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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: linux-efi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H . Peter Anvin" <hpa@zytor.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	linux-kernel@vger.kernel.org,
	Matt Fleming <matt@codeblueprint.co.uk>
Subject: [PATCH 07/14] drivers/fbdev: efifb: allow BAR to be moved instead of claiming it
Date: Fri, 18 Aug 2017 20:49:40 +0100
Message-ID: <20170818194947.19347-8-ard.biesheuvel@linaro.org> (raw)
In-Reply-To: <20170818194947.19347-1-ard.biesheuvel@linaro.org>

On UEFI systems, the firmware may expose a Graphics Output Protocol (GOP)
instance to which the efifb driver attempts to attach in order to provide
a minimal, unaccelerated framebuffer. The GOP protocol itself is not very
sophisticated, and only describes the offset and size of the framebuffer
in memory, and the pixel format.

If the GOP framebuffer is provided by a PCI device, it will have been
configured and enabled by the UEFI firmware, and the GOP protocol will
simply point into a live BAR region. However, the GOP protocol itself does
not describe this relation, and so we have to take care not to reconfigure
the BAR without taking efifb's dependency on it into account.

Commit 55d728a40d36 ("efi/fb: Avoid reconfiguration of BAR that covers
the framebuffer") attempted to do so by claiming the BAR resource early
on, which prevents the PCI resource allocation routines from changing it.
However, it turns out that this only works if the PCI device is not
behind any bridges, since the bridge resources need to be claimed first.

So instead, allow the BAR to be moved, but make the efifb driver deal
with that gracefully. So record the resource that covers the BAR early
on, and if it turns out to have moved by the time we probe the efifb
driver, update the framebuffer address accordingly.

While this is less likely to occur on x86, given that the firmware's
PCI resource allocation is more likely to be preserved, this is a
worthwhile sanity check to have in place, and so let's remove the
preprocessor conditional that makes it !X86 only.

Cc: Matt Fleming <matt@codeblueprint.co.uk>
Reviewed-by: Peter Jones <pjones@redhat.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/video/fbdev/efifb.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
index ff01bed7112f..994b5f3a4d73 100644
--- a/drivers/video/fbdev/efifb.c
+++ b/drivers/video/fbdev/efifb.c
@@ -146,6 +146,10 @@ ATTRIBUTE_GROUPS(efifb);
 
 static bool pci_dev_disabled;	/* FB base matches BAR of a disabled device */
 
+static struct pci_dev *efifb_pci_dev;	/* dev with BAR covering the efifb */
+static struct resource *bar_resource;
+static u64 bar_offset;
+
 static int efifb_probe(struct platform_device *dev)
 {
 	struct fb_info *info;
@@ -200,6 +204,13 @@ static int efifb_probe(struct platform_device *dev)
 		efifb_fix.smem_start |= ext_lfb_base;
 	}
 
+	if (bar_resource &&
+	    bar_resource->start + bar_offset != efifb_fix.smem_start) {
+		dev_info(&efifb_pci_dev->dev,
+			 "BAR has moved, updating efifb address\n");
+		efifb_fix.smem_start = bar_resource->start + bar_offset;
+	}
+
 	efifb_defined.bits_per_pixel = screen_info.lfb_depth;
 	efifb_defined.xres = screen_info.lfb_width;
 	efifb_defined.yres = screen_info.lfb_height;
@@ -364,15 +375,13 @@ static struct platform_driver efifb_driver = {
 
 builtin_platform_driver(efifb_driver);
 
-#if defined(CONFIG_PCI) && !defined(CONFIG_X86)
-
-static bool pci_bar_found;	/* did we find a BAR matching the efifb base? */
+#if defined(CONFIG_PCI)
 
-static void claim_efifb_bar(struct pci_dev *dev, int idx)
+static void record_efifb_bar_resource(struct pci_dev *dev, int idx, u64 offset)
 {
 	u16 word;
 
-	pci_bar_found = true;
+	efifb_pci_dev = dev;
 
 	pci_read_config_word(dev, PCI_COMMAND, &word);
 	if (!(word & PCI_COMMAND_MEMORY)) {
@@ -383,12 +392,8 @@ static void claim_efifb_bar(struct pci_dev *dev, int idx)
 		return;
 	}
 
-	if (pci_claim_resource(dev, idx)) {
-		pci_dev_disabled = true;
-		dev_err(&dev->dev,
-			"BAR %d: failed to claim resource for efifb!\n", idx);
-		return;
-	}
+	bar_resource = &dev->resource[idx];
+	bar_offset = offset;
 
 	dev_info(&dev->dev, "BAR %d: assigned to efifb\n", idx);
 }
@@ -399,7 +404,7 @@ static void efifb_fixup_resources(struct pci_dev *dev)
 	u64 size = screen_info.lfb_size;
 	int i;
 
-	if (pci_bar_found || screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
+	if (efifb_pci_dev || screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
 		return;
 
 	if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
@@ -415,7 +420,7 @@ static void efifb_fixup_resources(struct pci_dev *dev)
 			continue;
 
 		if (res->start <= base && res->end >= base + size - 1) {
-			claim_efifb_bar(dev, i);
+			record_efifb_bar_resource(dev, i, base - res->start);
 			break;
 		}
 	}
-- 
2.11.0

  parent reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-18 19:49 [GIT PULL 00/14] EFI changes for v4.14 Ard Biesheuvel
2017-08-18 19:49 ` [PATCH 01/14] efi: arm: Don't mark ACPI reclaim memory as MEMBLOCK_NOMAP Ard Biesheuvel
2017-08-18 19:49 ` [PATCH 02/14] efi/libstub: arm64: use hidden attribute for struct screen_info reference Ard Biesheuvel
2017-08-18 19:49 ` [PATCH 04/14] efi/libstub: arm64: set -fpie when building the EFI stub Ard Biesheuvel
2017-08-18 19:49 ` [PATCH 05/14] efi: arm/arm64: Add missing assignment of efi.config_table Ard Biesheuvel
2017-08-18 19:49 ` Ard Biesheuvel [this message]
2017-08-18 19:49 ` [PATCH 10/14] arm: efi: replace open coded constants with symbolic ones Ard Biesheuvel
2017-08-18 19:49 ` [PATCH 12/14] firmware: dcdbas: constify attribute_group structures Ard Biesheuvel
     [not found] ` <20170818194947.19347-1-ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2017-08-18 19:49   ` [PATCH 03/14] efi/libstub: arm64: force 'hidden' visibility for section markers Ard Biesheuvel
2017-08-18 19:49   ` [PATCH 06/14] efi/reboot: Fall back to original power-off method if EFI_RESET_SHUTDOWN returns Ard Biesheuvel
2017-08-18 19:49   ` [PATCH 08/14] arm: efi: remove forbidden values from the PE/COFF header Ard Biesheuvel
2017-08-18 19:49   ` [PATCH 09/14] arm: efi: remove pointless dummy .reloc section Ard Biesheuvel
2017-08-18 19:49   ` [PATCH 11/14] arm: efi: split zImage code and data into separate PE/COFF sections Ard Biesheuvel
2017-08-18 19:49   ` [PATCH 13/14] firmware: efi: constify attribute_group structures Ard Biesheuvel
2017-08-18 19:49 ` [PATCH 14/14] firmware: efi: esrt: " Ard Biesheuvel
2017-08-21  9:34 ` [GIT PULL 00/14] EFI changes for v4.14 Ingo Molnar

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