Re: [Xen-ia64-devel] [Patch] Fix for re-enabling PV-on-HVM on IPF

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Thu, Mar 08, 2007 at 01:06:04PM +0900, DOI Tsunehisa wrote:
> diff -r 61eb6589e720 -r b602dd142385 xen/arch/ia64/xen/mm.c
> --- a/xen/arch/ia64/xen/mm.c  Tue Mar 06 21:11:37 2007 +0900
> +++ b/xen/arch/ia64/xen/mm.c  Thu Mar 08 11:57:46 2007 +0900
> @@ -2110,12 +2125,31 @@ arch_memory_op(int op, XEN_GUEST_HANDLE(
>  
>          /* Unmap from old location, if any. */
>          gpfn = get_gpfn_from_mfn(mfn);
> -        if (gpfn != INVALID_M2P_ENTRY)
> +        if (gpfn != INVALID_M2P_ENTRY) {
> +            unsigned long x, nx;
> +            /*
> +             * guest_physmap_remove_page() (for IPF) descrements page
> +             * counter and unset PGC_allocated flag,
> +             * so pre-increment page counter and post-set flag inserted
> +             */
> +            /* pre-increment page counter */
> +            get_page(mfn_to_page(mfn), d);

Please check the return value.


> +
>              guest_physmap_remove_page(d, gpfn, mfn);
> +
> +            /* post-set PGC_allocated flag */
> +            do {
> +                x = mfn_to_page(mfn)->count_info;
> +                if ((x & PGC_count_mask) == 0)
> +                    goto out;
> +                nx = x | PGC_allocated;
> +            } while (cmpxchg_acq(&mfn_to_page(mfn)->count_info, x, nx) != x);
> +        }

checking == 0 is non-sense because we incremented it.
Probably you want to 
   if (!test_and_set_bit(page->count_info, _PGC_allocated)) {
        put_page(page);
        goto out;
   }

-- 
yamahata

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