Re: [Xen-devel] [PATCH 4/6] mm: New XENMEM, XENMEM_add_to_physmap_gmfn_range

[Tim Deegan <tim@xxxxxxx>]

At 13:32 +0000 on 08 Nov (1320759148), Tim Deegan wrote:
> At 02:20 -0700 on 08 Nov (1320718835), Jan Beulich wrote:
> > >>> On 07.11.11 at 19:25, Jean Guyader <jean.guyader@xxxxxxxxxxxxx> wrote:
> > 
> > Sorry, noticed this only now, but neither title nor description of this
> > are in sync with the actual patch.
> 
> 
> Indeed; they should be updated.  But otherwise:
> Acked-by: Tim Deegan <tim@xxxxxxx>

No, wait, that was the other patch, which I already acked!
ENOCOFFEE. :(

I have a few other comments on this patch...

> diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
> index f75011e..cca64b8 100644
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -4714,9 +4714,29 @@ long arch_memory_op(int op, XEN_GUEST_HANDLE(void) arg)
>              return -EPERM;
>          }
>  
> -        xenmem_add_to_physmap(d, xatp);
> +        if ( xatp.space != XENMAPSPACE_gmfn_range )
> +            xatp.size = 1;
> +
> +        for ( ; xatp.size > 0; xatp.size-- )
> +        {
> +            if ( hypercall_preempt_check() )
> +            {
> +                rc = -EAGAIN;
> +                break;
> +            }
> +            xenmem_add_to_physmap(d, xatp);
> +            xatp.idx++;
> +            xatp.gpfn++;
> +        }

Having moved XATP into its own function, this loop probably belongs in
that function. 

While I'm looking at it, updating two loop vars explicitly and one in
the header is a bit ugly - why not just use a while() and update all
three together?


>          rcu_unlock_domain(d);
> +        if ( rc == -EAGAIN )
> +        {
> +            if ( copy_to_guest(arg, &xatp, 1) )
> +                return -EFAULT;
> +            rc = hypercall_create_continuation(
> +                    __HYPERVISOR_memory_op, "ih", op, arg);
> +        }

I think this might need some compat glue in
arch/x86/x86_64/compat/mm.c for it to work with 32-bit callers.


Tim.

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