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Commit 4e237903 authored by Tom Lendacky's avatar Tom Lendacky Committed by Ingo Molnar
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x86/mm, kexec: Fix memory corruption with SME on successive kexecs 



After issuing successive kexecs it was found that the SHA hash failed
verification when booting the kexec'd kernel.  When SME is enabled, the
change from using pages that were marked encrypted to now being marked as
not encrypted (through new identify mapped page tables) results in memory
corruption if there are any cache entries for the previously encrypted
pages. This is because separate cache entries can exist for the same
physical location but tagged both with and without the encryption bit.

To prevent this, issue a wbinvd if SME is active before copying the pages
from the source location to the destination location to clear any possible
cache entry conflicts.

Signed-off-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Cc: <kexec@lists.infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/e7fb8610af3a93e8f8ae6f214cd9249adc0df2b4.1501186516.git.thomas.lendacky@amd.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f90e2d9a

arch/x86/include/asm/kexec.h

+2 −1
Original line number Original line Diff line number Diff line
@@ -147,7 +147,8 @@ unsigned long 
relocate_kernel(unsigned long indirection_page,

relocate_kernel(unsigned long indirection_page,

		unsigned long page_list,

		unsigned long page_list,

		unsigned long start_address,

		unsigned long start_address,

		unsigned int preserve_context);

		unsigned int preserve_context,

		unsigned int sme_active);

#endif

#endif





#define ARCH_HAS_KIMAGE_ARCH

#define ARCH_HAS_KIMAGE_ARCH

arch/x86/kernel/machine_kexec_64.c

+2 −1
Original line number Original line Diff line number Diff line
@@ -335,7 +335,8 @@ void machine_kexec(struct kimage *image) 
	image->start = relocate_kernel((unsigned long)image->head,

	image->start = relocate_kernel((unsigned long)image->head,

				       (unsigned long)page_list,

				       (unsigned long)page_list,

				       image->start,

				       image->start,

				       image->preserve_context);

				       image->preserve_context,

				       sme_active());





#ifdef CONFIG_KEXEC_JUMP

#ifdef CONFIG_KEXEC_JUMP

	if (image->preserve_context)

	if (image->preserve_context)

arch/x86/kernel/relocate_kernel_64.S

+14 −0
Original line number Original line Diff line number Diff line
@@ -47,6 +47,7 @@ relocate_kernel: 
	 * %rsi page_list

	 * %rsi page_list

	 * %rdx start address

	 * %rdx start address

	 * %rcx preserve_context

	 * %rcx preserve_context

	 * %r8  sme_active

	 */

	 */





	/* Save the CPU context, used for jumping back */

	/* Save the CPU context, used for jumping back */
@@ -71,6 +72,9 @@ relocate_kernel: 
	pushq $0

	pushq $0

	popfq

	popfq





	/* Save SME active flag */

	movq	%r8, %r12



	/*

	/*

	 * get physical address of control page now

	 * get physical address of control page now

	 * this is impossible after page table switch

	 * this is impossible after page table switch
@@ -132,6 +136,16 @@ identity_mapped: 
	/* Flush the TLB (needed?) */

	/* Flush the TLB (needed?) */

	movq	%r9, %cr3

	movq	%r9, %cr3





	/*

	 * If SME is active, there could be old encrypted cache line

	 * entries that will conflict with the now unencrypted memory

	 * used by kexec. Flush the caches before copying the kernel.

	 */

	testq	%r12, %r12

	jz 1f

	wbinvd

1:



	movq	%rcx, %r11

	movq	%rcx, %r11

	call	swap_pages

	call	swap_pages