Xen devel - Jul 2007 - [PATCH] vmwrite high 32 bits of 64bit VMCS fields when in PAE mode

vmwrite higher 32 bits of 64bit VMCS fields when in PAE mode.
Signed-off-by: Xin Li <xin.b.li@intel.com>


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

Is this necessary? Writes to low halves clear top halves, and these data
structures will always be below 4GB, right?

Are you just being super safe? :-)

 -- Keir

On 10/7/07 16:52, "Li, Xin B" <xin.b.li@intel.com> wrote:
> vmwrite higher 32 bits of 64bit VMCS fields when in PAE mode.
> Signed-off-by: Xin Li <xin.b.li@intel.com>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

On 10/7/07 18:57, "Keir Fraser" <keir@xensource.com> wrote:
> Is this necessary? Writes to low halves clear top halves, and these data
> structures will always be below 4GB, right?
> 
> Are you just being super safe? :-)
Oh, furthermore with a 32-bit build of Xen we have to be safe for the case
that VMX_BASIC_MSR[48]==1 (which Vol 3B Appendix G.1 says is true for non
Intel64 CPUs like Yonah). In this case the physical pointers poked into the
VMCS are limited to 32 bits. We may as well limit all such structures to
below 4GB in all cases with a 32-bit build of Xen.

 -- Keir


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

>-----Original Message-----
>From: Keir Fraser [mailto:keir@xensource.com] 
>Sent: Wednesday, July 11, 2007 1:57 AM
>To: Li, Xin B; xen-devel@lists.xensource.com
>Subject: Re: [Xen-devel] [PATCH] vmwrite high 32 bits of 64bit 
>VMCS fields when in PAE mode
>
>Is this necessary? Writes to low halves clear top halves, and 
>these data structures will always be below 4GB, right?
On PAE, I think it may be above 4G.
-Xin 

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

>> Is this necessary? Writes to low halves clear top halves, and these
data
>> structures will always be below 4GB, right?
>> 
>> Are you just being super safe? :-)
>
>Oh, furthermore with a 32-bit build of Xen we have to be safe for the
case
>that VMX_BASIC_MSR[48]==1 (which Vol 3B Appendix G.1 says is true for
non
>Intel64 CPUs like Yonah). In this case the physical pointers poked into
the
>VMCS are limited to 32 bits. We may as well limit all such structures
to
>below 4GB in all cases with a 32-bit build of Xen.
>
So we need keep this mind for all data structures referenced by pointers
in a VMCS when on 32bit Xen, or maybe how about add a memory allocation
function wrapper for this purpose?
-Xin

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

On 11/7/07 06:58, "Li, Xin B" <xin.b.li@intel.com> wrote:
>> Oh, furthermore with a 32-bit build of Xen we have to be safe for the
> case
>> that VMX_BASIC_MSR[48]==1 (which Vol 3B Appendix G.1 says is true for
> non
>> Intel64 CPUs like Yonah). In this case the physical pointers poked into
> the
>> VMCS are limited to 32 bits. We may as well limit all such structures
> to
>> below 4GB in all cases with a 32-bit build of Xen.
>> 
> 
> So we need keep this mind for all data structures referenced by pointers
> in a VMCS when on 32bit Xen, or maybe how about add a memory allocation
> function wrapper for this purpose?
I think I fixed this now. Most of the structures were inside the Xen image
(io_bitmap) or were allocated from Xen heap (msr_bitmap, vmcs, apic_access).
The only exception was the apic_regs page -- I now restricted it to 32-bit
addresses on a 32-bit build of Xen if running on an Intel CPU.

Changeset 15526 in the staging tree.

 -- Keir


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel