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Re: [Xen-devel] [Q] Allow rdpmc access from DOM-0

To: "Mohapatra, Hemant" <Hemant.Mohapatra@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [Q] Allow rdpmc access from DOM-0
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 06 Sep 2007 16:30:04 +0100
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On 6/9/07 16:23, "Mohapatra, Hemant" <Hemant.Mohapatra@xxxxxxx> wrote:

> My bad; I should've mentioned this before: I already have allowed access
> to the appropriate MSRs and can read/write to them using rdmsr/wrmsr on
> DOM-0. It was easy to add them to the white-list since the opcode was
> already being trapped and virtualized and it was only a matter of adding
> access to the MSRs I needed specifically.
> I have worked with Xenoprof but I am essentially trying to port a few
> applications to Xen here and trying to re-write them in conjunction with
> Xenoprof seems like the round-about way of doing it. I am trying to
> follow the route of how rdmsr/wrmsr were virtualized so that I can do
> the same with rdpmc. I see no harm in this since RDMSR is already
> allowed from Dom0.

Your problem might then be that your RDPMC emulation path is only executed
if the instruction was trapped in guest kernel mode. I guess you are trying
to execute it in guest user mode, and you may find that this mode is tested
for before you reach the RDPMC case that you've added.

 -- Keir

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