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Subject[tip:efi/core] x86/efi: Don't unmap EFI boot services code/data regions for EFI_OLD_MEMMAP and EFI_MIXED_MODE
Commit-ID:  1debf0958fa27b7c469dbf22754929ec59a7c0e7
Gitweb: https://git.kernel.org/tip/1debf0958fa27b7c469dbf22754929ec59a7c0e7
Author: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
AuthorDate: Fri, 21 Dec 2018 18:22:34 -0800
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 22 Dec 2018 20:58:30 +0100

x86/efi: Don't unmap EFI boot services code/data regions for EFI_OLD_MEMMAP and EFI_MIXED_MODE

The following commit:

d5052a7130a6 ("x86/efi: Unmap EFI boot services code/data regions from efi_pgd")

forgets to take two EFI modes into consideration, namely EFI_OLD_MEMMAP and
EFI_MIXED_MODE:

- EFI_OLD_MEMMAP is a legacy way of mapping EFI regions into swapper_pg_dir
using ioremap() and init_memory_mapping(). This feature can be enabled by
passing "efi=old_map" as kernel command line argument. But,
efi_unmap_pages() unmaps EFI boot services code/data regions *only* from
efi_pgd and hence cannot be used for unmapping EFI boot services code/data
regions from swapper_pg_dir.

Introduce a temporary fix to not unmap EFI boot services code/data regions
when EFI_OLD_MEMMAP is enabled while working on a real fix.

- EFI_MIXED_MODE is another feature where a 64-bit kernel runs on a
64-bit platform crippled by a 32-bit firmware. To support EFI_MIXED_MODE,
all RAM (i.e. namely EFI regions like EFI_CONVENTIONAL_MEMORY,
EFI_LOADER_<CODE/DATA>, EFI_BOOT_SERVICES_<CODE/DATA> and
EFI_RUNTIME_CODE/DATA regions) is mapped into efi_pgd all the time to
facilitate EFI runtime calls access it's arguments in 1:1 mode.

Hence, don't unmap EFI boot services code/data regions when booted in mixed mode.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20181222022234.7573-1-sai.praneeth.prakhya@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/platform/efi/quirks.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index 09e811b9da26..17456a1d3f04 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -380,6 +380,22 @@ static void __init efi_unmap_pages(efi_memory_desc_t *md)
u64 pa = md->phys_addr;
u64 va = md->virt_addr;

+ /*
+ * To Do: Remove this check after adding functionality to unmap EFI boot
+ * services code/data regions from direct mapping area because
+ * "efi=old_map" maps EFI regions in swapper_pg_dir.
+ */
+ if (efi_enabled(EFI_OLD_MEMMAP))
+ return;
+
+ /*
+ * EFI mixed mode has all RAM mapped to access arguments while making
+ * EFI runtime calls, hence don't unmap EFI boot services code/data
+ * regions.
+ */
+ if (!efi_is_native())
+ return;
+
if (kernel_unmap_pages_in_pgd(pgd, pa, md->num_pages))
pr_err("Failed to unmap 1:1 mapping for 0x%llx\n", pa);

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