Re: [Xen-devel] Why CR0.WP is always set in HVM domain

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

That might work. There are other cases where pages need to be read-only for
the guest of course (e.g., live migration dirty-page logging). It might be
better just to emulate CR0.WP than fix up all the places where
must-be-read-only pages would unfortunately become writable.

 -- Keir

On 8/11/07 17:25, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

> Not sure if we can use shadow_mode_trap_reads(), i.e. when WP is clear,
> we set all user space mapping to guest page table to be non-present. And
> then do emulate in shadow for such situation. But seems
> shadow_mode_traps_reads not implemented yet :(
> 
> -- Yunhong 
> 
> 
> xen-devel-bounces@xxxxxxxxxxxxxxxxxxx <> wrote:
>> Thanks for your explaination.
>> I notice some anti-virus application clear CR0.WP, so maybe we need to
>> consider this support.
>> 
>> -- Yunhong
>> 
>> xen-devel-bounces@xxxxxxxxxxxxxxxxxxx <> wrote:
>>> It's necessary because we need to trap guest writes to pagetables,
>>> regardless of setting of guest CR0.WP. If it turns out we need
>>> to properly
>>> emulate CR0.WP then we'll need to come up with a scheme that does not
>>> require us to run the guest with real CR0.WP set. Possibly it
>>> will require
>>> us to emulate certain memory accesses.
>>> 
>>> -- Keir
>>> 
>>> On 8/11/07 14:23, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:
>>> 
>>>> In "arch/x86/hvm/vmx/vmx.c", vmx_update_guest_cr(), the CR0.WP is
> always
>>>>         set as following code: v->arch.hvm_vcpu.hw_cr[0] =
>>>>             v->arch.hvm_vcpu.guest_cr[0] |
>>>>             X86_CR0_PE | X86_CR0_NE | X86_CR0_PG | X86_CR0_WP;
>>>> 
>>>> I'm wondering are there any special reason for this? I try to check
>>>> shadow code and didn't find any clue.
>>>> Can anyone give me some hints?
>>>> 
>>>> Thanks
>>>> Yunhong Jiang
>>>> 
>>>> _______________________________________________
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>>>> http://lists.xensource.com/xen-devel
>>> 
>>> 
>>> 
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>> 
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