From: Jan Beulich <jbeulich@suse.com>
To: "Jürgen Groß" <jgross@suse.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>, "Wei Liu" <wl@xen.org>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Paul Durrant" <pdurrant@amazon.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v2] x86 / iommu: set up a scratch page in the quarantine domain
Date: Tue, 10 Dec 2019 09:57:31 +0100 [thread overview]
Message-ID: <72311af3-e47a-c868-fa47-89a74b043a4c@suse.com> (raw)
In-Reply-To: <920f4319-ed07-687c-a569-ab20faeda2a8@suse.com>
On 10.12.2019 09:12, Jürgen Groß wrote:
> On 10.12.19 09:05, Jan Beulich wrote:
>> On 10.12.2019 08:16, Tian, Kevin wrote:
>>> While the quarantine idea sounds good overall, I'm still not convinced
>>> to have it the only way in place just for handling some known-buggy
>>> device. It kills the possibility of identifying a new buggy device and then
>>> deciding not to use it in the first space... I thought about whether it
>>> will get better when future IOMMU implements A/D bit - by checking
>>> access bit being set then we'll know some buggy device exists, but,
>>> the scratch page is shared by all devices then we cannot rely on this
>>> feature to find out the actual buggy one.
>>
>> Thinking about it - yes, I think I agree. This (as with so many
>> workarounds) would better be an off-by-default one. The main issue
>> I understand this would have is that buggy systems then might hang
>> without even having managed to get a log message out - Paul?
>>
>> Jürgen - would you be amenable to an almost last minute refinement
>> here (would then also need to still be backported to 4.12.2, or
>> the original backport reverted, to avoid giving the impression of
>> a regression)?
>
> So what is your suggestion here? To have a boot option (defaulting to
> off) for enabling the scratch page?
Yes (and despite having seen Paul's reply).
Jan
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next prev parent reply other threads:[~2019-12-10 8:57 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 17:11 [Xen-devel] [PATCH v2] x86 / iommu: set up a scratch page in the quarantine domain Paul Durrant
2019-11-28 11:17 ` Jan Beulich
2019-11-28 11:32 ` Jürgen Groß
2019-12-03 9:36 ` Jan Beulich
2019-12-10 7:16 ` Tian, Kevin
2019-12-10 8:05 ` Jan Beulich
2019-12-10 8:12 ` Jürgen Groß
2019-12-10 8:19 ` Durrant, Paul
2019-12-10 8:57 ` Jan Beulich [this message]
2019-12-10 9:07 ` Jürgen Groß
2019-12-10 9:16 ` Durrant, Paul
2019-12-10 9:44 ` Jan Beulich
2019-12-10 10:19 ` Durrant, Paul
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