From: Luca Fancellu <luca.fancellu@arm.com>
To: Julien Grall <julien@xen.org>
Cc: xen-devel@lists.xenproject.org,
Bertrand Marquis <bertrand.marquis@arm.com>,
wei.chen@arm.com, Stefano Stabellini <sstabellini@kernel.org>,
Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
Rahul Singh <rahul.singh@arm.com>
Subject: Re: [PATCH v4 2/4] xen/arm: Handle cases when hardware_domain is NULL
Date: Wed, 14 Apr 2021 14:47:45 +0100 [thread overview]
Message-ID: <F5760FAD-466F-46EC-A3A4-BAC2B5E73BC8@arm.com> (raw)
In-Reply-To: <269e20a7-9f2c-f989-0ea0-7ab6c6bb9c11@xen.org>
> On 14 Apr 2021, at 14:45, Julien Grall <julien@xen.org> wrote:
>
> Hi Luca,
>
> On 14/04/2021 12:29, Luca Fancellu wrote:
>>> On 14 Apr 2021, at 12:16, Julien Grall <julien@xen.org> wrote:
>>>
>>> Hi Luca,
>>>
>>> On 14/04/2021 10:14, Luca Fancellu wrote:
>>>> Among the common and arm codebase there are few cases where
>>>> the hardware_domain variable is checked to see if the current
>>>> domain is equal to the hardware_domain, change this cases to
>>>> use is_hardware_domain() function instead. >
>>>> Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
>>>> ---
>>>> v4 changes:
>>>> - removed unneeded check for domain NULL from is_hardware_domain
>>>> introduced in v3
>>>
>>> After this change, this patch is only avoid to open-code is_hardware_domain(). Although, it adds an extra speculation barrier.
>>>
>>> I am not against the change, however I think the commit message needs to updated to match what the patch is doing.
>>>
>>> Can you propose a new commit message?
>> Hi Julien,
>> Yes I agree, what about:
>> xen/arm: Reinforce use of is_hardware_domain
>> Among the common and arm codebase there are few cases where
>
> I would drop 'common' because you are only modifying the arm codebase.
>
>> the hardware_domain variable is checked to see if the current
>> domain is equal to the hardware_domain, change this cases to
>> use is_hardware_domain() function instead.
>
>
>> In the eventuality that hardware_domain is NULL, is_hardware_domain
>> will return false because an analysis of the common and arm codebase
>> shows that is_hardware_domain is called always with a non NULL
>> domain pointer.
>
> This paragraph seems to come out of the blue. I would drop it.
>
> How about:
>
> "
> There are a few places on Arm where we use pretty much an open-coded version of is_hardware_domain(). The main difference, is the helper will also block speculation (not yet implemented on Arm).
>
> The existing users are not in hot path, so blocking speculation would not hurt when it is implemented. So remove the open-coded version within the arm codebase.
> "
>
> If you are happy with the commit message, I will commit it the series tomorrow (to give an opportunity to Stefano to review).
>
Hi Julien,
Yes your version is much better, thank you very much!
Cheers,
Luca
> Cheers,
>
> --
> Julien Grall
next prev parent reply other threads:[~2021-04-14 13:48 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-14 9:14 [PATCH v4 0/4] xen/arm: Prevent Dom0 to be loaded when using dom0less Luca Fancellu
2021-04-14 9:14 ` [PATCH v4 1/4] xen/arm: Move dom0 creation in domain_build.c Luca Fancellu
2021-04-14 10:14 ` Bertrand Marquis
2021-04-14 9:14 ` [PATCH v4 2/4] xen/arm: Handle cases when hardware_domain is NULL Luca Fancellu
2021-04-14 10:14 ` Bertrand Marquis
2021-04-14 11:16 ` Julien Grall
2021-04-14 11:29 ` Luca Fancellu
2021-04-14 13:45 ` Julien Grall
2021-04-14 13:47 ` Luca Fancellu [this message]
2021-04-14 20:35 ` Stefano Stabellini
2021-04-15 17:17 ` Julien Grall
2021-04-14 9:14 ` [PATCH v4 3/4] xen/arm: Clarify how the domid is decided in create_domUs() Luca Fancellu
2021-04-14 10:14 ` Bertrand Marquis
2021-04-14 11:17 ` Julien Grall
2021-04-14 9:14 ` [PATCH v4 4/4] xen/arm: Prevent Dom0 to be loaded when using dom0less Luca Fancellu
2021-04-14 10:14 ` Bertrand Marquis
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