[RFC Part1 PATCH v3 13/17] x86/io: Unroll string I/O when SEV is active

Brijesh Singh
2017-07-24T19:07:53Z

From: Tom Lendacky <thomas.lendacky@amd.com>

Secure Encrypted Virtualization (SEV) does not support string I/O, so
unroll the string I/O operation into a loop operating on one element at
a time.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/include/asm/io.h | 26 ++++++++++++++++++++++----
1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index e080a39..2f3c002 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -327,14 +327,32 @@ static inline unsigned type in##bwl##_p(int port) \
\
static inline void outs##bwl(int port, const void *addr, unsigned long count) \
{ \
- asm volatile("rep; outs" #bwl \
- : "+S"(addr), "+c"(count) : "d"(port)); \
+ if (sev_active()) { \
+ unsigned type *value = (unsigned type *)addr; \
+ while (count) { \
+ out##bwl(*value, port); \
+ value++; \
+ count--; \
+ } \
+ } else { \
+ asm volatile("rep; outs" #bwl \
+ : "+S"(addr), "+c"(count) : "d"(port)); \
+ } \
} \
\
static inline void ins##bwl(int port, void *addr, unsigned long count) \
{ \
- asm volatile("rep; ins" #bwl \
- : "+D"(addr), "+c"(count) : "d"(port)); \
+ if (sev_active()) { \
+ unsigned type *value = (unsigned type *)addr; \
+ while (count) { \
+ *value = in##bwl(port); \
+ value++; \
+ count--; \
+ } \
+ } else { \
+ asm volatile("rep; ins" #bwl \
+ : "+D"(addr), "+c"(count) : "d"(port)); \
+ } \
}

BUILDIO(b, b, char)
--
2.9.4