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SMM: Move wbinvd after pmode jump 

According to Rudolf Marek putting a memory instruction between
the CR0 write and the jmp in protected mode switching might hang the
machine. Move it after the jmp.

There might be a better solution for this, such as enabling the cache, as
keeping it disabled does not prevent cache poisoning attacks, so there is no
real point.

However, Intel docs say that SMM code in ASEG is always running uncached, so
we might want to consider running SMM out of TSEG instead, as well.

Signed-off-by: Stefan Reinauer <reinauer@google.com>
Change-Id: Id396acf3c8a79a9f1abcc557af6e0cce099955ec
Reviewed-on: http://review.coreboot.org/283
Reviewed-by: Sven Schnelle <svens@stackframe.org>
Tested-by: build bot (Jenkins)
This commit is contained in:
Stefan Reinauer 2011-10-15 11:23:04 -07:00 committed by Stefan Reinauer
parent 1377491ac7
commit 3128685a91
1 changed files with 3 additions and 1 deletions
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4
src/cpu/x86/smm/smmhandler.S
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@ -83,13 +83,15 @@ smm_handler_start:
andl $0x7FFAFFD1, %eax /* PG,AM,WP,NE,TS,EM,MP = 0 */ andl $0x7FFAFFD1, %eax /* PG,AM,WP,NE,TS,EM,MP = 0 */
orl $0x60000001, %eax /* CD, NW, PE = 1 */ orl $0x60000001, %eax /* CD, NW, PE = 1 */
movl %eax, %cr0 movl %eax, %cr0
wbinvd
/* Enable protected mode */ /* Enable protected mode */
data32 ljmp $0x08, $1f data32 ljmp $0x08, $1f
.code32 .code32
1: 1:
/* flush the cache after disabling it */
wbinvd
/* Use flat data segment */ /* Use flat data segment */
movw $0x10, %ax movw $0x10, %ax
movw %ax, %ds movw %ax, %ds