Commit 1958b5fc4010 ("x86/boot: Add early boot support when running
with SEV active") is causing kexec becomes sometimes unstable, 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 lead to
wrong memory page flag.
This patch adds a get_sev_encryption_bit_64 function to avoid this
problem. 64-bit early boot code will use this function instead, it
uses native RIP addressing to read the enc_bit which have no problem
with any location.
Fixes: 1958b5fc4010 ("x86/boot: Add early boot support when running with SEV active")
Signed-off-by: Kairui Song <kasong@xxxxxxxxxx>
---
arch/x86/boot/compressed/mem_encrypt.S | 64 ++++++++++++++++++--------
1 file changed, 45 insertions(+), 19 deletions(-)
diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S
index eaa843a52907..41933550449a 100644
--- a/arch/x86/boot/compressed/mem_encrypt.S
+++ b/arch/x86/boot/compressed/mem_encrypt.S
@@ -18,27 +18,13 @@
.text
.code32
-ENTRY(get_sev_encryption_bit)
+do_get_sev_encryption_bit:
xor %eax, %eax
#ifdef CONFIG_AMD_MEM_ENCRYPT
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
@@ -69,25 +55,65 @@ 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
+#endif /* CONFIG_AMD_MEM_ENCRYPT */
+
+ ret
+
+ENTRY(get_sev_encryption_bit)
+ xor %eax, %eax
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+ 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 2f
+
+ call do_get_sev_encryption_bit
+ movl %eax, enc_bit(%edi)
+2:
+ pop %edi
#endif /* CONFIG_AMD_MEM_ENCRYPT */
ret
ENDPROC(get_sev_encryption_bit)
.code64
+ENTRY(get_sev_encryption_bit_64)
+ xor %rax, %rax
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+ movl enc_bit(%rip), %eax
+ cmpl $0, %eax
+ jge 1f
+
+ call do_get_sev_encryption_bit
+ movl %eax, enc_bit(%rip)
+1:
+#endif /* CONFIG_AMD_MEM_ENCRYPT */
+
+ ret
+ENDPROC(get_sev_encryption_bit_64)
+
ENTRY(set_sev_encryption_mask)
#ifdef CONFIG_AMD_MEM_ENCRYPT
push %rbp
@@ -95,7 +121,7 @@ ENTRY(set_sev_encryption_mask)
movq %rsp, %rbp /* Save current stack pointer */
- call get_sev_encryption_bit /* Get the encryption bit position */
+ call get_sev_encryption_bit_64 /* Get the encryption bit position */
testl %eax, %eax
jz .Lno_sev_mask
--
2.17.1
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