RE: [Xen-devel] HT support on VMX broken

["Nakajima, Jun" <jun.nakajima@xxxxxxxxx>]

>From: xen-devel-admin@xxxxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
>admin@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of Leendert van Doorn
>Sent: Wednesday, January 05, 2005 11:42 AM
>To: xen-devel@xxxxxxxxxxxxxxxxxxxxx
>Cc: m+Ian.Pratt@xxxxxxxxxxxx
>Subject: [Xen-devel] HT support on VMX broken
>
>
>Hyperthreading on VMX is broken in the xeno-unstable.bk tree. The diff
>below fixes this.
The patch looks reasonable. HT makes the case worse, but that's a
generic bug. Looks like this driver was incorporated into Xen after VMX
support was added. We need to fix the mtrr driver in Linux as well.
Copying Andrew.

Thanks,
Jun

>
>It turns out that the mtrr code clears too many bits, some of them
cause
>Xen to crash. Being a bit more precise fixes the problem.
>
>       Leendert
>
>--- generic.c.orig     2005-01-03 23:44:18.000000000 -0500
>+++ generic.c  2005-01-05 14:57:16.840893000 -0500
>@@ -250,7 +250,7 @@
>       /*  Save value of CR4 and clear Page Global Enable (bit 7)  */
>       if ( cpu_has_pge ) {
>               cr4 = read_cr4();
>-              write_cr4(cr4 & (unsigned char) ~(1 << 7));
>+              write_cr4(cr4 & ~X86_CR4_PGE);
>       }
>
>       /* Flush all TLBs via a mov %cr3, %reg; mov %reg, %cr3 */
>
>
>
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