From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>
Subject: Re: [PATCH v4 2/4] x86/spec-ctrl: defer context-switch IBPB until guest entry
Date: Mon, 18 Dec 2023 13:39:06 +0100 [thread overview]
Message-ID: <ZYA9ap4dB5nnFCu3@macbook> (raw)
In-Reply-To: <83c2a504-bce4-d3e7-1d9a-76ac0ca17bab@suse.com>
On Tue, Feb 14, 2023 at 05:11:05PM +0100, Jan Beulich wrote:
> In order to avoid clobbering Xen's own predictions, defer the barrier as
> much as possible. Merely mark the CPU as needing a barrier issued the
> next time we're exiting to guest context.
While I understand that doing the flush in the middle of the guest
context might not be ideal, as it's my understanding we also
needlessly flush Xen predictions, I'm unsure whether this makes any
difference in practice, and IMO just makes the exit to guest paths
more complex.
Thanks, Roger.
next prev parent reply other threads:[~2023-12-18 12:39 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-14 16:09 [PATCH v4 0/4 + v1 0/1] x86/spec-ctrl: IBPB improvements Jan Beulich
2023-02-14 16:10 ` [PATCH v4 1/4] x86/spec-ctrl: add logic to issue IBPB on exit to guest Jan Beulich
2023-12-18 12:11 ` Roger Pau Monné
2023-12-18 13:46 ` Jan Beulich
2023-12-18 13:50 ` Jan Beulich
2023-12-18 15:43 ` Roger Pau Monné
2023-12-18 16:02 ` Jan Beulich
2023-12-18 13:54 ` Jan Beulich
2023-12-18 15:40 ` Roger Pau Monné
2023-12-18 16:00 ` Jan Beulich
2023-02-14 16:11 ` [PATCH v4 2/4] x86/spec-ctrl: defer context-switch IBPB until guest entry Jan Beulich
2023-12-18 12:39 ` Roger Pau Monné [this message]
2023-12-18 13:58 ` Jan Beulich
2023-12-18 17:27 ` Roger Pau Monné
2023-02-14 16:11 ` [PATCH v4 3/4] x86: limit issuing of IBPB during context switch Jan Beulich
2023-12-18 15:19 ` Roger Pau Monné
2023-12-18 16:09 ` Jan Beulich
2023-12-18 16:11 ` Jan Beulich
2023-02-14 16:12 ` [PATCH v4 4/4] x86/PV: issue branch prediction barrier when switching 64-bit guest to kernel mode Jan Beulich
2023-12-18 17:24 ` Roger Pau Monné
2023-12-19 9:56 ` Jan Beulich
2023-12-19 11:48 ` Roger Pau Monné
2023-12-19 14:06 ` Jan Beulich
2023-12-19 15:11 ` Roger Pau Monné
2023-12-19 17:07 ` Roger Pau Monné
2023-12-20 9:25 ` Jan Beulich
2023-12-20 9:59 ` Roger Pau Monné
2023-02-14 16:13 ` [PATCH] x86/Xen: make use of IBPB controlling VM assist Jan Beulich
2023-02-14 23:53 ` Boris Ostrovsky
2023-02-15 0:07 ` Boris Ostrovsky
2023-02-15 8:31 ` Jan Beulich
2023-02-15 23:22 ` Boris Ostrovsky
2023-02-16 7:33 ` Jan Beulich
2023-03-17 13:56 ` Juergen Gross
2023-03-17 14:21 ` Andrew Cooper
2023-03-17 14:28 ` Juergen Gross
2023-03-20 10:21 ` Jan Beulich
2023-03-20 10:19 ` Jan Beulich
2023-03-20 13:02 ` Juergen Gross
2023-03-20 13:17 ` Jan Beulich
2023-03-20 13:35 ` Juergen Gross
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