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From: Jan Beulich <jbeulich@suse.com>
To: Ian Jackson <iwj@xenproject.org>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Kevin Tian" <kevin.tian@intel.com>,
	"Jun Nakajima" <jun.nakajima@intel.com>,
	"Julien Grall" <julien@xen.org>
Subject: Re: [PATCH v3 1/2][4.15] VMX: delay p2m insertion of APIC access page
Date: Mon, 22 Feb 2021 15:05:48 +0100	[thread overview]
Message-ID: <04a2869a-282f-783a-6c03-8a2d7209411a@suse.com> (raw)
In-Reply-To: <24627.38031.77928.536108@mariner.uk.xensource.com>

On 22.02.2021 12:25, Ian Jackson wrote:
> Jan Beulich writes ("[PATCH v3 1/2][4.15] VMX: delay p2m insertion of APIC access page"):
>> Inserting the mapping at domain creation time leads to a memory leak
>> when the creation fails later on and the domain uses separate CPU and
>> IOMMU page tables - the latter requires intermediate page tables to be
>> allocated, but there's no freeing of them at present in this case. Since
>> we don't need the p2m insertion to happen this early, avoid the problem
>> altogether by deferring it until the last possible point.
> 
> Thanks.
> 
>>   This comes at
>> the price of not being able to handle an error other than by crashing
>> the domain.
> 
> How worried should I be about this ?

Not overly much I would say. The difference is between a failure
(-ENOMEM) during domain creation vs the domain getting crashed
before it gets first scheduled. This is certainly less friendly
to the user, but lack of memory shouldn't typically happen when
creating domains. Plus the memory talked about here is such that
gets provided explicitly to the domain (the p2m pool), rather
than a system wide pool.

Jan


  reply	other threads:[~2021-02-22 14:06 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-22 10:55 [PATCH v3 0/2] VMX: apic access page handling adjustments Jan Beulich
2021-02-22 10:56 ` [PATCH v3 1/2][4.15] VMX: delay p2m insertion of APIC access page Jan Beulich
2021-02-22 11:25   ` Ian Jackson
2021-02-22 14:05     ` Jan Beulich [this message]
2021-02-22 17:17       ` Ian Jackson
2021-02-22 12:15   ` Roger Pau Monné
2021-02-25  8:44   ` Jan Beulich
2021-02-26  7:06     ` Tian, Kevin
2021-02-22 10:57 ` [PATCH v3 2/2] VMX: use a single, global " Jan Beulich
2021-03-01  2:34   ` Tian, Kevin
2021-03-01  8:18     ` Jan Beulich
2021-04-12 10:40 ` [PATCH v4] " Jan Beulich
2021-04-12 15:31   ` Roger Pau Monné
2021-04-13  9:24     ` Jan Beulich
2021-04-13 10:18       ` Roger Pau Monné
2021-04-13 12:03         ` Jan Beulich
2021-04-13 13:03           ` Roger Pau Monné
2021-04-17 19:24   ` Tim Deegan
2021-04-19 11:25     ` Jan Beulich
2021-04-22  7:42       ` Tim Deegan
2021-04-22  9:38         ` Jan Beulich
2021-04-22 15:05           ` Tim Deegan
2021-04-23 10:51 ` [PATCH v4 0/3] VMX APIC access page and shadow adjustments Jan Beulich
2021-04-23 10:52   ` [PATCH v4 1/3] VMX: use a single, global APIC access page Jan Beulich
2021-04-23 14:17     ` Roger Pau Monné
2021-04-23 14:42       ` Jan Beulich
2021-04-26 17:55         ` Tim Deegan
2021-04-25  1:27     ` Tian, Kevin
2021-04-26 17:53     ` Tim Deegan
2021-04-23 10:53   ` [PATCH v4 2/3] x86/shadow: re-use variables in shadow_get_page_from_l1e() Jan Beulich
2021-04-23 10:54   ` [PATCH v4 3/3] x86/shadow: streamline shadow_get_page_from_l1e() Jan Beulich
2021-04-23 11:00   ` Really v5 (was: [PATCH v4 0/3] VMX APIC access page and shadow adjustments) Jan Beulich

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