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

Sai Praneeth Prakhya · Ingo Molnar · commit 1debf0958fa2 · 2018-12-22T20:58:30.000+01:00
The following commit: d5052a7 ("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>
diff --git 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);
 
