From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 13145C83F17 for ; Tue, 15 Jul 2025 08:29:09 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ubb1L-0007bS-JF; Tue, 15 Jul 2025 04:28:15 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ubb1I-0007aM-SI for qemu-devel@nongnu.org; Tue, 15 Jul 2025 04:28:13 -0400 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ubb1E-0008R0-AL for qemu-devel@nongnu.org; Tue, 15 Jul 2025 04:28:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=oHqchSoAEOxHv9loAY4ir35SZaV6y7EbYXCObSeA4bk=; b=r9sEdHEmI5uARDVKmKfkuAjahx hRC+ZRWtc3MGJ8xCsmJUc2yfMwocE9ANA24iIU7Xy7mmXrQ/AekmQaLXpDIGF+0B5Z3qPCHU1YuQA 2bjLkSNac4BvukIRmPAsrfMv534t98NkfQci1JfQOmtjCKopqV5fmOjjB/wcW/uTD1nNKxXJ3duz8 9a813FipqrgLU5rANqPJVkRnjdLsDZijVnzwBBHCexJfbEr9EphnC3fgccrqJRz7OJ23U7L5G9q4s Jkq0BRQFgj6CgHsF2ervQGdzwTMd3BN/slso57kbRh8vdbewrJGqANH7WY26Xqu6zPPTiXNVcgmzQ aJ7qoB2g==; Received: from [2001:bb6:9553:3800:3cd1:145a:abd8:186] (helo=pool-ipv6-pd.agg7.cky.chf-qkr.eir.ie) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1ubb0t-0000000BYDc-3nYd; Tue, 15 Jul 2025 08:27:47 +0000 Message-ID: <7cf6b91c1e1ea8b50d116f738215bcb55732b214.camel@infradead.org> Subject: Re: [PATCH v2] intel_iommu: Allow both Status Write and Interrupt Flag in QI wait From: David Woodhouse To: CLEMENT MATHIEU--DRIF , Konstantin Belousov Cc: Yi Liu , "Michael S. Tsirkin" , Jason Wang , Le Tan , "jhb@freebsd.org" , Marcel Apfelbaum , Paolo Bonzini , Richard Henderson , Eduardo Habkost , "qemu-devel@nongnu.org" Date: Tue, 15 Jul 2025 09:27:45 +0100 In-Reply-To: References: <0122cbabc0adcc3cf878f5fd7834d8f258c7a2f2.camel@infradead.org> <9ce8b7e6-ad15-4d2e-a430-3896eccc7519@intel.com> <4FE9A8E3-5BA5-46D3-A1FA-EA1B7C85C058@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-9VwOeGg623nlaC+DIzLQ" User-Agent: Evolution 3.52.3-0ubuntu1 MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Received-SPF: none client-ip=2001:8b0:10b:1236::1; envelope-from=BATV+4c8ff6a2891c77aa714e+7996+infradead.org+dwmw2@casper.srs.infradead.org; helo=casper.infradead.org X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --=-9VwOeGg623nlaC+DIzLQ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2025-07-15 at 06:11 +0000, CLEMENT MATHIEU--DRIF wrote: >=20 >=20 > On 14/07/2025 11:22 pm, Konstantin Belousov wrote: > > Caution: External email. Do not open attachments or click links, > > unless this email comes from a known sender and you know the > > content is safe. > >=20 > >=20 > > On Mon, Jul 14, 2025 at 05:41:22PM +0100, David Woodhouse wrote: > > > On 14 July 2025 15:28:09 GMT+01:00, Yi Liu > > > wrote: > > > > Hi David, > > > >=20 > > > > On 2025/7/14 16:00, David Woodhouse wrote: > > > > > From: David Woodhouse > > > > >=20 > > > > > FreeBSD does both, and this appears to be perfectly valid. The VT= -d > > > > > spec even talks about the ordering (the status write should be do= ne > > > > > first, unsurprisingly). >=20 > Are you talking about the ordering constraint mentioned in bullet=20 > "Page-request Drain (PD)"? >=20 No, in the v4.0 spec it's just below that bullet list, at the bottom of =C2=A76.5.2.8. The wording in =C2=A76.5.2.9 is even clearer: "The invalidation completion event interrupt must push any in-flight invalidation completion status writes, including status writes that may have originated from the same inv_wait_dsc for which the interrupt was generated." > > > > I think this "if branch" can be moved just after the inv_desc non-z= ero > > > > reserved bit checking. Hence you don't need a ret at all. :) > > >=20 > > > We want to return false if the memory write fails, and the > > > interrupt has to happen afterwards. >=20 > Per spec: "Hardware behavior is undefined if the Status Address=20 > specified is not an address route-able to memory" >=20 > Do we want to trigger the interrupt even when the DMA fails? Yes, we do. That's a quality of implementation issue. Just because the behaviour is 'undefined' and theoretically gives us permission to do whatever we like to the guest, we should still be as sensible as possible. > > >=20 > > > > btw. I'm > > > > also asking if VT-d spec allows it or not. So let's wait for a > > > > while.. Rapidly losing interest in this conversation. QEMU currently has a guest-triggerable crash, for crying out loud. I'd like to fix it and move on to finding out why FreeBSD doesn't work *even* when QEMU doesn't abort... --=-9VwOeGg623nlaC+DIzLQ Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCD9Aw ggSOMIIDdqADAgECAhAOmiw0ECVD4cWj5DqVrT9PMA0GCSqGSIb3DQEBCwUAMGUxCzAJBgNVBAYT AlVTMRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5jb20xJDAi BgNVBAMTG0RpZ2lDZXJ0IEFzc3VyZWQgSUQgUm9vdCBDQTAeFw0yNDAxMzAwMDAwMDBaFw0zMTEx MDkyMzU5NTlaMEExCzAJBgNVBAYTAkFVMRAwDgYDVQQKEwdWZXJva2V5MSAwHgYDVQQDExdWZXJv a2V5IFNlY3VyZSBFbWFpbCBHMjCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAMjvgLKj jfhCFqxYyRiW8g3cNFAvltDbK5AzcOaR7yVzVGadr4YcCVxjKrEJOgi7WEOH8rUgCNB5cTD8N/Et GfZI+LGqSv0YtNa54T9D1AWJy08ZKkWvfGGIXN9UFAPMJ6OLLH/UUEgFa+7KlrEvMUupDFGnnR06 aDJAwtycb8yXtILj+TvfhLFhafxroXrflspavejQkEiHjNjtHnwbZ+o43g0/yxjwnarGI3kgcak7 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