From nobody Tue Jan 18 16:32:26 2022 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id EC4041963DAF; Tue, 18 Jan 2022 16:32:42 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4JdZ7Y38wFz4c5W; Tue, 18 Jan 2022 16:32:41 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.16.1/8.16.1) with ESMTPS id 20IGWQLV082123 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Tue, 18 Jan 2022 18:32:29 +0200 (EET) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by tom.home (8.16.1/8.16.1/Submit) id 20IGWQqk082122; Tue, 18 Jan 2022 18:32:26 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Tue, 18 Jan 2022 18:32:26 +0200 From: Konstantin Belousov To: John Baldwin Cc: Emmanuel Vadot , src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 6171e026be11 - main - bhyve: add support for MTRR Message-ID: References: <202201141142.20EBgBdI076921@gitrepo.freebsd.org> <18d89f85-7d6d-80b4-7e5a-ae3cc30f5249@FreeBSD.org> List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-all@freebsd.org X-BeenThere: dev-commits-src-all@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <18d89f85-7d6d-80b4-7e5a-ae3cc30f5249@FreeBSD.org> X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM, NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.5 X-Spam-Checker-Version: SpamAssassin 3.4.5 (2021-03-20) on tom.home X-Rspamd-Queue-Id: 4JdZ7Y38wFz4c5W X-Spamd-Bar: / Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=gmail.com (policy=none); spf=softfail (mx1.freebsd.org: 2001:470:d5e7:1::1 is neither permitted nor denied by domain of kostikbel@gmail.com) smtp.mailfrom=kostikbel@gmail.com X-Spamd-Result: default: False [0.44 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.58)[-0.575]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_FROM(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; HAS_XAW(0.00)[]; R_SPF_SOFTFAIL(0.00)[~all:c]; RCPT_COUNT_FIVE(0.00)[5]; NEURAL_SPAM_SHORT(1.00)[0.996]; NEURAL_SPAM_LONG(0.02)[0.017]; MLMMJ_DEST(0.00)[dev-commits-src-all,dev-commits-src-main]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US]; RCVD_COUNT_TWO(0.00)[2]; FREEMAIL_ENVFROM(0.00)[gmail.com]; DMARC_POLICY_SOFTFAIL(0.10)[gmail.com : No valid SPF, No valid DKIM,none] X-ThisMailContainsUnwantedMimeParts: N On Tue, Jan 18, 2022 at 07:19:15AM -0800, John Baldwin wrote: > On 1/14/22 3:42 AM, Emmanuel Vadot wrote: > > The branch main has been updated by manu: > > > > URL: https://cgit.FreeBSD.org/src/commit/?id=6171e026be11824495cebe8baf559af673a8e533 > > > > commit 6171e026be11824495cebe8baf559af673a8e533 > > Author: Corvin Köhne > > AuthorDate: 2022-01-14 09:58:48 +0000 > > Commit: Emmanuel Vadot > > CommitDate: 2022-01-14 11:41:44 +0000 > > > > bhyve: add support for MTRR > > Some guests or driver might depend on MTRR to work properly. E.g. the > > nvidia gpu driver won't work without MTRR. > > Reviewed by: markj > > MFC after: 2 weeks > > Sponsored by: Beckhoff Automation GmbH & Co. KG > > Differential Revision: https://reviews.freebsd.org/D33333 > > So this doesn't look like actual emulation, but more like a dummy version? > That is, the values aren't initialized to the "normal" state (WB for guest RAM, > UC- for everything else), and the state isn't enforced in any way (I think the > only sane way to actually implement these would be to use MTRR to set PAT values > in EPT entries if EPT even supports PAT). Perhaps this mostly doesn't matter > since we don't directly map BARs in EPT anyway? (Though perhaps for passthrough > we might in which case you'd want to honor these settings in those?) > I do not believe that it is safe to enable actual application of the cache modes set by guest, to the EPT pages. At very least, there are a lot of erratas claiming broken situations like inconsistent mappings modes causing machine checks or reboots on Intel processors. Or, it should be only enabled for specific trusted vms. For passthough, I think we only need to set proper mode for BARs in EPT in advance.