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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>,
	xen-devel <xen-devel@lists.xenproject.org>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>,
	Brian Woods <brian.woods@amd.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
	Dario Faggioli <dfaggioli@suse.com>
Subject: Re: [PATCH 6/8] x86: (command line option to) avoid use of secondary hyper-threads
Date: Thu, 12 Jul 2018 16:45:39 +0100	[thread overview]
Message-ID: <55886b2f-e5bb-c2c5-b6e5-a5d0c898b876@citrix.com> (raw)
In-Reply-To: <5B45F3C702000078001D316D@prv1-mh.provo.novell.com>

On 11/07/18 13:10, Jan Beulich wrote:
> Shared resources (L1 cache and TLB in particular) present a risk of
> information leak via side channels. Don't use hyperthreads in such
> cases, but allow independent control of their use at the same time.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> An option to avoid the up/down cycle would be to avoid clearing the
> sibling (and then perhaps also core) map of parked CPUs, allowing to
> bail early from cpu_up_helper().
>
> TBD: How to prevent the CPU from transiently becoming available for
>      scheduling when being onlined at runtime?

This looks like an argument for cancelling at call-in time, no?

> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -1040,6 +1040,13 @@ identical to the boot CPU will be parked
>  ### hpetbroadcast (x86)
>  > `= <boolean>`
>  
> +### ht (x86)

I'd suggest smt rather than ht here.  SMT is the technical term, while
HT is Intel's marketing name.

~Andrew

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  reply	other threads:[~2018-07-12 16:00 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-11 11:55 [PATCH 0/8] x86: (allow to) suppress use of hyper-threading Jan Beulich
2018-07-11 12:04 ` [PATCH 1/8] cpupools: fix state when downing a CPU failed Jan Beulich
2018-07-11 12:06 ` [PATCH 2/8] x86: distinguish CPU offlining from CPU removal Jan Beulich
2018-07-12 10:53   ` Wei Liu
2018-07-12 11:48     ` Jan Beulich
2018-07-13  8:39       ` Wei Liu
2018-07-12 12:42   ` Andrew Cooper
2018-07-11 12:06 ` [PATCH 3/8] allow cpu_down() to be called earlier Jan Beulich
2018-07-12 10:55   ` Wei Liu
2018-07-12 12:44   ` Andrew Cooper
2018-07-11 12:07 ` [PATCH 4/8] x86/AMD: distinguish compute units from hyper-threads Jan Beulich
2018-07-11 18:11   ` Brian Woods
2018-07-12 13:02   ` Andrew Cooper
2018-07-12 14:22     ` Jan Beulich
2018-07-11 12:09 ` [PATCH 5/8] x86: bring up all CPUs even if not all are supposed to be used Jan Beulich
2018-07-12 15:38   ` Andrew Cooper
2018-07-13  8:11     ` Jan Beulich
2018-07-11 12:10 ` [PATCH 6/8] x86: (command line option to) avoid use of secondary hyper-threads Jan Beulich
2018-07-12 15:45   ` Andrew Cooper [this message]
2018-07-13  8:13     ` Jan Beulich
2018-07-16 12:37       ` Andrew Cooper
2018-07-16 12:53         ` Jan Beulich
2018-07-16 13:01           ` Andrew Cooper
2018-07-11 12:11 ` [PATCH 7/8] x86/shim: fully ignore "nosmp" and "maxcpus=" Jan Beulich
2018-07-11 12:23   ` Andrew Cooper
2018-07-11 15:18   ` Roger Pau Monné
2018-07-11 16:02   ` Wei Liu
2018-07-11 12:12 ` [PATCH 8/8] cpumask: tidy {,z}alloc_cpumask_var() Jan Beulich
2018-07-11 12:20   ` Andrew Cooper
2018-07-12 15:13   ` Wei Liu
     [not found] ` <5B45F26A02000078001D312F@suse.com>
2018-07-13  9:02   ` [PATCH 1/8] cpupools: fix state when downing a CPU failed Juergen Gross
2018-07-16  9:17     ` Jan Beulich
     [not found]     ` <5B4C629002000078001D4346@suse.com>
2018-07-16 11:47       ` Juergen Gross
2018-07-16 12:19         ` Jan Beulich
     [not found]         ` <5B4C8D3702000078001D45EA@suse.com>
2018-07-16 12:47           ` Juergen Gross
2018-07-16 13:01             ` Jan Beulich
     [not found]             ` <5B4C973D02000078001D4693@suse.com>
2018-07-16 14:21               ` Juergen Gross
2018-07-16 14:26                 ` Jan Beulich
     [not found]                 ` <5B4CAB1202000078001D47BC@suse.com>
2018-07-16 14:53                   ` Juergen Gross

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