Re: [PATCH] x86/xen: Warn when there's no mfn for pfn

[David Vrabel <david.vrabel@citrix.com>]

On 02/04/15 08:28, Ross Lagerwall wrote:
> I recently had to debug dom0 taking a fatal page fault and it would have
> been useful if it warned when creating a non-present pte if there's no
> mfn for a pfn.

This will trigger for ever PTE covering memory hotplugged by the balloon
driver, so I don't think we can take this.

David

> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -397,6 +397,7 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
>  		 * pte_mfn_to_pfn is asymmetric.
>  		 */
>  		if (unlikely(mfn == INVALID_P2M_ENTRY)) {
> +			printk(KERN_WARNING "No mfn for pfn %lx, creating non-present pte\n", pfn);
>  			mfn = 0;
>  			flags = 0;
>  		} else
>