From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>,
Xen-devel <xen-devel@lists.xen.org>,
Brian Woods <brian.woods@amd.com>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [PATCH 5/9] x86/amd: Probe for legacy SSBD interfaces on boot
Date: Thu, 06 Dec 2018 01:53:11 -0700 [thread overview]
Message-ID: <5C08E37702000078002036DD@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <b2df3212-f972-fea6-64d5-aced5ead2f0d@citrix.com>
>>> On 05.12.18 at 18:09, <andrew.cooper3@citrix.com> wrote:
> On 05/12/2018 16:50, Jan Beulich wrote:
>>
>>> --- a/xen/include/asm-x86/cpufeatures.h
>>> +++ b/xen/include/asm-x86/cpufeatures.h
>>> @@ -25,6 +25,7 @@ XEN_CPUFEATURE(XEN_SMAP, (FSCAPINTS+0)*32+11) /* SMAP gets used by Xen it
>>> XEN_CPUFEATURE(LFENCE_DISPATCH, (FSCAPINTS+0)*32+12) /* lfence set as Dispatch Serialising */
>>> XEN_CPUFEATURE(IND_THUNK_LFENCE,(FSCAPINTS+0)*32+13) /* Use IND_THUNK_LFENCE */
>>> XEN_CPUFEATURE(IND_THUNK_JMP, (FSCAPINTS+0)*32+14) /* Use IND_THUNK_JMP */
>>> +XEN_CPUFEATURE(LEGACY_SSBD, (FSCAPINTS+0)*32+15) /* LS_CFG or VIRT_SPEC_CTRL available for SSBD */
>> ... here, but I still will need to see how this gets used before
>> giving my ack here. Additionally I can see "legacy" as a suitable
>> name for the LS_CFG approach, but does this also fit the
>> VIRT_SPEC_CTRL one?
>
> In practice, VIRT_SPEC_CTRL means "your hypervisor is using LS_CFG on
> your behalf".
>
> As to the joint meaning, that's because it is the most appropriate (i.e.
> simple) way to structure the code.
Synthetic feature bits, other than simple boolean variables, are
mainly (if not exclusively) meant to allow keying off of them
alternatives patching. For two different approaches like the
ones here this seems unlikely to be the goal, but since I didn't
make it to the end of the series yet, I didn't want to judge early.
Jan
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next prev parent reply other threads:[~2018-12-06 8:53 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
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 [this message]
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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