From dfcf2e017f5bb928094952d5d56d3566d3d07ba7 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Tue, 25 Jan 2022 16:20:01 +0300 Subject: [PATCH] swiotlb: do not zero buffer in set_memory_decrypted() For larger TDX VM, memset() after set_memory_decrypted() in swiotlb_update_mem_attributes() takes substantial portion of boot time. Zeroing doesn't serve any functional purpose. Malicious VMM can mess with decrypted/shared buffer at any point. Remove the memset(). Signed-off-by: Kirill A. Shutemov Acked-by: Tom Lendacky Signed-off-by: Christoph Hellwig --- kernel/dma/swiotlb.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index f1e7ea1..9390b38 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -207,8 +207,6 @@ void __init swiotlb_update_mem_attributes(void) mem->vaddr = swiotlb_mem_remap(mem, bytes); if (!mem->vaddr) mem->vaddr = vaddr; - - memset(mem->vaddr, 0, bytes); } static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start, -- 2.7.4