and actually commit efi-arm64-don-t-apply-MEMBLOCK_NOMAP-to-UEFI-memory-map-mapping.patch

efi-arm64-don-t-apply-MEMBLOCK_NOMAP-to-UEFI-memory-map-mapping.patch

@@ -0,0 +1,92 @@
+From patchwork Wed Mar 30 07:46:23 2016
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 7bit
+Subject: efi/arm64: don't apply MEMBLOCK_NOMAP to UEFI memory map mapping
+From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
+X-Patchwork-Id: 8693271
+Message-Id: <1459323983-9120-1-git-send-email-ard.biesheuvel@linaro.org>
+To: linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
+	matt@codeblueprint.co.uk
+Cc: mark.rutland@arm.com, mlangsdo@redhat.com,
+	Ard Biesheuvel <ard.biesheuvel@linaro.org>, leif.lindholm@linaro.org, 
+	jeremy.linton@arm.com, msalter@redhat.com
+Date: Wed, 30 Mar 2016 09:46:23 +0200
+
+Hi Matt,
+
+Could we queue this as a fix for v4.6 with a cc:stable for v4.5, please?
+(assuming no objections from any of the cc'ees)
+
+Thanks,
+Ard.
+
+----------8<--------------
+Commit 4dffbfc48d65 ("arm64/efi: mark UEFI reserved regions as
+MEMBLOCK_NOMAP") updated the mapping logic of both the RuntimeServices
+regions as well as the kernel's copy of the UEFI memory map to set the
+MEMBLOCK_NOMAP flag, which causes these regions to be omitted from the
+kernel direct mapping, and from being covered by a struct page.
+For the RuntimeServices regions, this is an obvious win, since the contents
+of these regions have significance to the firmware executable code itself,
+and are mapped in the EFI page tables using attributes that are described in
+the UEFI memory map, and which may differ from the attributes we use for
+mapping system RAM. It also prevents the contents from being modified
+inadvertently, since the EFI page tables are only live during runtime
+service invocations.
+
+None of these concerns apply to the allocation that covers the UEFI memory
+map, since it is entirely owned by the kernel. Setting the MEMBLOCK_NOMAP on
+the region did allow us to use ioremap_cache() to map it both on arm64 and
+on ARM, since the latter does not allow ioremap_cache() to be used on
+regions that are covered by a struct page.
+
+The ioremap_cache() on ARM restriction will be lifted in the v4.7 timeframe,
+but in the mean time, it has been reported that commit 4dffbfc48d65 causes
+a regression on 64k granule kernels. This is due to the fact that, given
+the 64 KB page size, the region that we end up removing from the kernel
+direct mapping is rounded up to 64 KB, and this 64 KB page frame may be
+shared with the initrd when booting via GRUB (which does not align its
+EFI_LOADER_DATA allocations to 64 KB like the stub does). This will crash
+the kernel as soon as it tries to access the initrd.
+
+Since the issue is specific to arm64, revert back to memblock_reserve()'ing
+the UEFI memory map when running on arm64. This is a temporary fix for v4.5
+and v4.6, and will be superseded in the v4.7 timeframe when we will be able
+to move back to memblock_reserve() unconditionally.
+
+Fixes: 4dffbfc48d65 ("arm64/efi: mark UEFI reserved regions as MEMBLOCK_NOMAP")
+Reported-by: Mark Salter <msalter@redhat.com>
+Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
+
+---
+drivers/firmware/efi/arm-init.c | 18 +++++++++++++++---
+ 1 file changed, 15 insertions(+), 3 deletions(-)
+
+diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
+index aa1f743152a2..8714f8c271ba 100644
+--- a/drivers/firmware/efi/arm-init.c
++++ b/drivers/firmware/efi/arm-init.c
+@@ -203,7 +203,19 @@ void __init efi_init(void)
+ 
+ 	reserve_regions();
+ 	early_memunmap(memmap.map, params.mmap_size);
+-	memblock_mark_nomap(params.mmap & PAGE_MASK,
+-			    PAGE_ALIGN(params.mmap_size +
+-				       (params.mmap & ~PAGE_MASK)));
++
++	if (IS_ENABLED(CONFIG_ARM)) {
++		/*
++		 * ARM currently does not allow ioremap_cache() to be called on
++		 * memory regions that are covered by struct page. So remove the
++		 * UEFI memory map from the linear mapping.
++		 */
++		memblock_mark_nomap(params.mmap & PAGE_MASK,
++				    PAGE_ALIGN(params.mmap_size +
++					       (params.mmap & ~PAGE_MASK)));
++	} else {
++		memblock_reserve(params.mmap & PAGE_MASK,
++				 PAGE_ALIGN(params.mmap_size +
++					    (params.mmap & ~PAGE_MASK)));
++	}
+ }