Re: [Bochs-developers] [Qemu-devel] [PATCH v5 0/5] Support for S3 ACPI state (suspend to memory) in BIOS

[Carl-Daniel Hailfinger]

On 29.11.2008 20:42, Stanislav wrote:
> Again, I mean Bochs doesn't emulate caches. So what do you mean by catchall
> emulation ?
> To allocate kind of dummy 32K block and use it when CRAM mode and delete
> immediately after ?
>   

Yes, exactly. However, the size of the dummy block depends on your cache
size. And I have seen Intel CPUs (with 2 MB cache) which used up to 1056
kB of cache during CAR mode.

> About the way you enable CRAM mode - it would be nice if we agree to use a
> protocol which real hardware needs.
>   

Yes. That is my goal. The problem is that CPU documentation is often a
bit ambiguous about how CAR mode is enabled. AFAIK the common
denominator is the CARsize <= Cachesize setting. That is really unusual
for any point in time (during OS execution) except for the short time
where CAR is enabled in the firmware/BIOS.

> I still hope to be able to execute real hardware BIOSes on Bochs for example
>   

That would be cool. The RAM controller emulation may need some tweaking,
though.

Regards,
Carl-Daniel

> Stanislav
>
> -----Original Message-----
> From: Carl-Daniel Hailfinger [mailto:address@hidden 
> Sent: Thursday, November 27, 2008 11:05 PM
> To: address@hidden
> Cc: address@hidden
> Subject: Re: [Bochs-developers] [Qemu-devel] [PATCH v5 0/5] Support for S3
> ACPI state (suspend to memory) in BIOS
>
> On 27.11.2008 21:04, Stanislav wrote:
>   
>> What is the catchall emulation ? Could you explain/point me some docs ?
>>   
>>     
>
> Sorry, it was only a brief sentence. Basically, if the total size of all
> cached areas is not bigger than CPU cache size, no cache line will be
> evicted and the cache behaves like Cache-as-RAM (CAR). That should be
> doable in Bochs, KVM and Qemu.
>
> Or were you looking for BIOS code to enable CAR? That is indeed
> processor specific, but any of the existing CAR implementations will
> work if the catchall emulation is used.
>
> Regards,
> Carl-Daniel
>
>   


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