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 35761E77188 for ; Wed, 8 Jan 2025 11:27:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tVUDK-0000ST-MZ; Wed, 08 Jan 2025 06:27:06 -0500 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 1tVUDJ-0000SF-1u for qemu-devel@nongnu.org; Wed, 08 Jan 2025 06:27:05 -0500 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 1tVUDG-0000jC-7i for qemu-devel@nongnu.org; Wed, 08 Jan 2025 06:27:04 -0500 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=aWeKBmNI5YUaGHypmMBaMPOSS1NGM/osbQugEZTaQYk=; b=gLHzZhM56lK8IrZ/ea6oAKSJSX cIHehpXY8CtHXoi7IeBrnTJnlfEEyPFdRnX/smZAoSAxWjGa0J44oTBoSOlFDfLTh4OCA3C66sc2x QK/cDY+r8nUbIDzfEm97/9qYrxbdNEVtiJY1VpgUSvX7fk+Jl0dRFzoc5rKbCMcWTpghyd4cS67OY ZxWviJEECkEkElxJclSMLvjQ6058GIFFnKFBnuvwPeZI3I4OsNWcZMzjb7kqfUE6Q3wcVoMdD+HVj LLETxzbZxyjEuGyW+Ymed204Xd3h2QKQxCVZe0Q8YdEeYHewNLFMy6X6GcpJuhtMpD0Mt8mX6dh4e siYoj7QQ==; Received: from 54-240-197-238.amazon.com ([54.240.197.238] helo=u09cd745991455d.ant.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tVUDC-0000000G58Y-2WiK; Wed, 08 Jan 2025 11:26:58 +0000 Message-ID: Subject: Re: [PATCH] hw/i386/pc: Fix level interrupt sharing for Xen event channel GSI From: David Woodhouse To: Bernhard Beschow , qemu-devel@nongnu.org, "Michael S. Tsirkin" Cc: Thomas Huth , Paul Durrant , Paolo Bonzini , Richard Henderson , Eduardo Habkost , Marcel Apfelbaum Date: Wed, 08 Jan 2025 11:26:57 +0000 In-Reply-To: References: <20250107110718-mutt-send-email-mst@kernel.org> <8b2690f2c9532468fd5029d319737904b58acec2.camel@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-y28MTinlzhhHSw0hh4Wm" 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+b94846bdbc75b454f255+7808+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 --=-y28MTinlzhhHSw0hh4Wm Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2025-01-08 at 09:45 +0000, Bernhard Beschow wrote: >=20 >=20 > Am 7. Januar 2025 16:20:28 UTC schrieb David Woodhouse > : > > On Tue, 2025-01-07 at 11:07 -0500, Michael S. Tsirkin wrote: > > > On Thu, Dec 19, 2024 at 05:24:11PM +0100, David Woodhouse wrote: > > > > From: David Woodhouse > > > >=20 > > > > The system GSIs are not designed for sharing. One device might > > > > assert a > > > > shared interrupt with qemu_set_irq() and another might deassert > > > > it, and > > > > the level from the first device is lost. > > > >=20 > > > > This could be solved by using a multiplexer which functions as > > > > an OR > > > > gate, much like the PCI code already implements for > > > > pci_set_irq() for > > > > muxing the INTx lines. >=20 > Just curious: Why not use that aporoach? Could > ail.com/> > help? That looks very similar to hw/core/or-irq.c which rth pointed out to me. Is there a reason for both of them existing? It would be theoretically possible to rework the x86 GSI handling to use such a thing, yes. It would be a large yak-shaving task which exceeds the time I currently have available for a bug fix, but I don't *always* let that stop me. More to the point though, I *still* wouldn't like the outcome. I still want us to have a 'resample' callback when the interrupt is acknowledged in the interrupt controller, to see if any of the inputs still want the line to be asserted. That's the only way to handle it efficiently for VFIO INTx and for the Xen GSI callback anyway. --=-y28MTinlzhhHSw0hh4Wm 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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