Re: [PATCH 6/6] x86/xen: open code alloc_vm_area in arch_gnttab_valloc

From: boris . ostrovsky
Date: Tue Sep 22 2020 - 11:35:03 EST

On 9/22/20 11:27 AM, Christoph Hellwig wrote:
> On Tue, Sep 22, 2020 at 11:24:20AM -0400, boris.ostrovsky@xxxxxxxxxx wrote:
>> On 9/22/20 10:58 AM, Christoph Hellwig wrote:
>>> On Mon, Sep 21, 2020 at 04:44:10PM -0400, boris.ostrovsky@xxxxxxxxxx wrote:
>>>> This will end up incrementing area->ptes pointer. So perhaps something like
>>>> pte_t **ptes = area->ptes;
>>>> if (apply_to_page_range(&init_mm, (unsigned long)area->area->addr,
>>>>                         PAGE_SIZE * nr_frames, gnttab_apply, &ptes)) {
>>>>        ...
>>> Yeah. What do you think of this version?
>> Oh yes, this is way better. This now can actually be read without trying to mentally unwind triple pointers. (You probably want to initialize idx to zero before calling apply_to_page_range(), I am not sure it's guaranteed to be zero).
> Both instances are static variables, thus in .bss and initialized.
> So unless you insist I don't think we need a manual one.

Yes, you are right. (I thought perhaps this code could be called more than once but no, it can't).