Re: [Qemu-devel] [RFC] Next gen kvm api

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 07.02.2012, at 16:23, Anthony Liguori wrote:

> On 02/07/2012 07:40 AM, Alexander Graf wrote:
>> 
>> Why? For the HPET timer register for example, we could have a simple MMIO hook that says
>> 
>>   on_read:
>>     return read_current_time() - shared_page.offset;
>>   on_write:
>>     handle_in_user_space();
>> 
>> For IDE, it would be as simple as
>> 
>>   register_pio_hook_ptr_r(PIO_IDE, SIZE_BYTE,&s->cmd[0]);
>>   for (i = 1; i<  7; i++) {
>>     register_pio_hook_ptr_r(PIO_IDE + i, SIZE_BYTE,&s->cmd[i]);
>>     register_pio_hook_ptr_w(PIO_IDE + i, SIZE_BYTE,&s->cmd[i]);
>>   }
> 
> You can't easily serialize updates to that address with the kernel since two threads are likely going to be accessing it at the same time.  That either means an expensive sync operation or a reliance on atomic instructions.

Yes. Essentially we want a mutex for them.

> But not all architectures offer non-word sized atomic instructions so it gets fairly nasty in practice.

Well, we can always require fields to be word sized.


Alex

--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux