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Fri, 20 Nov 2020 10:00:07 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id f64c7928-8212-47e3-a3d8-6aa5b63871e5; Fri, 20 Nov 2020 10:00:05 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9E5DCAC23; Fri, 20 Nov 2020 10:00:04 +0000 (UTC) Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kg3D5-0008RY-F4 for xen-devel@lists.xenproject.org; Fri, 20 Nov 2020 10:00:07 +0000 X-Inumbo-ID: f64c7928-8212-47e3-a3d8-6aa5b63871e5 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id f64c7928-8212-47e3-a3d8-6aa5b63871e5; Fri, 20 Nov 2020 10:00:05 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1605866404; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DmQ50/yXucWRgzVb9oJHTNHg7jZGOFcFMa1qRlKGoU8=; b=gzBCRV4iLy876FLKWdxwyEpk9QxqdmDDaZvz7qw4JBESbSV+6S9Jn6ASJCq0Qu5HvDEjyX FQZJsFFti8PtqbSz6Bbo4O6v1ssNAUwU4M47efX81f8VwAbHuzktJDUTvwpYMrNbM9QUcS 7R5ykfC3QstSPwsc8ZZbSBiQCs3j6s0= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9E5DCAC23; Fri, 20 Nov 2020 10:00:04 +0000 (UTC) Subject: Re: NetBSD dom0 PVH: hardware interrupts stalls To: Manuel Bouyer Cc: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , xen-devel@lists.xenproject.org References: <20201118143928.hvamuf7t7jycsrzb@Air-de-Roger> <20201119141915.igyb7djkw47rf2dt@Air-de-Roger> <20201119155718.GB4104@antioche.eu.org> <20201119165734.GA4903@antioche.eu.org> <20201119175733.GA6067@antioche.eu.org> <1a50e1e2-b69c-afd6-a179-316231512004@suse.com> <20201120082855.5z4cibcd5djlwmgp@Air-de-Roger> <20201120085249.GA1508@antioche.eu.org> <97f371a9-00fe-33fe-8923-c247f44f9af6@suse.com> <20201120092754.GH1508@antioche.eu.org> From: Jan Beulich Message-ID: <20904a6a-ac64-755d-d228-4c49faf66fb5@suse.com> Date: Fri, 20 Nov 2020 11:00:05 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.3 MIME-Version: 1.0 In-Reply-To: <20201120092754.GH1508@antioche.eu.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 20.11.2020 10:27, Manuel Bouyer wrote: > On Fri, Nov 20, 2020 at 09:59:57AM +0100, Jan Beulich wrote: >> Well, anything coming through the LAPIC needs ack-ing (except for >> the spurious interrupt of course), or else ISR won't get updated >> and further interrupts at this or lower priority can't be serviced >> (delivered) anymore. This includes interrupts originally coming >> through the IO-APIC. But the same constraint / requirement exists >> on baremetal. > > OK, so even if I didn't see where this happens, it's happening. > Is it what's Xen is using as ACK from the dom0 for a IOAPIC > interrupt, or is it something else (at the IOAPIC level) ? It's the traditional LAPIC based EOI mechanism that Xen intercepts (as necessary) on the guest side and then translates (via surprisingly many layers of calls) into the necessary EOI / unmask / whatever at the hardware level. Our vIO-APIC implementation so far doesn't support IO-APIC based EOI at all (which is reflected in the IO-APIC version ID being 0x11). Jan