[PATCH] Don't access HID registers if running on a Hypervisor.

Jimi Xenidis jimix at watson.ibm.com
Thu Jun 22 20:58:01 EST 2006


On Jun 21, 2006, at 7:51 PM, Olof Johansson wrote:

> On Wed, Jun 21, 2006 at 07:15:55PM -0400, Jimi Xenidis wrote:
>>
>> The following patch avoids accessing Hypervisor privilege HID
>> registers when running on a Hypervisor (MSR[HV]=0).
>
> I'm curious, why is this causing problems now?
Every once in a while I run Xen on one of our simulators thats is  
sensitive to this code that does this.
First time we hit it (a while ago) we discovered that mtsdr1 was used  
(even though a no-op)

> JS20 has been running
> that code with a hypervisor since a long time back.

970s consider this a no-op (I believe an expensive one) especially  
when you consider some of the synchronization issues around the mtspr  
HIDx.
And though this is 970 specific code, Cell and future processors,  
will no longer allow writing to to these registers if !(MSR[0]=1 &&  
MSR[PR]=0)

-JX




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