Stefan Reinauer (stefan.reinauer@coreboot.org) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/283
-gerrit
commit a05c29057681e69485387f2846b44af503f82534 Author: Stefan Reinauer reinauer@google.com Date: Sat Oct 15 11:23:04 2011 -0700
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 --- src/cpu/x86/smm/smmhandler.S | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/src/cpu/x86/smm/smmhandler.S b/src/cpu/x86/smm/smmhandler.S index 450aa53..774088e 100644 --- a/src/cpu/x86/smm/smmhandler.S +++ b/src/cpu/x86/smm/smmhandler.S @@ -83,13 +83,15 @@ smm_handler_start: andl $0x7FFAFFD1, %eax /* PG,AM,WP,NE,TS,EM,MP = 0 */ orl $0x60000001, %eax /* CD, NW, PE = 1 */ movl %eax, %cr0 - wbinvd
/* Enable protected mode */ data32 ljmp $0x08, $1f
.code32 1: + /* flush the cache after disabling it */ + wbinvd + /* Use flat data segment */ movw $0x10, %ax movw %ax, %ds