linux-kernel - [tip:efi/core] efi/arm: Check for LPAE support before booting a LPAE kernel

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Message-ID: <tip-2ec0f0a3a4bfab90eda8b81656f62e07abf2321f@git.kernel.org>
Date:	Mon, 22 Feb 2016 04:15:43 -0800
From:	tip-bot for Ard Biesheuvel <tipbot@...or.com>@zytor.com
To:	linux-tip-commits@...r.kernel.org@...or.com
Cc:	matt@...eblueprint.co.uk, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, hpa@...or.com, jeremy.linton@....com,
	mark.rutland@....com, torvalds@...ux-foundation.org,
	peterz@...radead.org, ard.biesheuvel@...aro.org, mingo@...nel.org
Subject: [tip:efi/core] efi/arm: Check for LPAE support before booting a LPAE kernel

Commit-ID:  2ec0f0a3a4bfab90eda8b81656f62e07abf2321f
Gitweb:     http://git.kernel.org/tip/2ec0f0a3a4bfab90eda8b81656f62e07abf2321f
Author:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
AuthorDate: Wed, 17 Feb 2016 12:36:01 +0000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 22 Feb 2016 08:26:27 +0100

efi/arm: Check for LPAE support before booting a LPAE kernel

A kernel built with support for LPAE cannot boot to a state where it
can inform the user about if it has to fail due to missing LPAE support
in the hardware.

If we happen to be booting via UEFI, we can fail gracefully so check
for LPAE support in the hardware on CONFIG_ARM_LPAE builds before
entering the kernel proper.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
Reviewed-by: Jeremy Linton <jeremy.linton@....com>
Acked-by: Mark Rutland <mark.rutland@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-efi@...r.kernel.org
Link: http://lkml.kernel.org/r/1455712566-16727-9-git-send-email-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 drivers/firmware/efi/libstub/arm32-stub.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/firmware/efi/libstub/arm32-stub.c b/drivers/firmware/efi/libstub/arm32-stub.c
index 495ebd6..6f42be4 100644
--- a/drivers/firmware/efi/libstub/arm32-stub.c
+++ b/drivers/firmware/efi/libstub/arm32-stub.c
@@ -9,6 +9,23 @@
 #include <linux/efi.h>
 #include <asm/efi.h>
 
+efi_status_t check_platform_features(efi_system_table_t *sys_table_arg)
+{
+	int block;
+
+	/* non-LPAE kernels can run anywhere */
+	if (!IS_ENABLED(CONFIG_ARM_LPAE))
+		return EFI_SUCCESS;
+
+	/* LPAE kernels need compatible hardware */
+	block = cpuid_feature_extract(CPUID_EXT_MMFR0, 0);
+	if (block < 5) {
+		pr_efi_err(sys_table_arg, "This LPAE kernel is not supported by your CPU\n");
+		return EFI_UNSUPPORTED;
+	}
+	return EFI_SUCCESS;
+}
+
 efi_status_t handle_kernel_image(efi_system_table_t *sys_table,
 				 unsigned long *image_addr,
 				 unsigned long *image_size,