc = 1;
swiotlb_set_max_segment(io_tlb_nslabs << IO_TLB_SHIFT);
return 0;
cleanup4:
@ -351,6 +375,7 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
io_tlb_end = 0;
io_tlb_start = 0;
io_tlb_nslabs = 0;
max_segment = 0;
return -ENOMEM;
}
@ -379,6 +404,7 @@ void __init swiotlb_free(void)
PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
}
io_tlb_nslabs = 0;
max_segment = 0;
}
int is_swiotlb_buffer(phys_addr_t paddr)