From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-fw-6001.amazon.com (smtp-fw-6001.amazon.com [52.95.48.154]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D745D21C9E7; Mon, 19 May 2025 21:55:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.95.48.154 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747691713; cv=none; b=PtJMJRX3UZnwMimQse0lzUFArdQNiIiUb4WrdplHMZbZh99lPzXda9YpD3WEbWKvKw14PQmRSlw8JjcvO0z5YbA1MsAzxX/zK85AspcCGQzWP5cNoCakDjUSoEbDdFLNVxKMDGnJ1pm0cYtRfTXXwDdQj57QWa48Tb99bKOjkvQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747691713; c=relaxed/simple; bh=dlKAmhW9zKgVRMeo0heLwBPiru8W62725BeAQY5f1+Y=; h=From:To:CC:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=DKdzdBXJ6dr+emk/W1ddQaF2sqWSTLr4pPNpDpdaNVrDlj8yH5cQryygVzPlhkJTHglYwq+bPuqenq6Zi1qNfLr1bPYvnRJzgTu2A8iAmkCVJX4YBYQYNi9A+4imQd5azEbOYAMhuTG55KbId3we2mW96prXDNAtM4bzPFQ94xM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.de; spf=pass smtp.mailfrom=amazon.de; dkim=pass (2048-bit key) header.d=amazon.de header.i=@amazon.de header.b=C1tywkqN; arc=none smtp.client-ip=52.95.48.154 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.de header.i=@amazon.de header.b="C1tywkqN" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.de; i=@amazon.de; q=dns/txt; s=amazoncorp2; t=1747691713; x=1779227713; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=ZTBWHR+TKfiCZBw1vt8bZJYOmNBojFPZ6w32Ws9zvXo=; b=C1tywkqNYcAu7wEq4u2sp6anECvhWQV9pt1Tn33SIrto04xb9jmfTiUO VaEqKh7JQUuJOJWhhO5CIWQzWJ66MR2GfzD0lSP+KT4Tb5qDkbllSTgWa 64m8EfyN8B/hJ07pF3sEme2zcu8JyRLcfKavWh8qSVIryFmxGsZSRBCfs 3kdF8xlX8Jm4+/fdw2BGvCMoZuC1mcOnL3CDMnTGynqPBZwVHtqG7lISa hLwpVEcC+QavIA253HjyQjz8BKbJtXaLukAnG8Dhc7XqYRzN+kTn5HitY 01u0UeRFbsv9xtzmz3yWJ2YxNXg9BnvoQHIwSKO4f4tOZ0Rmi7qIpOunh w==; X-IronPort-AV: E=Sophos;i="6.15,301,1739836800"; d="scan'208";a="491768678" Received: from iad12-co-svc-p1-lb1-vlan2.amazon.com (HELO smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev) ([10.43.8.2]) by smtp-border-fw-6001.iad6.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 May 2025 21:55:08 +0000 Received: from EX19MTAUWC001.ant.amazon.com [10.0.7.35:27353] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.0.141:2525] with esmtp (Farcaster) id be5f95f2-05c5-4170-ba78-00aac800df84; Mon, 19 May 2025 21:55:07 +0000 (UTC) X-Farcaster-Flow-ID: be5f95f2-05c5-4170-ba78-00aac800df84 Received: from EX19MTAUWA001.ant.amazon.com (10.250.64.204) by EX19MTAUWC001.ant.amazon.com (10.250.64.174) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14; Mon, 19 May 2025 21:55:06 +0000 Received: from email-imr-corp-prod-pdx-all-2c-785684ef.us-west-2.amazon.com (10.25.36.214) by mail-relay.amazon.com (10.250.64.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14 via Frontend Transport; Mon, 19 May 2025 21:55:06 +0000 Received: from dev-dsk-ptyadav-1c-43206220.eu-west-1.amazon.com (dev-dsk-ptyadav-1c-43206220.eu-west-1.amazon.com [172.19.91.144]) by email-imr-corp-prod-pdx-all-2c-785684ef.us-west-2.amazon.com (Postfix) with ESMTP id 17CACA025F; Mon, 19 May 2025 21:55:06 +0000 (UTC) Received: by dev-dsk-ptyadav-1c-43206220.eu-west-1.amazon.com (Postfix, from userid 23027615) id A24E86609; Mon, 19 May 2025 23:55:05 +0200 (CEST) From: Pratyush Yadav To: Mike Rapoport CC: Andrew Morton , Alexandre Ghiti , , , Subject: Re: [PATCH] mm/cma: make detection of highmem_start more robust In-Reply-To: <20250519171805.1288393-1-rppt@kernel.org> References: <20250519171805.1288393-1-rppt@kernel.org> Date: Mon, 19 May 2025 23:55:05 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Hi Mike, On Mon, May 19 2025, Mike Rapoport wrote: > 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. I don't know if they are fine or they haven't realized this is a bug yet. Either way, this patch fixes the crash for me on x86_64, restores how it should behave, and doesn't seem to make anything worse, so: Tested-by: Pratyush Yadav Thanks for fixing this! > > 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); -- Regards, Pratyush Yadav Amazon Web Services Development Center Germany GmbH Tamara-Danz-Str. 13 10243 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B Sitz: Berlin Ust-ID: DE 365 538 597