[RFC PATCH v1 15/28] x86: Unroll string I/O when SEV is active
From: Brijesh Singh <hidden>
Date: 2016-08-23 00:01:08
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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> --- 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 de25aad..130b3e2 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h@@ -303,14 +303,32 @@ 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)