CentOS 7 gets into trouble when compiling Xen citing:
flushtlb.c: Assembler messages:
flushtlb.c:149: Error: value of 256 too large for field of 1 bytes at 1
The line number is wrong, and the error message not helpful. It turns out
that the intermediate generated assembly was
# 139 "arch/x86/flushtlb.c" 1
661:
rex clflush (%r15)
662:
.pushsection .altinstructions,"a"
and it was having trouble combining the explicit REX prefix with the REX.B
required for the use of %r15.
Follow what Linux does and use a redundant %ds prefix instead, for a final
generated instruction of `3e 41 0f ae 3f`
While modifying this line, fix the indentation which was out by one space.
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
---
xen/arch/x86/flushtlb.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/xen/arch/x86/flushtlb.c b/xen/arch/x86/flushtlb.c
index 90a004f..727434e 100644
--- a/xen/arch/x86/flushtlb.c
+++ b/xen/arch/x86/flushtlb.c
@@ -141,10 +141,10 @@ void flush_area_local(const void *va, unsigned int flags)
{
alternative(ASM_NOP3, "sfence", X86_FEATURE_CLFLUSHOPT);
for ( i = 0; i < sz; i += c->x86_clflush_size )
- alternative_input("rex clflush %0",
- "data16 clflush %0",
- X86_FEATURE_CLFLUSHOPT,
- "m" (((const char *)va)[i]));
+ alternative_input(".byte 0x3e; clflush %0", /* %ds override. */
+ "data16 clflush %0", /* clflushopt. */
+ X86_FEATURE_CLFLUSHOPT,
+ "m" (((const char *)va)[i]));
}
else
{
--
2.1.4
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