From: Tom Lendacky <thomas.lendacky@amd.com>
Date: Fri, 28 Jul 2017 11:01:16 -0500
Subject: x86/mm, kexec: Fix memory corruption with SME on successive kexecs
Git-commit: 4e237903f95db585b976e7311de2bfdaaf0f6e31
Patch-mainline: v4.14-rc1
References: fate#322123
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: Tom 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: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov <bp@suse.de>
---
arch/x86/include/asm/kexec.h | 3 ++-
arch/x86/kernel/machine_kexec_64.c | 3 ++-
arch/x86/kernel/relocate_kernel_64.S | 14 ++++++++++++++
3 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index e8183acf931f..942c1f444da8 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -147,7 +147,8 @@ static inline void crash_setup_regs(struct pt_regs *newregs,
relocate_kernel(unsigned long indirection_page,
unsigned long page_list,
unsigned long start_address,
- unsigned int preserve_context);
+ unsigned int preserve_context,
+ unsigned int sme_active);
#endif
#define ARCH_HAS_KIMAGE_ARCH
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 9cf8daacc046..1f790cf9d38f 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -335,7 +335,8 @@ void machine_kexec(struct kimage *image)
image->start = relocate_kernel((unsigned long)image->head,
(unsigned long)page_list,
image->start,
- image->preserve_context);
+ image->preserve_context,
+ sme_active());
#ifdef CONFIG_KEXEC_JUMP
if (image->preserve_context)
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 98111b38ebfd..307d3bac5f04 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -47,6 +47,7 @@ relocate_kernel:
* %rsi page_list
* %rdx start address
* %rcx preserve_context
+ * %r8 sme_active
*/
/* Save the CPU context, used for jumping back */
@@ -71,6 +72,9 @@ relocate_kernel:
pushq $0
popfq
+ /* Save SME active flag */
+ movq %r8, %r12
+
/*
* get physical address of control page now
* this is impossible after page table switch
@@ -132,6 +136,16 @@ identity_mapped:
/* Flush the TLB (needed?) */
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
call swap_pages