Re: [Xen-ia64-devel] [PATCH] [RFC] [TAKE2] P2M/VP (incomplete) patches

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Wed, Mar 15, 2006 at 05:12:33PM +0800, Tian, Kevin wrote:

> >9191:2ac9130fb9f6_fix_grant_entry_t_frame.patch
> 
> This one is a fix and can be sent out to xen mailing list earlier. But it may 
> not be so urgent to see the issue for IA64 and x86-64. See how large 
> even 32bit can support: 4G * 4K = 16T. I don't think people ever tested on 
> it now. :-)

I agree. 32 bits might be sufficient for at least several years.


> >9192:80353e9e2e0f_grant_table_xen_part.patch
> >9193:6922c2fe7446_grant_table_linux_part.patch
> 
> Sorry that I didn't look into carefully, but why following logic:
> +#ifndef __ia64__
>       shared[ref].frame = frame;
> +#else
> +     shared[ref].frame = mfn_to_pfn(frame);//XXX
> +#endif
> 
> The caller already does virt_to_mfn which results a hypercall by your 
> model, and now another hypercall caused by mfn_to_pfn again. It's better 
> to make a decision whether frames passed from xenlinux is 
> pseudophysical or machine, and then just support it uniformly. You see 
> current grant table code can handle either case, differentiated by shadow 
> translated mode for x86. Though we have no shadow code for xen/ia64, 
> but that's the flag you can use to simplify changes.

I haven't cleaned up grant table api yet. 
I'm sure some clean up is necessary. This is the reason why XXX is there.
I'll work on it after getting vnif to work. 


> BTW, what's the intent of alloc_vm_area? Seems no one calls it. Also a 
> typo there:
> struct vm_struct* area;
> ...
> area = kmalloc(sizeof(area), GFP_KERNEL); which only gives you 8
> bytes. :-)

Oops thanks.
alloc_vm_area() is called by blkback, blktap, netback, tpmback, xenbus
to allocate virtual address area of xen I/O ring.
Allocating virtual address area which doesn't have corresponding
pseudo physical page is xen/x86-ism.
Some clean up is also needed.

-- 
yamahata

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