From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: keir@xen.org, Ian.Campbell@citrix.com,
stefano.stabellini@eu.citrix.com, George.Dunlap@eu.citrix.com,
Ian.Jackson@eu.citrix.com, xen-devel@lists.xen.org,
Chao Peng <chao.p.peng@linux.intel.com>,
dgdegra@tycho.nsa.gov
Subject: Re: [PATCH v15 01/11] multicall: add no preemption ability between two calls
Date: Wed, 10 Sep 2014 11:07:29 +0100 [thread overview]
Message-ID: <54103F01020000780003328F@mail.emea.novell.com> (raw)
In-Reply-To: <54101D29.8010606@citrix.com>
>>> On 10.09.14 at 11:43, <andrew.cooper3@citrix.com> wrote:
> Actually, on further thought, using multicalls like this cannot possibly
> be correct from a functional point of view.
>
> Even with the no preempt flag between a wrmsr/rdmsr hypercall pair,
> there is no guarantee that accesses to remote cpus msrs won't interleave
> with a different natural access, clobbering the results of the wrmsr.
>
> However this is solved, the wrmsr/rdmsr pair *must* be part of the same
> synchronous thread of execution on the appropriate cpu. You can trust
> that interrupts won't play with these msrs, but you absolutely can't
> guarantee that IPI/wrmsr/IPI/rdmsr will work.
Not sure I follow, particularly in the context of the white listing of
MSRs permitted here (which ought to not include anything the
hypervisor needs control over).
Jan
next prev parent reply other threads:[~2014-09-10 10:07 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-05 8:37 [PATCH v15 00/11] enable Cache QoS Monitoring (CQM) feature Chao Peng
2014-09-05 8:37 ` [PATCH v15 01/11] multicall: add no preemption ability between two calls Chao Peng
2014-09-05 10:46 ` Andrew Cooper
2014-09-09 6:43 ` Chao Peng
2014-09-09 10:39 ` Jan Beulich
2014-09-09 10:51 ` Andrew Cooper
2014-09-09 11:51 ` Jan Beulich
2014-09-09 12:44 ` Andrew Cooper
2014-09-09 13:15 ` Jan Beulich
2014-09-10 1:32 ` Chao Peng
2014-09-10 9:43 ` Andrew Cooper
2014-09-10 10:07 ` Jan Beulich [this message]
2014-09-10 10:15 ` Andrew Cooper
2014-09-10 10:25 ` Jan Beulich
2014-09-10 11:12 ` Andrew Cooper
2014-09-12 2:55 ` Chao Peng
2014-09-17 9:22 ` Chao Peng
2014-09-17 9:44 ` Jan Beulich
2014-09-18 13:45 ` Chao Peng
2014-09-18 14:22 ` Jan Beulich
2014-09-05 8:37 ` [PATCH v15 02/11] x86: add generic resource (e.g. MSR) access hypercall Chao Peng
2014-09-05 10:59 ` Andrew Cooper
2014-09-05 11:49 ` Jan Beulich
2014-09-10 2:55 ` Chao Peng
2014-09-29 18:52 ` Konrad Rzeszutek Wilk
2014-09-30 7:45 ` Jan Beulich
2014-09-05 8:37 ` [PATCH v15 03/11] xsm: add resource operation related xsm policy Chao Peng
2014-09-05 8:37 ` [PATCH v15 04/11] tools: provide interface for generic resource access Chao Peng
2014-09-05 8:37 ` [PATCH v15 05/11] x86: detect and initialize Platform QoS Monitoring feature Chao Peng
2014-09-05 11:05 ` Andrew Cooper
2014-09-05 8:37 ` [PATCH v15 06/11] x86: dynamically attach/detach QoS monitoring service for a guest Chao Peng
2014-09-05 8:37 ` [PATCH v15 07/11] x86: collect global QoS monitoring information Chao Peng
2014-09-05 8:37 ` [PATCH v15 08/11] x86: enable QoS monitoring for each domain RMID Chao Peng
2014-09-05 8:37 ` [PATCH v15 09/11] x86: add QoS monitoring related MSRs in allowed list Chao Peng
2014-09-05 8:37 ` [PATCH v15 10/11] xsm: add platform QoS related xsm policies Chao Peng
2014-09-05 8:37 ` [PATCH v15 11/11] tools: CMDs and APIs for Platform QoS Monitoring Chao Peng
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