From: Jan Beulich <jbeulich@suse.com>
To: Juergen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org, x86@kernel.org,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH 0/3] xen: remove some checks for always present Xen features
Date: Thu, 22 Apr 2021 17:23:53 +0200 [thread overview]
Message-ID: <08e3fcf1-dabc-c550-f76c-47a78a12274b@suse.com> (raw)
In-Reply-To: <b69df7d3-6fcb-a565-9ec5-a272b6163320@suse.com>
On 22.04.2021 17:17, Juergen Gross wrote:
> On 22.04.21 17:16, Jan Beulich wrote:
>> On 22.04.2021 17:10, Juergen Gross wrote:
>>> Some features of Xen can be assumed to be always present, so add a
>>> central check to verify this being true and remove the other checks.
>>>
>>> Juergen Gross (3):
>>> xen: check required Xen features
>>> xen: assume XENFEAT_mmu_pt_update_preserve_ad being set for pv guests
>>> xen: assume XENFEAT_gnttab_map_avail_bits being set for pv guests
>>
>> I wonder whether it's a good idea to infer feature presence from
>> version numbers. If (at some point in the past) you had inferred
>> gnttab v2 being available by version, this would have been broken
>> by its availability becoming controllable by a command line option
>> in Xen.
>
> I'm testing the feature to be really present when booting and issue a
> message if it is not there.
And how does this help if the feature really isn't there yet other code
assumes it is?
Jan
next prev parent reply other threads:[~2021-04-22 15:24 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 15:10 [PATCH 0/3] xen: remove some checks for always present Xen features Juergen Gross
2021-04-22 15:10 ` [PATCH 1/3] xen: check required " Juergen Gross
2021-04-22 15:26 ` Stefano Stabellini
2021-04-22 15:32 ` Juergen Gross
2021-05-10 12:11 ` Boris Ostrovsky
2021-05-10 13:21 ` Juergen Gross
2021-04-22 15:10 ` [PATCH 2/3] xen: assume XENFEAT_mmu_pt_update_preserve_ad being set for pv guests Juergen Gross
2021-04-22 15:10 ` [PATCH 3/3] xen: assume XENFEAT_gnttab_map_avail_bits " Juergen Gross
2021-04-22 15:16 ` [PATCH 0/3] xen: remove some checks for always present Xen features Jan Beulich
2021-04-22 15:17 ` Juergen Gross
2021-04-22 15:23 ` Jan Beulich [this message]
2021-04-22 15:28 ` Juergen Gross
2021-04-22 15:42 ` Jan Beulich
2021-04-22 15:49 ` Juergen Gross
2021-04-22 15:51 ` Andrew Cooper
2021-05-10 7:34 ` Juergen Gross
2021-05-10 11:31 ` Peter Zijlstra
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