This is a note to let you know that I've just added the patch titled

x86/efi-bgrt: Replace early_memremap() with memremap()

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-efi-bgrt-replace-early_memremap-with-memremap.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From e2c90dd7e11e3025b46719a79fb4bb1e7a5cef9f Mon Sep 17 00:00:00 2001

From: Matt Fleming matt@codeblueprint.co.uk Date: Mon, 21 Dec 2015 14:12:52 +0000 Subject: x86/efi-bgrt: Replace early_memremap() with memremap() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

From: Matt Fleming matt@codeblueprint.co.uk

commit e2c90dd7e11e3025b46719a79fb4bb1e7a5cef9f upstream.

Môshe reported the following warning triggered on his machine since commit 50a0cb565246 ("x86/efi-bgrt: Fix kernel panic when mapping BGRT data"),

[ 0.026936] ------------[ cut here ]------------ [ 0.026941] WARNING: CPU: 0 PID: 0 at mm/early_ioremap.c:137 __early_ioremap+0x102/0x1bb() [ 0.026941] Modules linked in: [ 0.026944] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.0-rc1 #2 [ 0.026945] Hardware name: Dell Inc. XPS 13 9343/09K8G1, BIOS A05 07/14/2015 [ 0.026946] 0000000000000000 900f03d5a116524d ffffffff81c03e60 ffffffff813a3fff [ 0.026948] 0000000000000000 ffffffff81c03e98 ffffffff810a0852 00000000d7b76000 [ 0.026949] 0000000000000000 0000000000000001 0000000000000001 000000000000017c [ 0.026951] Call Trace: [ 0.026955] [<ffffffff813a3fff>] dump_stack+0x44/0x55 [ 0.026958] [<ffffffff810a0852>] warn_slowpath_common+0x82/0xc0 [ 0.026959] [<ffffffff810a099a>] warn_slowpath_null+0x1a/0x20 [ 0.026961] [<ffffffff81d8c395>] __early_ioremap+0x102/0x1bb [ 0.026962] [<ffffffff81d8c602>] early_memremap+0x13/0x15 [ 0.026964] [<ffffffff81d78361>] efi_bgrt_init+0x162/0x1ad [ 0.026966] [<ffffffff81d778ec>] efi_late_init+0x9/0xb [ 0.026968] [<ffffffff81d58ff5>] start_kernel+0x46f/0x49f [ 0.026970] [<ffffffff81d58120>] ? early_idt_handler_array+0x120/0x120 [ 0.026972] [<ffffffff81d58339>] x86_64_start_reservations+0x2a/0x2c [ 0.026974] [<ffffffff81d58485>] x86_64_start_kernel+0x14a/0x16d [ 0.026977] ---[ end trace f9b3812eb8e24c58 ]--- [ 0.026978] efi_bgrt: Ignoring BGRT: failed to map image memory

early_memremap() has an upper limit on the size of mapping it can handle which is ~200KB. Clearly the BGRT image on Môshe's machine is much larger than that.

There's actually no reason to restrict ourselves to using the early_* version of memremap() - the ACPI BGRT driver is invoked late enough in boot that we can use the standard version, with the benefit that the late version allows mappings of arbitrary size.

Reported-by: Môshe van der Sterre me@moshe.nl Tested-by: Môshe van der Sterre me@moshe.nl Signed-off-by: Matt Fleming matt@codeblueprint.co.uk Cc: Josh Triplett josh@joshtriplett.org Cc: Sai Praneeth Prakhya sai.praneeth.prakhya@intel.com Cc: Borislav Petkov bp@suse.de Link: http://lkml.kernel.org/r/1450707172-12561-1-git-send-email-matt@codeblueprin... Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: "Ghannam, Yazen" Yazen.Ghannam@amd.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/platform/efi/efi-bgrt.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/x86/platform/efi/efi-bgrt.c +++ b/arch/x86/platform/efi/efi-bgrt.c @@ -69,14 +69,14 @@ void __init efi_bgrt_init(void) return; }

- image = early_memremap(bgrt_tab->image_address, sizeof(bmp_header)); + image = memremap(bgrt_tab->image_address, sizeof(bmp_header), MEMREMAP_WB); if (!image) { pr_err("Ignoring BGRT: failed to map image header memory\n"); return; }

memcpy(&bmp_header, image, sizeof(bmp_header)); - early_memunmap(image, sizeof(bmp_header)); + memunmap(image); bgrt_image_size = bmp_header.size;

bgrt_image = kmalloc(bgrt_image_size, GFP_KERNEL | __GFP_NOWARN); @@ -86,7 +86,7 @@ void __init efi_bgrt_init(void) return; }

- image = early_memremap(bgrt_tab->image_address, bmp_header.size); + image = memremap(bgrt_tab->image_address, bmp_header.size, MEMREMAP_WB); if (!image) { pr_err("Ignoring BGRT: failed to map image memory\n"); kfree(bgrt_image); @@ -95,5 +95,5 @@ void __init efi_bgrt_init(void) }

memcpy(bgrt_image, image, bgrt_image_size); - early_memunmap(image, bmp_header.size); + memunmap(image); }

Patches currently in stable-queue which might be from matt@codeblueprint.co.uk are

queue-4.4/x86-mm-pat-ensure-cpa-pfn-only-contains-page-frame-numbers.patch queue-4.4/x86-efi-hoist-page-table-switching-code-into-efi_call_virt.patch queue-4.4/x86-efi-build-our-own-page-table-structures.patch queue-4.4/x86-efi-bgrt-replace-early_memremap-with-memremap.patch queue-4.4/x86-efi-bgrt-fix-kernel-panic-when-mapping-bgrt-data.patch