linux-kernel - [RFC] dma-buf: system_heap: add PTE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <3da6a916cd6d489690b05d2bd64a2b3a@honor.com>
Date: Mon, 8 Dec 2025 09:41:27 +0000
From: gao xu <gaoxu2@...or.com>
To: "sumit.semwal@...aro.org" <sumit.semwal@...aro.org>
CC: Benjamin Gaignard <benjamin.gaignard@...labora.com>, Brian Starkey
	<Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>, "\"T.J. Mercier\""
	<tjmercier@...gle.com>, "Christian König"
	<christian.koenig@....com>, "linux-media@...r.kernel.org"
	<linux-media@...r.kernel.org>, "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>, "linaro-mm-sig@...ts.linaro.org"
	<linaro-mm-sig@...ts.linaro.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Barry Song <21cnbao@...il.com>,
	"surenb@...gle.com" <surenb@...gle.com>, zhouxiaolong
	<zhouxiaolong9@...or.com>
Subject: [RFC] dma-buf: system_heap: add PTE_CONT for larger contiguous

commit 04c7adb5871a ("dma-buf: system_heap: use larger contiguous mappings
instead of per-page mmap") facilitates the use of PTE_CONT. The system_heap
allocates pages of order 4 and 8 that meet the alignment requirements for
PTE_CONT. enabling PTE_CONT for larger contiguous mappings.

After applying this patch, TLB misses are reduced by approximately 5% when
opening the camera on Android systems.

Signed-off-by: gao xu <gaoxu2@...or.com>
---
 drivers/dma-buf/heaps/system_heap.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 4c782fe33..103b06f89 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -202,12 +202,16 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
 		unsigned long n = (sg->length >> PAGE_SHIFT) - pgoff;
 		struct page *page = sg_page(sg) + pgoff;
 		unsigned long size = n << PAGE_SHIFT;
+		pgprot_t prot = vma->vm_page_prot;
 
 		if (addr + size > vma->vm_end)
 			size = vma->vm_end - addr;
 
+		if (((addr | size) & ~CONT_PTE_MASK) == 0)
+			prot = __pgprot(pgprot_val(prot) | PTE_CONT);
+
 		ret = remap_pfn_range(vma, addr, page_to_pfn(page),
-				size, vma->vm_page_prot);
+				size, prot);
 		if (ret)
 			return ret;
 
-- 
2.42.0