swiotlb cleanups v3
Christoph Hellwig
hch at lst.de
Tue Apr 20 19:23:12 AEST 2021
On Sat, Apr 17, 2021 at 11:39:22AM -0500, Tom Lendacky wrote:
> Somewhere between the 1st and 2nd patch, specifying a specific swiotlb
> for an SEV guest is no longer honored. For example, if I start an SEV
> guest with 16GB of memory and specify swiotlb=131072 I used to get a
> 256MB SWIOTLB. However, after the 2nd patch, the swiotlb=131072 is no
> longer honored and I get a 982MB SWIOTLB (as set via sev_setup_arch() in
> arch/x86/mm/mem_encrypt.c).
>
> I can't be sure which patch caused the issue since an SEV guest fails to
> boot with the 1st patch but can boot with the 2nd patch, at which point
> the SWIOTLB comes in at 982MB (I haven't had a chance to debug it and so
> I'm hoping you might be able to quickly spot what's going on).
Can you try this patch?
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 0a5b6f7e75bce6..ac81ef97df32f5 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -71,15 +71,17 @@ struct io_tlb_mem *io_tlb_default_mem;
*/
static unsigned int max_segment;
-static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
+static unsigned long swiotlb_cmdline_size;
static int __init
setup_io_tlb_npages(char *str)
{
if (isdigit(*str)) {
/* avoid tail segment of size < IO_TLB_SEGSIZE */
- default_nslabs =
- ALIGN(simple_strtoul(str, &str, 0), IO_TLB_SEGSIZE);
+ unsigned long nslabs = simple_strtoul(str, &str, 0);
+
+ swiotlb_cmdline_size =
+ ALIGN(nslabs, IO_TLB_SEGSIZE) << IO_TLB_SHIFT;
}
if (*str == ',')
++str;
@@ -108,7 +110,9 @@ void swiotlb_set_max_segment(unsigned int val)
unsigned long swiotlb_size_or_default(void)
{
- return default_nslabs << IO_TLB_SHIFT;
+ if (swiotlb_cmdline_size)
+ return swiotlb_cmdline_size;
+ return IO_TLB_DEFAULT_SIZE;
}
void __init swiotlb_adjust_size(unsigned long size)
@@ -118,9 +122,10 @@ void __init swiotlb_adjust_size(unsigned long size)
* architectures such as those supporting memory encryption to
* adjust/expand SWIOTLB size for their use.
*/
- size = ALIGN(size, IO_TLB_SIZE);
- default_nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
- pr_info("SWIOTLB bounce buffer size adjusted to %luMB", size >> 20);
+ if (!swiotlb_cmdline_size)
+ swiotlb_cmdline_size = ALIGN(size, IO_TLB_SIZE);
+ pr_info("SWIOTLB bounce buffer size adjusted to %luMB",
+ swiotlb_cmdline_size >> 20);
}
void swiotlb_print_info(void)
@@ -209,7 +214,7 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
void __init
swiotlb_init(int verbose)
{
- size_t bytes = PAGE_ALIGN(default_nslabs << IO_TLB_SHIFT);
+ size_t bytes = PAGE_ALIGN(swiotlb_size_or_default());
void *tlb;
if (swiotlb_force == SWIOTLB_NO_FORCE)
@@ -219,7 +224,7 @@ swiotlb_init(int verbose)
tlb = memblock_alloc_low(bytes, PAGE_SIZE);
if (!tlb)
goto fail;
- if (swiotlb_init_with_tbl(tlb, default_nslabs, verbose))
+ if (swiotlb_init_with_tbl(tlb, bytes >> IO_TLB_SHIFT, verbose))
goto fail_free_mem;
return;
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