From: Stefan Reinauer Date: Sat, 15 Oct 2011 18:23:04 +0000 (-0700) Subject: SMM: Move wbinvd after pmode jump X-Git-Url: http://wien.tomnetworks.com/gitweb/?p=coreboot.git;a=commitdiff_plain;h=3128685a918ee9c67a50f9753874b794008c8607 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 Change-Id: Id396acf3c8a79a9f1abcc557af6e0cce099955ec Reviewed-on: http://review.coreboot.org/283 Reviewed-by: Sven Schnelle Tested-by: build bot (Jenkins) --- diff --git a/src/cpu/x86/smm/smmhandler.S b/src/cpu/x86/smm/smmhandler.S index 450aa538f..774088e1f 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