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Date: Sun, 27 Sep 2009 13:45:00 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCHv2] qemu: target library, use it in msix
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To: Avi Kivity <avi@redhat.com>
Cc: Blue Swirl <blauwirbel@gmail.com>, qemu-devel@nongnu.org

On Sun, Sep 27, 2009 at 12:40:16PM +0200, Avi Kivity wrote:
> On 09/27/2009 10:20 AM, Michael S. Tsirkin wrote:
>> On Thu, Sep 24, 2009 at 08:50:11PM +0300, Blue Swirl wrote:
>>    
>>> On Wed, Sep 23, 2009 at 11:06 PM, Michael S. Tsirkin<mst@redhat.com>  wrote:
>>>      
>>>> This creates target.c, which builds per-target, and makes it possible
>>>> for devices to become target-independent.  Use it in msix, reverting
>>>> part of 5e520a7d500ec2569d22d80f9ef4272a34cb3c80, as we no longer have
>>>> to pass target page around.
>>>>        
>>>      
>>>> +unsigned target_page_align(unsigned value)
>>>> +{
>>>> +       return TARGET_PAGE_ALIGN(value);
>>>> +}
>>>>        
>>> This must be:
>>> target_phys_addr_t target_page_align(target_phys_addr_t value)
>>>      
>> Thinking about this some more, this function just says "align a value to
>> page size". The value might not be a bus address at all, and indeed with
>> msix use, it is not. Makes sense?
>>    
>
> In any case restricting it to unsigned invites truncation.

If the value we are aligning fits in 32 bit, so does the aligned value.

>  We can have
>
>    target_phys_addr_t target_phys_page_align();
>    target_ulong_t target_virt_page_align();

Right. And also
   target_page_align32();
   target_page_align64();

We only use a 32 bit version now (passed value is a constant),
so I think I'll only implement it, and we'll add more when
they are used.

> or just
>
>   uint64_t target_page_align();
> (which is wasteful on 32/32 guests and 32 hosts).
> -- 
> Do not meddle in the internals of kernels, for they are subtle and quick to panic.