linux-kernel - [PATCH 11/29] x86/efi-bgrt: Use efi_mem_reserve() to avoid copying image data

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Date:   Fri,  9 Sep 2016 16:18:33 +0100
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     Matt Fleming <matt@...eblueprint.co.uk>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>, Dave Young <dyoung@...hat.com>,
        Josh Boyer <jwboyer@...oraproject.org>,
        Josh Triplett <josh@...htriplett.org>,
        Leif Lindholm <leif.lindholm@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Môshe van der Sterre <me@...he.nl>,
        Peter Jones <pjones@...hat.com>
Subject: [PATCH 11/29] x86/efi-bgrt: Use efi_mem_reserve() to avoid copying image data

efi_mem_reserve() allows us to permanently mark EFI boot services
regions as reserved, which means we no longer need to copy the image
data out and into a separate buffer.

Leaving the data in the original boot services region has the added
benefit that BGRT images can now be passed across kexec reboot.

Reviewed-by: Josh Triplett <josh@...htriplett.org>
Tested-by: Dave Young <dyoung@...hat.com> [kexec/kdump]
Tested-by: Ard Biesheuvel <ard.biesheuvel@...aro.org> [arm]
Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Leif Lindholm <leif.lindholm@...aro.org>
Cc: Peter Jones <pjones@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Josh Boyer <jwboyer@...oraproject.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Môshe van der Sterre <me@...he.nl>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
---
 arch/x86/platform/efi/efi-bgrt.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/arch/x86/platform/efi/efi-bgrt.c b/arch/x86/platform/efi/efi-bgrt.c
index 6a2f5691b1ab..6aad870e8962 100644
--- a/arch/x86/platform/efi/efi-bgrt.c
+++ b/arch/x86/platform/efi/efi-bgrt.c
@@ -82,21 +82,12 @@ void __init efi_bgrt_init(void)
 	}
 	bgrt_image_size = bmp_header.size;
 
-	bgrt_image = kmalloc(bgrt_image_size, GFP_KERNEL | __GFP_NOWARN);
+	bgrt_image = memremap(bgrt_tab->image_address, bmp_header.size, MEMREMAP_WB);
 	if (!bgrt_image) {
-		pr_notice("Ignoring BGRT: failed to allocate memory for image (wanted %zu bytes)\n",
-		       bgrt_image_size);
-		return;
-	}
-
-	image = memremap(bgrt_tab->image_address, bmp_header.size, MEMREMAP_WB);
-	if (!image) {
 		pr_notice("Ignoring BGRT: failed to map image memory\n");
-		kfree(bgrt_image);
 		bgrt_image = NULL;
 		return;
 	}
 
-	memcpy(bgrt_image, image, bgrt_image_size);
-	memunmap(image);
+	efi_mem_reserve(bgrt_tab->image_address, bgrt_image_size);
 }
-- 
2.9.3