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Date: Mon, 18 Jan 2010 15:58:51 +0200
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] [PATCHv2 1/3] qemu: memory notifiers
References: <cover.1262634464.git.mst@redhat.com>
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: gleb@redhat.com, qemu-devel@nongnu.org

On 01/18/2010 03:52 PM, Michael S. Tsirkin wrote:
> On Mon, Jan 18, 2010 at 03:02:59PM +0200, Avi Kivity wrote:
>    
>> On 01/04/2010 09:49 PM, Michael S. Tsirkin wrote:
>>      
>>> This adds notifiers for phys memory changes: a set of callbacks that
>>> vhost can register and update kernel accordingly.  Down the road, kvm
>>> code can be switched to use these as well, instead of calling kvm code
>>> directly from exec.c as is done now.
>>>
>>>
>>> +
>>> +static void phys_page_for_each_in_l1_map(PhysPageDesc **phys_map,
>>> +                                         CPUPhysMemoryClient *client)
>>> +{
>>> +    PhysPageDesc *pd;
>>> +    int l1, l2;
>>> +
>>> +    for (l1 = 0; l1<   L1_SIZE; ++l1) {
>>> +        pd = phys_map[l1];
>>> +        if (!pd) {
>>> +            continue;
>>> +        }
>>> +        for (l2 = 0; l2<   L2_SIZE; ++l2) {
>>> +            if (pd[l2].phys_offset == IO_MEM_UNASSIGNED) {
>>> +                continue;
>>> +            }
>>> +            client->set_memory(client, pd[l2].region_offset,
>>> +                               TARGET_PAGE_SIZE, pd[l2].phys_offset);
>>> +        }
>>> +    }
>>> +}
>>> +
>>> +static void phys_page_for_each(CPUPhysMemoryClient *client)
>>> +{
>>> +#if TARGET_PHYS_ADDR_SPACE_BITS>   32
>>> +
>>> +#if TARGET_PHYS_ADDR_SPACE_BITS>   (32 + L1_BITS)
>>> +#error unsupported TARGET_PHYS_ADDR_SPACE_BITS
>>> +#endif
>>> +    void **phys_map = (void **)l1_phys_map;
>>> +    int l1;
>>> +    if (!l1_phys_map) {
>>> +        return;
>>> +    }
>>> +    for (l1 = 0; l1<   L1_SIZE; ++l1) {
>>> +        if (phys_map[l1]) {
>>> +            phys_page_for_each_in_l1_map(phys_map[l1], client);
>>> +        }
>>> +    }
>>> +#else
>>> +    if (!l1_phys_map) {
>>> +        return;
>>> +    }
>>> +    phys_page_for_each_in_l1_map(l1_phys_map, client);
>>> +#endif
>>> +}
>>>
>>>        
>> This looks pretty frightening.  What is it needed for?
>>      
> The point is that clients can be registered at any point.
>
> A client that registered when memory is present needs to
> be notified about it.
>    

It looks very expensive.  Maybe we mandate clients be registered at 
init-time?

Long term we need to move to a range based memory description.

-- 
error compiling committee.c: too many arguments to function