[PATCH 1/2] MdePkg/BaseIoLibIntrinsic: fix SEV (=unrolled) variants of IoWriteFifoXX()

[Laszlo Ersek <lersek@redhat.com>]

In commit b6d11d7c4678 ("MdePkg: BaseIoLibIntrinsic (IoLib class)
library", 2017-04-12), the MOV instructions in the write loops were
probably copied from the read loops. However, the operand order was not
adjusted.

As a result, the IoWriteFifoXX() routines, when invoked in SEV guests, now
overwrite the source buffer with value 0x01 / 0x0001 / 0x00000001 -- the
SevNoRepIo() function returns value 1 in EAX, in SEV guests --, and write
the same value to the target IO port.

Fix this by putting the target operand (AL / AX / EAX) first, and the
source operand (BYTE / WORD / DWORD [ESI/RSI]) second.

Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Fixes: b6d11d7c467810ea7f2e2eda46ef0bdc57bf1475
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 MdePkg/Library/BaseIoLibIntrinsic/Ia32/IoFifoSev.nasm | 6 +++---
 MdePkg/Library/BaseIoLibIntrinsic/X64/IoFifoSev.nasm  | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/MdePkg/Library/BaseIoLibIntrinsic/Ia32/IoFifoSev.nasm b/MdePkg/Library/BaseIoLibIntrinsic/Ia32/IoFifoSev.nasm
index 3e80c17d04a3..4b2af807cff8 100644
--- a/MdePkg/Library/BaseIoLibIntrinsic/Ia32/IoFifoSev.nasm
+++ b/MdePkg/Library/BaseIoLibIntrinsic/Ia32/IoFifoSev.nasm
@@ -212,7 +212,7 @@ ASM_PFX(IoWriteFifo8):
     jecxz   @IoWriteFifo8_Done
 
 @IoWriteFifo8_Loop:
-    mov     byte [esi], al
+    mov     al, byte [esi]
     out     dx, al
     inc     esi
     loop    @IoWriteFifo8_Loop
@@ -250,7 +250,7 @@ ASM_PFX(IoWriteFifo16):
     jecxz   @IoWriteFifo16_Done
 
 @IoWriteFifo16_Loop:
-    mov     word [esi], ax
+    mov     ax, word [esi]
     out     dx, ax
     add     esi, 2
     loop    @IoWriteFifo16_Loop
@@ -288,7 +288,7 @@ ASM_PFX(IoWriteFifo32):
     jecxz   @IoWriteFifo32_Done
 
 @IoWriteFifo32_Loop:
-    mov     dword [esi], eax
+    mov     eax, dword [esi]
     out     dx, eax
     add     esi, 4
     loop    @IoWriteFifo32_Loop
diff --git a/MdePkg/Library/BaseIoLibIntrinsic/X64/IoFifoSev.nasm b/MdePkg/Library/BaseIoLibIntrinsic/X64/IoFifoSev.nasm
index 26e016625b72..4d86a6cd5330 100644
--- a/MdePkg/Library/BaseIoLibIntrinsic/X64/IoFifoSev.nasm
+++ b/MdePkg/Library/BaseIoLibIntrinsic/X64/IoFifoSev.nasm
@@ -205,7 +205,7 @@ ASM_PFX(IoWriteFifo8):
     jrcxz   @IoWriteFifo8_Done
 
 @IoWriteFifo8_Loop:
-    mov     byte [rsi], al
+    mov     al, byte [rsi]
     out     dx, al
     inc     rsi
     loop    @IoWriteFifo8_Loop
@@ -241,7 +241,7 @@ ASM_PFX(IoWriteFifo16):
     jrcxz   @IoWriteFifo16_Done
 
 @IoWriteFifo16_Loop:
-    mov     word [rsi], ax
+    mov     ax, word [rsi]
     out     dx, ax
     add     rsi, 2
     loop    @IoWriteFifo16_Loop
@@ -277,7 +277,7 @@ ASM_PFX(IoWriteFifo32):
     jrcxz   @IoWriteFifo32_Done
 
 @IoWriteFifo32_Loop:
-    mov     dword [rsi], eax
+    mov     eax, dword [rsi]
     out     dx, eax
     add     rsi, 4
     loop    @IoWriteFifo32_Loop
-- 
2.14.1.3.gb7cf6e02401b