From: David Vrabel <david.vrabel@citrix.com>
To: Julien Grall <julien.grall@citrix.com>,
David Vrabel <david.vrabel@citrix.com>,
<xen-devel@lists.xenproject.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
<stefano.stabellini@eu.citrix.com>,
<linux-kernel@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>, <ian.campbell@citrix.com>
Subject: Re: [Xen-devel] [PATCH v2 02/20] xen: Introduce a function to split a Linux page into Xen page
Date: Wed, 5 Aug 2015 16:50:33 +0100 [thread overview]
Message-ID: <55C230C9.7060506@citrix.com> (raw)
In-Reply-To: <55C21DF3.2090201@citrix.com>
On 05/08/15 15:30, Julien Grall wrote:
> Hi David,
>
> On 24/07/15 11:10, David Vrabel wrote:
>> On 24/07/15 10:54, Julien Grall wrote:
>>> On 24/07/15 10:31, David Vrabel wrote:
>>>> On 09/07/15 21:42, Julien Grall wrote:
>>>>> The Xen interface is always using 4KB page. This means that a Linux page
>>>>> may be split across multiple Xen page when the page granularity is not
>>>>> the same.
>>>>>
>>>>> This helper will break down a Linux page into 4KB chunk and call the
>>>>> helper on each of them.
>>>> [...]
>>>>> --- a/include/xen/page.h
>>>>> +++ b/include/xen/page.h
>>>>> @@ -39,4 +39,24 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS];
>>>>>
>>>>> extern unsigned long xen_released_pages;
>>>>>
>>>>> +typedef int (*xen_pfn_fn_t)(struct page *page, unsigned long pfn, void *data);
>>>>> +
>>>>> +/* Break down the page in 4KB granularity and call fn foreach xen pfn */
>>>>> +static inline int xen_apply_to_page(struct page *page, xen_pfn_fn_t fn,
>>>>> + void *data)
>>>>
>>>> I think this should be outlined (unless you have measurements that
>>>> support making it inlined).
>>>
>>> I don't have any performance measurements. Although, when Linux is using
>>> 4KB page granularity, the loop in this helper will be dropped by the
>>> helper. The code would look like:
>>>
>>> unsigned long pfn = xen_page_to_pfn(page);
>>>
>>> ret = fn(page, fn, data);
>>> if (ret)
>>> return ret;
>>>
>>> The compiler could even inline the callback (fn). So it drops 2
>>> functions call.
>>
>> Ok, keep it inlined.
>>
>>>> Also perhaps make it
>>>>
>>>> int xen_for_each_gfn(struct page *page,
>>>> xen_gfn_fn_t fn, void *data);
>>>
>>> gfn standing for Guest Frame Number right?
>>
>> Yes. This suggestion is just changing the name to make it more obvious
>> what it does.
>
> Thinking more about this suggestion. The callback (fn) is getting a 4K
> PFN in parameter and not a GFN.
I would like only APIs that deal with 64 KiB PFNs and 4 KiB GFNs. I
think having a 4 KiB "PFN" is confusing.
Can you rework this xen_for_each_gfn() to pass GFNs to fn, instead?
> This is because the balloon code seems to require having a 4K PFN in
> hand in few places. For instance XENMEM_populate_physmap and
> HYPERVISOR_update_va_mapping.
Ug. For an auto-xlate guest frame-list needs GFNs, for a PV guest
XENMEM_populate_physmap does want PFNs (so it can fill in the M2P).
Perhaps in increase_reservation:
if (auto-xlate)
frame_list[i] = page_to_gfn(page);
/* Or whatever per-GFN loop you need. */
else
frame_list[i] = page_to_pfn(page);
update_va_mapping takes VAs (e.g, __va(pfn << PAGE_SHIFT) could be
page_to_virt(page).
Sorry for being so picky here, but the inconsistency of terminology and
API misuse is already confusing and I don't want to see it get worse.
David
>
> Although, I'm not sure to understand the difference between GMFN, and
> GPFN in the hypercall doc.
>
> Regards,
>
next prev parent reply other threads:[~2015-08-05 15:50 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-09 20:42 [PATCH v2 00/20] xen/arm64: Add support for 64KB page Julien Grall
2015-07-09 20:42 ` [PATCH v2 01/20] xen: Add Xen specific page definition Julien Grall
2015-07-16 14:19 ` Stefano Stabellini
2015-07-16 14:52 ` Julien Grall
2015-07-24 9:28 ` [Xen-devel] " David Vrabel
2015-07-24 9:39 ` Julien Grall
2015-07-24 9:48 ` David Vrabel
2015-07-24 9:51 ` Julien Grall
2015-07-24 10:34 ` David Vrabel
2015-07-24 10:43 ` Ian Campbell
2015-07-24 13:03 ` Julien Grall
2015-07-09 20:42 ` [PATCH v2 02/20] xen: Introduce a function to split a Linux page into Xen page Julien Grall
2015-07-16 14:23 ` Stefano Stabellini
2015-07-16 14:54 ` [Xen-devel] " Julien Grall
2015-07-24 9:31 ` David Vrabel
2015-07-24 9:54 ` Julien Grall
2015-07-24 10:10 ` David Vrabel
2015-07-24 10:20 ` Julien Grall
2015-08-05 14:30 ` Julien Grall
2015-08-05 15:50 ` David Vrabel [this message]
2015-08-05 16:06 ` Julien Grall
2015-07-09 20:42 ` [PATCH v2 03/20] xen/grant: Introduce helpers to split a page into grant Julien Grall
2015-07-16 15:01 ` Stefano Stabellini
2015-07-16 16:07 ` Julien Grall
2015-07-17 13:10 ` [Xen-devel] " Julien Grall
2015-07-09 20:42 ` [PATCH v2 04/20] xen/grant: Add helper gnttab_page_grant_foreign_access_ref Julien Grall
2015-07-16 15:05 ` Stefano Stabellini
2015-07-16 16:12 ` [Xen-devel] " Julien Grall
2015-07-24 9:35 ` David Vrabel
2015-07-09 20:42 ` [PATCH v2 05/20] block/xen-blkfront: Split blkif_queue_request in 2 Julien Grall
2015-07-21 9:54 ` Roger Pau Monné
2015-07-21 11:12 ` [Xen-devel] " Julien Grall
2015-07-09 20:42 ` [PATCH v2 06/20] block/xen-blkfront: Store a page rather a pfn in the grant structure Julien Grall
2015-07-16 15:11 ` Stefano Stabellini
2015-07-23 17:18 ` Julien Grall
2015-07-21 10:16 ` Roger Pau Monné
2015-07-21 11:19 ` [Xen-devel] " Julien Grall
2015-07-09 20:42 ` [PATCH v2 07/20] block/xen-blkfront: split get_grant in 2 Julien Grall
2015-07-21 10:30 ` Roger Pau Monné
2015-07-21 13:03 ` [Xen-devel] " Julien Grall
2015-07-09 20:42 ` [PATCH v2 08/20] net/xen-netback: xenvif_gop_frag_copy: move GSO check out of the loop Julien Grall
2015-07-09 20:42 ` [PATCH v2 09/20] xen/biomerge: Don't allow biovec to be merge when Linux is not using 4KB page Julien Grall
2015-07-10 19:12 ` Konrad Rzeszutek Wilk
2015-07-15 8:56 ` [Xen-devel] " Julien Grall
2015-07-16 15:33 ` Stefano Stabellini
2015-07-16 16:15 ` [Xen-devel] " Julien Grall
2015-07-16 18:30 ` Konrad Rzeszutek Wilk
2015-07-17 13:20 ` Stefano Stabellini
2015-07-17 14:44 ` Julien Grall
2015-07-17 14:45 ` Stefano Stabellini
2015-07-17 14:46 ` Julien Grall
2015-07-09 20:42 ` [PATCH v2 10/20] xen/xenbus: Use Xen page definition Julien Grall
2015-07-16 15:35 ` Stefano Stabellini
2015-07-24 9:49 ` David Vrabel
2015-07-09 20:42 ` [PATCH v2 11/20] tty/hvc: xen: Use xen " Julien Grall
2015-07-16 15:36 ` Stefano Stabellini
2015-07-24 9:52 ` David Vrabel
2015-07-09 20:42 ` [PATCH v2 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux Julien Grall
2015-07-17 14:03 ` Stefano Stabellini
2015-07-17 14:32 ` Julien Grall
2015-07-09 20:42 ` [PATCH v2 13/20] xen/events: fifo: Make it running on 64KB granularity Julien Grall
2015-07-16 15:43 ` Stefano Stabellini
2015-07-16 16:18 ` [Xen-devel] " Julien Grall
2015-07-17 13:06 ` Stefano Stabellini
2015-07-24 10:36 ` David Vrabel
2015-08-06 15:43 ` [Xen-devel] " Julien Grall
2015-07-09 20:42 ` [PATCH v2 14/20] xen/grant-table: " Julien Grall
2015-07-16 15:47 ` Stefano Stabellini
2015-07-16 16:23 ` [Xen-devel] " Julien Grall
2015-07-17 13:37 ` Stefano Stabellini
2015-07-09 20:42 ` [PATCH v2 15/20] block/xen-blkfront: Make it running on 64KB page granularity Julien Grall
2015-07-21 11:06 ` Roger Pau Monné
2015-07-21 13:07 ` [Xen-devel] " Julien Grall
2015-07-09 20:42 ` [PATCH v2 16/20] block/xen-blkback: " Julien Grall
2015-07-09 20:42 ` [PATCH v2 17/20] net/xen-netfront: " Julien Grall
2015-07-20 17:26 ` [Xen-devel] " Julien Grall
2015-07-09 20:42 ` [PATCH v2 18/20] net/xen-netback: " Julien Grall
2015-07-09 20:42 ` [PATCH v2 19/20] xen/privcmd: Add support for Linux " Julien Grall
2015-07-13 20:13 ` Boris Ostrovsky
2015-07-13 22:05 ` Julien Grall
2015-07-14 15:28 ` Boris Ostrovsky
2015-07-14 15:37 ` Julien Grall
2015-07-16 17:12 ` Stefano Stabellini
2015-07-16 17:16 ` Stefano Stabellini
2015-07-17 12:50 ` [Xen-devel] " Julien Grall
2015-07-09 20:42 ` [PATCH v2 20/20] arm/xen: Add support for " Julien Grall
2015-07-20 17:54 ` [Xen-devel] [PATCH v2 00/20] xen/arm64: Add support for 64KB page Julien Grall
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