RE: [Xen-ia64-devel] [PATCH] fix access rights in VHPT whenitr.ar!=dtr.ar

[Kouya SHIMURA <kouya@xxxxxxxxxxxxxx>]

Hi Anthony,

Exactly.
But I was not confident that it is permissive to set dtr.ar=3(RWX)
instead of dtr.ar=2(RW).
If we did that, the original value would be lost.
The value is observable by xenctx command.
And PAL_VM_TR_READ is not implemented yet but it would return the
wrong value. :)

Thanks,
Kouya

Xu, Anthony writes:
 > Hi kouya,
 > 
 > Another solution is to set dtr[1].ar=3(RWX) too,
 > This will not incur any impact.
 > Because itr[1].ar=3(RWX). There are same mapping for data and instruction.
 > 
 > The upside is there is no impossible INST_ACCESS_RIGHTS.
 > 
 > - Anthony 
 > 
 > -----Original Message-----
 > From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx 
 > [mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Kouya 
 > SHIMURA
 > Sent: 2007年3月20日 16:33
 > To: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
 > Subject: [Xen-ia64-devel] [PATCH] fix access rights in VHPT 
 > whenitr.ar!=dtr.ar
 > 
 > Hi,
 > 
 > This is a workaround patch for Windows 2003 Server.
 > Windows (vcpu>=2) set itr[1].ar=3(RWX) but dtr[1].ar=2(RW).
 > It causes a impossible INST_ACCESS_RIGHTS interruption via VHPT
 > which is used for emulating TR.
 > 
 > Surprisingly, windows ordinarily accepts this interruption. 
 > But windows sometimes crashes with the message 'PANIC_STACK_SWITCH'
 > owing to this interruption.
 > 
 > Thanks,
 > Kouya
 > 
 > Signed-off-by: Kouya Shimura <kouya@xxxxxxxxxxxxxx>


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