From: Jan Beulich <jbeulich@suse.com>
To: Julien Grall <julien@xen.org>
Cc: "Kevin Tian" <kevin.tian@intel.com>, "Wei Liu" <wl@xen.org>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Julien Grall" <jgrall@amazon.com>, "Tim Deegan" <tim@xen.org>,
"George Dunlap" <george.dunlap@citrix.com>,
"Jun Nakajima" <jun.nakajima@intel.com>,
xen-devel@lists.xenproject.org,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH 05/17] xen/x86: Remove the non-typesafe version of pagetable_* helpers
Date: Mon, 20 Apr 2020 11:16:41 +0200 [thread overview]
Message-ID: <6af445d8-636f-a19e-ac53-9c66ae9f61c5@suse.com> (raw)
In-Reply-To: <f72f5c31-c437-549a-9d8b-8b836caf699b@xen.org>
On 18.04.2020 12:23, Julien Grall wrote:
> On 30/03/2020 08:52, Jan Beulich wrote:
>> On 28.03.2020 11:52, Julien Grall wrote:
>>> On 26/03/2020 15:39, Jan Beulich wrote:
>>>> On 22.03.2020 17:14, julien@xen.org wrote:
>>>>> @@ -3116,24 +3116,24 @@ int vcpu_destroy_pagetables(struct vcpu *v)
>>>>> /* Free that page if non-zero */
>>>>> do {
>>>>> - if ( mfn )
>>>>> + if ( !mfn_eq(mfn, _mfn(0)) )
>>>>
>>>> I admit I'm not fully certain either, but at the first glance
>>>>
>>>> if ( mfn_x(mfn) )
>>>>
>>>> would seem more in line with the original code to me (and then
>>>> also elsewhere).
>>>
>>> It is doing *exactly* the same things. The whole point of typesafe
>>> is to use typesafe helper not open-coding test everywhere.
>>>
>>> It is also easier to spot any use of MFN 0 within the code as you
>>> know could grep "_mfn(0)".
>>>
>>> Therefore I will insist to the code as-is.
>>
>> What I insit on is that readability of the result of such changes be
>> also kept in mind. The mfn_eq() construct is (I think) clearly less
>> easy to read and recognize than the simpler alternative suggested.
>
> If mfn_eq() is less clear, then where do you draw the line when the
> macro should or not be used?
I'm afraid there may not be a clear line to draw until everything
got converted. I do seem to recall though that, perhaps in a
different context, Andrew recently agreed with my view here (Andrew,
please correct me if I'm wrong). It being a fuzzy thing, I guess
maintainers get to judge ...
Jan
next prev parent reply other threads:[~2020-04-20 9:17 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-22 16:14 [Xen-devel] [PATCH 00/17] Bunch of typesafe conversion julien
2020-03-22 16:14 ` [Xen-devel] [PATCH 01/17] xen/x86: Introduce helpers to generate/convert the CR3 from/to a MFN/GFN julien
2020-03-25 14:46 ` Jan Beulich
2020-03-28 10:14 ` Julien Grall
2020-03-30 7:38 ` Jan Beulich
2020-04-16 11:50 ` Julien Grall
2020-03-22 16:14 ` [Xen-devel] [PATCH 02/17] xen/x86_64: Convert do_page_walk() to use typesafe MFN julien
2020-03-25 14:51 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 03/17] xen/mm: Move the MM types in a separate header julien
2020-03-25 15:00 ` Jan Beulich
2020-03-25 18:09 ` Julien Grall
2020-03-26 9:02 ` Jan Beulich
2020-03-28 10:15 ` Julien Grall
2020-03-22 16:14 ` [Xen-devel] [PATCH 04/17] xen: Convert virt_to_mfn() and mfn_to_virt() to use typesafe MFN julien
2020-03-25 15:27 ` Jan Beulich
2020-03-25 18:21 ` Julien Grall
2020-03-26 9:09 ` Jan Beulich
2020-03-28 10:33 ` Julien Grall
2020-03-22 16:14 ` [Xen-devel] [PATCH 05/17] xen/x86: Remove the non-typesafe version of pagetable_* helpers julien
2020-03-26 15:39 ` Jan Beulich
2020-03-28 10:52 ` Julien Grall
2020-03-30 7:52 ` Jan Beulich
2020-04-18 10:23 ` Julien Grall
2020-04-20 9:16 ` Jan Beulich [this message]
2020-04-20 10:10 ` Julien Grall
2020-04-20 12:14 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 06/17] xen/x86: mm: Fix the comment on top put_page_from_l2e() to use 'mfn' julien
2020-03-26 15:51 ` Jan Beulich
2020-04-18 10:54 ` Julien Grall
2020-03-22 16:14 ` [Xen-devel] [PATCH 07/17] xen/x86: traps: Convert __page_fault_type() to use typesafe MFN julien
2020-03-26 15:54 ` Jan Beulich
2020-04-18 11:01 ` Julien Grall
2020-04-18 11:43 ` Julien Grall
2020-04-20 9:19 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 08/17] xen/x86: traps: Convert show_page_walk() " julien
2020-03-22 16:14 ` [Xen-devel] [PATCH 09/17] xen/x86: Reduce the number of use of l*e_{from, get}_pfn() julien
2020-03-27 10:52 ` Jan Beulich
2020-03-28 10:53 ` Julien Grall
2020-03-22 16:14 ` [Xen-devel] [PATCH 10/17] xen/x86: pv: Use maddr_to_mfn(...) instead of the open-coding version julien
2020-03-27 11:34 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 11/17] xen/x86: nested_ept: Fix typo in the message in nept_translate_l2ga() julien
2020-03-27 11:35 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 12/17] xen/x86: p2m: Remove duplicate error message in p2m_pt_audit_p2m() julien
2020-03-27 11:35 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 13/17] xen/x86: p2m: Reflow P2M_PRINTK()s " julien
2020-03-27 11:36 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 14/17] xen/x86: mm: Re-implement set_gpfn_from_mfn() as a static inline function julien
2020-03-27 12:44 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 15/17] xen/x86: p2m: Rework printk format in audit_p2m() julien
2020-03-27 12:45 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 16/17] xen/mm: Convert {s, g}et_gpfn_from_mfn() to use typesafe MFN julien
2020-03-23 12:11 ` Hongyan Xia
2020-03-23 12:26 ` Julien Grall
2020-03-27 13:15 ` Jan Beulich
2020-03-28 11:14 ` Julien Grall
2020-03-30 8:10 ` Jan Beulich
2020-03-22 16:14 ` [Xen-devel] [PATCH 17/17] xen: Switch parameter in get_page_from_gfn to use typesafe gfn julien
2020-03-23 8:37 ` Paul Durrant
2020-03-23 10:26 ` Julien Grall
2020-03-27 13:50 ` Jan Beulich
2020-03-27 13:59 ` Julien Grall
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