From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx> Hyper-V Isolation VM and AMD SEV VM uses swiotlb bounce buffer to share memory with hypervisor. Current swiotlb bounce buffer is only allocated from 0 to ARCH_LOW_ADDRESS_LIMIT which is default to 0xffffffffUL. Isolation VM and AMD SEV VM needs 1G bounce buffer at most. This will fail when there is not enough contiguous memory from 0 to 4G address space and devices also may use memory above 4G address space as DMA memory. Expose swiotlb_alloc_from_low_pages and platform mey set it to false when it's not necessary to limit bounce buffer from 0 to 4G memory. Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx> --- include/linux/swiotlb.h | 1 + kernel/dma/swiotlb.c | 13 +++++++++++-- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index f6c3638255d5..55c178e8eee0 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -191,5 +191,6 @@ static inline bool is_swiotlb_for_alloc(struct device *dev) #endif /* CONFIG_DMA_RESTRICTED_POOL */ extern phys_addr_t swiotlb_unencrypted_base; +extern bool swiotlb_alloc_from_low_pages; #endif /* __LINUX_SWIOTLB_H */ diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index f1e7ea160b43..159fef80f3db 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -73,6 +73,12 @@ enum swiotlb_force swiotlb_force; struct io_tlb_mem io_tlb_default_mem; +/* + * Get IO TLB memory from the low pages if swiotlb_alloc_from_low_pages + * is set. + */ +bool swiotlb_alloc_from_low_pages = true; + phys_addr_t swiotlb_unencrypted_base; /* @@ -284,8 +290,11 @@ swiotlb_init(int verbose) if (swiotlb_force == SWIOTLB_NO_FORCE) return; - /* Get IO TLB memory from the low pages */ - tlb = memblock_alloc_low(bytes, PAGE_SIZE); + if (swiotlb_alloc_from_low_pages) + tlb = memblock_alloc_low(bytes, PAGE_SIZE); + else + tlb = memblock_alloc(bytes, PAGE_SIZE); + if (!tlb) goto fail; if (swiotlb_init_with_tbl(tlb, default_nslabs, verbose)) -- 2.25.1
