Commit 8d58aa48 authored by Alexey Kardashevskiy's avatar Alexey Kardashevskiy Committed by Christoph Hellwig

swiotlb: reduce the swiotlb buffer size on allocation failure

At the moment the AMD encrypted platform reserves 6% of RAM for SWIOTLB
or 1GB, whichever is less. However it is possible that there is no block
big enough in the low memory which make SWIOTLB allocation fail and
the kernel continues without DMA. In such case a VM hangs on DMA.

This moves alloc+remap to a helper and calls it from a loop where
the size is halved on each iteration.

This updates default_nslabs on successful allocation which looks like
an oversight as not doing so should have broken callers of
swiotlb_size_or_default().
Signed-off-by: default avatarAlexey Kardashevskiy <aik@amd.com>
Reviewed-by: default avatarPankaj Gupta <pankaj.gupta@amd.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 30a0b95b
...@@ -300,6 +300,37 @@ static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start, ...@@ -300,6 +300,37 @@ static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
return; return;
} }
static void *swiotlb_memblock_alloc(unsigned long nslabs, unsigned int flags,
int (*remap)(void *tlb, unsigned long nslabs))
{
size_t bytes = PAGE_ALIGN(nslabs << IO_TLB_SHIFT);
void *tlb;
/*
* By default allocate the bounce buffer memory from low memory, but
* allow to pick a location everywhere for hypervisors with guest
* memory encryption.
*/
if (flags & SWIOTLB_ANY)
tlb = memblock_alloc(bytes, PAGE_SIZE);
else
tlb = memblock_alloc_low(bytes, PAGE_SIZE);
if (!tlb) {
pr_warn("%s: Failed to allocate %zu bytes tlb structure\n",
__func__, bytes);
return NULL;
}
if (remap && remap(tlb, nslabs) < 0) {
memblock_free(tlb, PAGE_ALIGN(bytes));
pr_warn("%s: Failed to remap %zu bytes\n", __func__, bytes);
return NULL;
}
return tlb;
}
/* /*
* Statically reserve bounce buffer space and initialize bounce buffer data * Statically reserve bounce buffer space and initialize bounce buffer data
* structures for the software IO TLB used to implement the DMA API. * structures for the software IO TLB used to implement the DMA API.
...@@ -310,7 +341,6 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags, ...@@ -310,7 +341,6 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
struct io_tlb_mem *mem = &io_tlb_default_mem; struct io_tlb_mem *mem = &io_tlb_default_mem;
unsigned long nslabs; unsigned long nslabs;
size_t alloc_size; size_t alloc_size;
size_t bytes;
void *tlb; void *tlb;
if (!addressing_limit && !swiotlb_force_bounce) if (!addressing_limit && !swiotlb_force_bounce)
...@@ -326,31 +356,16 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags, ...@@ -326,31 +356,16 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
swiotlb_adjust_nareas(num_possible_cpus()); swiotlb_adjust_nareas(num_possible_cpus());
nslabs = default_nslabs; nslabs = default_nslabs;
/* while ((tlb = swiotlb_memblock_alloc(nslabs, flags, remap)) == NULL) {
* By default allocate the bounce buffer memory from low memory, but if (nslabs <= IO_TLB_MIN_SLABS)
* allow to pick a location everywhere for hypervisors with guest
* memory encryption.
*/
retry:
bytes = PAGE_ALIGN(nslabs << IO_TLB_SHIFT);
if (flags & SWIOTLB_ANY)
tlb = memblock_alloc(bytes, PAGE_SIZE);
else
tlb = memblock_alloc_low(bytes, PAGE_SIZE);
if (!tlb) {
pr_warn("%s: failed to allocate tlb structure\n", __func__);
return; return;
}
if (remap && remap(tlb, nslabs) < 0) {
memblock_free(tlb, PAGE_ALIGN(bytes));
nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE); nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE);
if (nslabs >= IO_TLB_MIN_SLABS) }
goto retry;
pr_warn("%s: Failed to remap %zu bytes\n", __func__, bytes); if (default_nslabs != nslabs) {
return; pr_info("SWIOTLB bounce buffer size adjusted %lu -> %lu slabs",
default_nslabs, nslabs);
default_nslabs = nslabs;
} }
alloc_size = PAGE_ALIGN(array_size(sizeof(*mem->slots), nslabs)); alloc_size = PAGE_ALIGN(array_size(sizeof(*mem->slots), nslabs));
......
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