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Re: [Xen-devel] reading IOPL

>>> On 03.05.12 at 19:22, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:
> On Thu, May 03, 2012 at 05:07:04PM +0100, Jan Beulich wrote:
>> Both Linux and Xen offer only ways to set the IOPL. While on native Linux
>> this is not a problem since user mode code can read the IOPL by inspecting
>> EFLAGS, on Xen this would always yield zero.
>> Now X folks appear to be using save-modify-restore cycles in some newer
>> code, and this obviously breaks under Xen, as they would restore IOPL 0
> This is in the KMS drivers or in the user-land Xorg?

Userland code (as explained above).


>> even when IOPL 3 was in effect before.
>> Since the only way to read the IOPL is xc_vcpu_getcontext() (i.e.
>> XEN_DOMCTL_getvcpucontext), I wonder whether we shouldn't add
>> e.g. a "get" counterpart to PHYSDEVOP_set_iopl.
>> Or am I overlooking some other access mechanism?
>> Jan
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