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From: "Woods, Brian" <Brian.Woods@amd.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Wei Liu" <wei.liu2@citrix.com>,
	"Jan Beulich" <JBeulich@suse.com>,
	"Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>,
	Xen-devel <xen-devel@lists.xenproject.org>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Woods, Brian" <Brian.Woods@amd.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH] x86/svm: Drop support for AMD's Lightweight Profiling
Date: Mon, 20 May 2019 18:43:10 +0000	[thread overview]
Message-ID: <20190520184306.GC23047@amd.com> (raw)
In-Reply-To: <1558347216-19179-1-git-send-email-andrew.cooper3@citrix.com>

On Mon, May 20, 2019 at 11:13:36AM +0100, Andy Cooper wrote:
> Lightweight Profiling was introduced in Bulldozer (Fam15h), but was dropped
> from Zen (Fam17h) processors.  Furthermore, LWP was dropped from Fam15/16 CPUs
> when IBPB for Spectre v2 was introduced in microcode, owing to LWP not being
> used in practice.
> 
> As a result, CPUs which are operating within specification (i.e. with up to
> date microcode) no longer have this feature, and therefore are not using it.
> 
> Drop support from Xen.  The main motivation here is to remove unnecessary
> complexity from CPUID handling, but it also tidies up the SVM code nicely.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Brian Woods <brian.woods@amd.com>

I've confirmed with HW engineers that it's going away.

-- 
Brian Woods

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

WARNING: multiple messages have this Message-ID (diff)
From: "Woods, Brian" <Brian.Woods@amd.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Wei Liu" <wei.liu2@citrix.com>,
	"Jan Beulich" <JBeulich@suse.com>,
	"Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>,
	Xen-devel <xen-devel@lists.xenproject.org>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Woods, Brian" <Brian.Woods@amd.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH] x86/svm: Drop support for AMD's Lightweight Profiling
Date: Mon, 20 May 2019 18:43:10 +0000	[thread overview]
Message-ID: <20190520184306.GC23047@amd.com> (raw)
Message-ID: <20190520184310.77x0D7ZdwwmqOtNKg2xHvVCrWw9Faa85ruC_8Hl-GXw@z> (raw)
In-Reply-To: <1558347216-19179-1-git-send-email-andrew.cooper3@citrix.com>

On Mon, May 20, 2019 at 11:13:36AM +0100, Andy Cooper wrote:
> Lightweight Profiling was introduced in Bulldozer (Fam15h), but was dropped
> from Zen (Fam17h) processors.  Furthermore, LWP was dropped from Fam15/16 CPUs
> when IBPB for Spectre v2 was introduced in microcode, owing to LWP not being
> used in practice.
> 
> As a result, CPUs which are operating within specification (i.e. with up to
> date microcode) no longer have this feature, and therefore are not using it.
> 
> Drop support from Xen.  The main motivation here is to remove unnecessary
> complexity from CPUID handling, but it also tidies up the SVM code nicely.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Brian Woods <brian.woods@amd.com>

I've confirmed with HW engineers that it's going away.

-- 
Brian Woods

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

  parent reply	other threads:[~2019-05-20 18:43 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20 10:13 [PATCH] x86/svm: Drop support for AMD's Lightweight Profiling Andrew Cooper
2019-05-20 10:13 ` [Xen-devel] " Andrew Cooper
2019-05-20 11:40 ` Jan Beulich
2019-05-20 11:40   ` [Xen-devel] " Jan Beulich
2019-05-20 12:30   ` Andrew Cooper
2019-05-20 12:30     ` [Xen-devel] " Andrew Cooper
2019-05-20 18:43 ` Woods, Brian [this message]
2019-05-20 18:43   ` Woods, Brian

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