Re: [Xen-devel] [PATCH v6 5/5] domain: use PGC_extra domheap page for shared_info

From: Jan Beulich <jbeulich@suse.com>
To: Stefano Stabellini <sstabellini@kernel.org>,
	Julien Grall <julien@xen.org>
Cc: Wei Liu <wl@xen.org>,
	paul@xen.org, Andrew Cooper <andrew.cooper3@citrix.com>,
	Paul Durrant <pdurrant@amazon.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	xen-devel@lists.xenproject.org,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: Re: [Xen-devel] [PATCH v6 5/5] domain: use PGC_extra domheap page for shared_info
Date: Tue, 24 Mar 2020 10:31:26 +0100	[thread overview]
Message-ID: <391b3511-3353-e40c-858e-489389a8a3d3@suse.com> (raw)
In-Reply-To: <5d28392f-b32e-717b-636e-1aa80a75243c@suse.com>

On 24.03.2020 10:26, Jan Beulich wrote:
> On 10.03.2020 18:49, paul@xen.org wrote:
>> From: Paul Durrant <pdurrant@amazon.com>
>>
>> Currently shared_info is a shared xenheap page but shared xenheap pages
>> complicate future plans for live-update of Xen so it is desirable to,
>> where possible, not use them [1]. This patch therefore converts shared_info
>> into a PGC_extra domheap page. This does entail freeing shared_info during
>> domain_relinquish_resources() rather than domain_destroy() so care is
>> needed to avoid de-referencing a NULL shared_info pointer hence some
>> extra checks of 'is_dying' are needed.
>>
>> NOTE: For Arm, the call to free_shared_info() in arch_domain_destroy() is
>>       left in place since it is idempotent and called in the error path for
>>       arch_domain_create().
>>
>> [1] See https://lists.xenproject.org/archives/html/xen-devel/2020-02/msg02018.html
>>
>> Signed-off-by: Paul Durrant <paul@xen.org>
>> ---
>> Cc: Stefano Stabellini <sstabellini@kernel.org>
>> Cc: Julien Grall <julien@xen.org>
>> Cc: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
>> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
>> Cc: George Dunlap <george.dunlap@citrix.com>
>> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
>> Cc: Jan Beulich <jbeulich@suse.com>
>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>> Cc: Wei Liu <wl@xen.org>
>>
>> v6:
>>  - Drop dump_shared_info() but tag the shared info in the 'ExtraPage'
>>    dump
>>
>> v5:
>>  - Incorporate new dump_shared_info() function
>>
>> v2:
>>  - Addressed comments from Julien
>>  - Expanded the commit comment to explain why this patch is wanted
>> ---
>>  xen/arch/arm/domain.c      |  2 ++
> 
> Julien, Stefano? (I'd prefer to commit the entire series in one go,
> rather than leaving out just this last patch.)

Actually - never mind, I've just realized that there are still some
pending items on the last two patches of this series.

Jan