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Wed, 24 Jun 2020 14:23:59 +0200 (CEST) Received: from belindir.nask.net.pl (belindir.nask.net.pl [172.16.10.10]) by belindir.nask.net.pl (Postfix) with ESMTP id E5782200F2; Wed, 24 Jun 2020 14:23:59 +0200 (CEST) Date: Wed, 24 Jun 2020 14:23:59 +0200 (CEST) From: =?utf-8?Q?Micha=C5=82_Leszczy=C5=84ski?= To: Andrew Cooper Message-ID: <1353594139.12442277.1593001439838.JavaMail.zimbra@cert.pl> In-Reply-To: References: <122238637.9820857.1592523264685.JavaMail.zimbra@cert.pl> <800738193.11403725.1592836530558.JavaMail.zimbra@cert.pl> <87576264-e7df-2590-f141-351d76baac7a@suse.com> <1130937743.11428389.1592841763323.JavaMail.zimbra@cert.pl> <5b7dd58f-2dc1-32bc-3add-d896631734a4@suse.com> <901046162.11470361.1592874264410.JavaMail.zimbra@cert.pl> <32b7234b-dc64-a0ea-2c5c-448bcec44c34@suse.com> Subject: Re: [PATCH v2 4/7] x86/vmx: add do_vmtrace_op MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [172.16.10.10] X-Mailer: Zimbra 8.6.0_GA_1194 (ZimbraWebClient - GC83 (Win)/8.6.0_GA_1194) Thread-Topic: x86/vmx: add do_vmtrace_op Thread-Index: o6iyDlCcFKtukIq7gCjwJRc2Z2TpEA== X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Kevin Tian , Stefano Stabellini , Julien Grall , Jun Nakajima , Wei Liu , Tamas K Lengyel , Ian Jackson , George Dunlap , "Kang, Luwei" , Jan Beulich , Xen-devel , Roger Pau =?utf-8?Q?Monn=C3=A9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" ----- 23 cze 2020 o 19:24, Andrew Cooper andrew.cooper3@citrix.com napisa= =C5=82(a): > On 23/06/2020 09:51, Jan Beulich wrote: >> I'd still like to see an explicit confirmation by him that this >> use of memory is indeed what he has intended. There are much smaller >> amounts of memory which we allocate on demand, just to avoid >> allocating some without then ever using it. >=20 > PT is a debug/diagnostic tool.=C2=A0 Its not something you'd run in > production against a production VM. >=20 > It's off by default (by virtue of having to explicitly ask to use it in > the first place), and those who've asked for it don't want to be finding > -ENOMEM after the domain has been running for a few seconds (or midway > through the vcpus), when they inveterately want to map the rings. >=20 > Those who request buffers in the first place and forget about them are > not semantically different from those who ask for a silly shadow memory > limit, or typo the guest memory and give it too much.=C2=A0 Its a admin > error, not a safety/correctness issue. >=20 > ~Andrew Absolutely +1. Assuming that somebody wants to perform some advanced scenario and is tryin= g to run many domains (e.g. 20), it's much better to have 19 domains working fine and 1 prematurely crashing because of -ENOMEM, rather than have all 20 domains randomly crashing in runtime because it turned out there is a shortage of memory. Best regards, Micha=C5=82 Leszczy=C5=84ski CERT Polska