Commit 1958b5fc4010 ("x86/boot: Add early boot support when running
with SEV active") is causing kexec becomes sometimes unstable even if
SEV is not active. kexec reboot won't start a second kernel bypassing
BIOS boot process, instead, the system got reset.
That's because, in get_sev_encryption_bit function, we are using
32-bit RIP-relative addressing to read the value of enc_bit, but
kexec may alloc the early boot up code to a higher location, which
is beyond 32-bit addressing limit. Some garbage will be read and
get_sev_encryption_bit will return the wrong value, which leads to
wrong memory page flag.
This patch removes the use of enc_bit, as currently, enc_bit's only
purpose is to avoid duplicated encryption bit reading, but the overhead
of reading encryption bit is so tiny, so no need to cache that.
Fixes: 1958b5fc4010 ("x86/boot: Add early boot support when running with SEV active")
Suggested-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Kairui Song <kasong@xxxxxxxxxx>
---
arch/x86/boot/compressed/mem_encrypt.S | 19 -------------------
1 file changed, 19 deletions(-)
diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S
index eaa843a52907..a480356e0ed8 100644
--- a/arch/x86/boot/compressed/mem_encrypt.S
+++ b/arch/x86/boot/compressed/mem_encrypt.S
@@ -25,20 +25,6 @@ ENTRY(get_sev_encryption_bit)
push %ebx
push %ecx
push %edx
- push %edi
-
- /*
- * RIP-relative addressing is needed to access the encryption bit
- * variable. Since we are running in 32-bit mode we need this call/pop
- * sequence to get the proper relative addressing.
- */
- call 1f
-1: popl %edi
- subl $1b, %edi
-
- movl enc_bit(%edi), %eax
- cmpl $0, %eax
- jge .Lsev_exit
/* Check if running under a hypervisor */
movl $1, %eax
@@ -69,15 +55,12 @@ ENTRY(get_sev_encryption_bit)
movl %ebx, %eax
andl $0x3f, %eax /* Return the encryption bit location */
- movl %eax, enc_bit(%edi)
jmp .Lsev_exit
.Lno_sev:
xor %eax, %eax
- movl %eax, enc_bit(%edi)
.Lsev_exit:
- pop %edi
pop %edx
pop %ecx
pop %ebx
@@ -113,8 +96,6 @@ ENTRY(set_sev_encryption_mask)
ENDPROC(set_sev_encryption_mask)
.data
-enc_bit:
- .int 0xffffffff
#ifdef CONFIG_AMD_MEM_ENCRYPT
.balign 8
--
2.17.1
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