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h=From:To:Cc:Subject:Date:From; b=cLJfzyvOj9LiXyRKKySMpCuRl4rLhZeRKMh/B4RieFAr3l7IP/SyyE7A3To2M5RoN pIQmQLZSE2mLRFehJX0hoVFHGH+sJFmX8U88YnWyOJ+zikB15X1EDNeyJbUoTz56vP AKMg32x88KcZ/STBTQ2Fl2FSrz6WNsnRDE3TEFs1AopcntMaHml0tZcPY+pbV2Inxb cPkUfVwd+W+xUoFeoimp3e4W6TbQVWkOf9Ru5G0ZpIz6aVUNBWj3aX9tNNjuQy5Y4h zZhsGBZKtNex2mk1VY2DFnO5NHyF2KY9h6sWKDmFCG7qHLm99sOAMjfmoR1fjASDhD jw2O9O2mwep6g== From: Mike Rapoport To: Andrew Morton Cc: Alexandre Ghiti , Mike Rapoport , Pratyush Yadav , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] mm/cma: make detection of highmem_start more robust Date: Mon, 19 May 2025 20:18:05 +0300 Message-ID: <20250519171805.1288393-1-rppt@kernel.org> X-Mailer: git-send-email 2.47.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: E2D9940005 X-Stat-Signature: 5cbigupb6ekdqrd39djtdn6ihgd79yye X-HE-Tag: 1747675092-143753 X-HE-Meta: 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 izEawHmK VtArmrsqAESkKcEjVKshcyJg+KynjT2Cw+t6ItWGhr/InMZJCwAxVkvTx9Ia7SBx+HNDup+74gIBYeg8H8JO5fMzleONLZF4kQl95q8nTJbPb5fKekulKIjikJKG+u7FdOb6jk0Pd1M03V1gFZOPqzfbUcBZMAJH40UdLxIZcz6nTvtlrly8y5SN076+9TsOxUg9XD8EqT12Qb1XroWuwB9vHegIgeE08HiksXiiAljbE64llPAPbyw6MOsLpcifeAKj4jJmCS696ct4KgSXIgG28jcK+gkNVawkHfXoZRkpX3YbNF2MKOdaQDbPRB3N7xqWGu4l6+Fxe+EIZwl4qWKFs1Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Mike Rapoport (Microsoft)" Pratyush Yadav reports the following crash: ------------[ cut here ]------------ kernel BUG at arch/x86/mm/physaddr.c:23! ception 0x06 IP 10:ffffffff812ebbf8 error 0 cr2 0xffff88903ffff000 CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc6+ #231 PREEMPT(undef) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014 RIP: 0010:__phys_addr+0x58/0x60 Code: 01 48 89 c2 48 d3 ea 48 85 d2 75 05 e9 91 52 cf 00 0f 0b 48 3d ff ff ff 1f 77 0f 48 8b 05 20 54 55 01 48 01 d0 e9 78 52 cf 00 <0f> 0b 90 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 RSP: 0000:ffffffff82803dd8 EFLAGS: 00010006 ORIG_RAX: 0000000000000000 RAX: 000000007fffffff RBX: 00000000ffffffff RCX: 0000000000000000 RDX: 000000007fffffff RSI: 0000000280000000 RDI: ffffffffffffffff RBP: ffffffff82803e68 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff83153180 R11: ffffffff82803e48 R12: ffffffff83c9aed0 R13: 0000000000000000 R14: 0000001040000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:0000000000000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff88903ffff000 CR3: 0000000002838000 CR4: 00000000000000b0 Call Trace: ? __cma_declare_contiguous_nid+0x6e/0x340 ? cma_declare_contiguous_nid+0x33/0x70 ? dma_contiguous_reserve_area+0x2f/0x70 ? setup_arch+0x6f1/0x870 ? start_kernel+0x52/0x4b0 ? x86_64_start_reservations+0x29/0x30 ? x86_64_start_kernel+0x7c/0x80 ? common_startup_64+0x13e/0x141 The reason is that __cma_declare_contiguous_nid() does: highmem_start = __pa(high_memory - 1) + 1; If dma_contiguous_reserve_area() (or any other CMA declaration) is called before free_area_init(), high_memory is uninitialized. Without CONFIG_DEBUG_VIRTUAL, it will likely work but use the wrong value for highmem_start. The issue occurs because commit e120d1bc12da ("arch, mm: set high_memory in free_area_init()") moved initialization of high_memory after the call to dma_contiguous_reserve() -> __cma_declare_contiguous_nid() on several architectures. In the case CONFIG_HIGHMEM is enabled, some architectures that actually support HIGHMEM (arm, powerpc and x86) have initialization of high_memory before a possible call to __cma_declare_contiguous_nid() and some initialized high_memory late anyway (arc, csky, microblase, mips, sparc, xtensa) even before the commit e120d1bc12da so they are fine with using uninitialized value of high_memory. And in the case CONFIG_HIGHMEM is disabled high_memory essentially becomes the first address after memory end, so instead of relying on high_memory to calculate highmem_start use memblock_end_of_DRAM() and eliminate the dependency of CMA area creation on high_memory in majority of configurations. Reported-by: Pratyush Yadav Tested-by: Alexandre Ghiti Signed-off-by: Mike Rapoport (Microsoft) --- mm/cma.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/cma.c b/mm/cma.c index 15632939f20a..c04be488b099 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -608,7 +608,10 @@ static int __init __cma_declare_contiguous_nid(phys_addr_t *basep, * complain. Find the boundary by adding one to the last valid * address. */ - highmem_start = __pa(high_memory - 1) + 1; + if (IS_ENABLED(CONFIG_HIGHMEM)) + highmem_start = __pa(high_memory - 1) + 1; + else + highmem_start = memblock_end_of_DRAM(); pr_debug("%s(size %pa, base %pa, limit %pa alignment %pa)\n", __func__, &size, &base, &limit, &alignment); -- 2.47.2