Re: [Qemu-devel] [PATCH 24/58] PPC: E500: Add PV spinning code

[Richard Henderson]

On 09/27/2011 10:17 AM, Blue Swirl wrote:
> On Tue, Sep 27, 2011 at 5:01 PM, Richard Henderson <address@hidden> wrote:
>> On 09/27/2011 09:53 AM, Blue Swirl wrote:
>>>>> So how would you emulate cache lines with line locking on KVM?
>>> The cache would be a MMIO device which registers to handle all memory
>>> space. Configuring the cache controller changes how the device
>>> operates. Put this device between CPU and memory and other devices.
>>> Performance would probably be horrible, so CPU should disable the
>>> device automatically after some time.
>>>
>>
>> Seems like a better alternative would be to add an mmio device when
>> a line is actually locked.  And the device would cover *only* the
>> locked line.  I assume that following the boot process these lines
>> are unlocked, and the normal running state of the system would have
>> none of these mmio devices active.
> 
> The BIOS may also attempt to perform tests with the cache device,
> probe for cache sizes or read back I/D TLB lines via diagnostic modes.
> That wouldn't work in your approach.

Err... why not?


r~