From: "Woods, Brian" <Brian.Woods@amd.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Woods, Brian" <Brian.Woods@amd.com>,
"Roger Pau Monné" <roger.pau@citrix.com>,
"Wei Liu" <wei.liu2@citrix.com>,
"Jan Beulich" <JBeulich@suse.com>,
Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH 4/9] x86/amd: Introduce CPUID/MSR definitions for per-vcpu SSBD support
Date: Tue, 4 Dec 2018 16:06:22 +0000 [thread overview]
Message-ID: <20181204160617.GA13738@amd.com> (raw)
In-Reply-To: <1543853902-6257-5-git-send-email-andrew.cooper3@citrix.com>
On Mon, Dec 03, 2018 at 04:18:17PM +0000, Andy Cooper wrote:
> At the time of writing, the spec is available from:
>
> https://developer.amd.com/wp-content/resources/124441_AMD64_SpeculativeStoreBypassDisable_Whitepaper_final.pdf
>
> Future hardware (Zen v2) is expect to have hardware MSR_SPEC_CTRL support,
> including SPEC_CTRL.SSBD, and with the expectation that this will be directly
> passed through to guests for performance.
>
> On currently released hardware, the only mechanism available is the legacy
> LS_CFG option, and this is very expensive to use. Furthermore, emulating
> MSR_SPEC_CTRL via interception is prohibitively expensive, as certain OSes use
> the write-discard flexibility to simplify their entry/exit logic.
>
> As an alternative, MSR_VIRT_SPEC_CTRL is specified as an architectural control
> (with semantics equivilent to MSR_SPEC_CTRL) which is provided by the
> hypervisor. This abstracts away the model-specific details of the LS_CFG
> mechanism, which allows migration safety to be retained.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewd-by: Brian Woods <brian.woods@amd.com>
--
Brian Woods
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next prev parent reply other threads:[~2018-12-04 16:06 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-03 16:18 [PATCH 0/9] xen/amd: Support for guest MSR_VIRT_SPEC_CTRL support Andrew Cooper
2018-12-03 16:18 ` [PATCH 1/9] x86/spec-ctrl: Drop the bti= command line option Andrew Cooper
2018-12-04 16:19 ` Jan Beulich
2018-12-03 16:18 ` [PATCH 2/9] x86/cpuid: Drop the synthetic X86_FEATURE_XEN_IBPB Andrew Cooper
2018-12-04 16:21 ` Jan Beulich
2018-12-03 16:18 ` [PATCH 3/9] x86/cpuid: Extend the cpuid= command line option to support all named features Andrew Cooper
2018-12-04 16:28 ` Jan Beulich
2018-12-06 12:52 ` Wei Liu
2018-12-03 16:18 ` [PATCH 4/9] x86/amd: Introduce CPUID/MSR definitions for per-vcpu SSBD support Andrew Cooper
2018-12-04 16:06 ` Woods, Brian [this message]
2018-12-05 16:39 ` Jan Beulich
2018-12-05 17:50 ` Andrew Cooper
2018-12-06 8:49 ` Jan Beulich
2018-12-06 18:35 ` Andrew Cooper
2018-12-03 16:18 ` [PATCH 5/9] x86/amd: Probe for legacy SSBD interfaces on boot Andrew Cooper
2018-12-04 16:15 ` Woods, Brian
2018-12-05 16:50 ` Jan Beulich
2018-12-05 17:09 ` Andrew Cooper
2018-12-06 8:53 ` Jan Beulich
2018-12-06 10:59 ` Jan Beulich
2018-12-28 16:30 ` Andrew Cooper
2019-01-04 8:58 ` Jan Beulich
2018-12-03 16:18 ` [PATCH 6/9] x86/amd: Allocate resources to cope with LS_CFG being per-core on Fam17h Andrew Cooper
2018-12-04 16:38 ` Woods, Brian
2018-12-05 16:57 ` Jan Beulich
2018-12-05 17:05 ` Andrew Cooper
2018-12-06 8:54 ` Jan Beulich
2018-12-06 18:46 ` Andrew Cooper
2018-12-06 19:25 ` Woods, Brian
2018-12-07 10:17 ` Jan Beulich
2018-12-03 16:18 ` [PATCH 7/9] x86/amd: Support context switching legacy SSBD interface Andrew Cooper
2018-12-04 20:27 ` Woods, Brian
2018-12-06 10:51 ` Jan Beulich
2018-12-06 18:55 ` Andrew Cooper
2018-12-07 10:25 ` Jan Beulich
2018-12-03 16:18 ` [PATCH 8/9] x86/amd: Virtualise MSR_VIRT_SPEC_CTRL for guests Andrew Cooper
2018-12-04 21:35 ` Woods, Brian
2018-12-05 8:41 ` Jan Beulich
2018-12-05 19:09 ` Andrew Cooper
2018-12-06 8:59 ` Jan Beulich
2018-12-06 19:41 ` Woods, Brian
2018-12-06 10:55 ` Jan Beulich
2018-12-03 16:18 ` [PATCH 9/9] x86/amd: Offer MSR_VIRT_SPEC_CTRL to guests Andrew Cooper
2018-12-06 10:57 ` Jan Beulich
2018-12-03 16:24 ` [PATCH 0/9] xen/amd: Support for guest MSR_VIRT_SPEC_CTRL support Jan Beulich
2018-12-03 16:31 ` Andrew Cooper
2018-12-04 9:45 ` Jan Beulich
2018-12-04 11:26 ` Andrew Cooper
2018-12-04 12:45 ` Jan Beulich
2018-12-04 13:41 ` Andrew Cooper
2018-12-04 14:07 ` Jan Beulich
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