From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34095) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WK7fS-0004yY-FM for qemu-devel@nongnu.org; Sun, 02 Mar 2014 09:47:07 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WK7fN-00077t-I4 for qemu-devel@nongnu.org; Sun, 02 Mar 2014 09:47:02 -0500 Received: from mx1.redhat.com ([209.132.183.28]:8263) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WK7fN-00076p-7c for qemu-devel@nongnu.org; Sun, 02 Mar 2014 09:46:57 -0500 Date: Sun, 2 Mar 2014 16:52:22 +0200 From: "Michael S. Tsirkin" Message-ID: <20140302145222.GE30372@redhat.com> References: <20140228172343.GI17184@ERROL.INI.CMU.EDU> <20140228185719.GJ17184@ERROL.INI.CMU.EDU> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140228185719.GJ17184@ERROL.INI.CMU.EDU> Subject: Re: [Qemu-devel] [RFC PATCH v2] qemu: x86: ignore ioapic polarity List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Gabriel L. Somlo" Cc: pbonzini@redhat.com, qemu-devel@nongnu.org, agraf@suse.de On Fri, Feb 28, 2014 at 01:57:19PM -0500, Gabriel L. Somlo wrote: > Both QEMU and KVM have already accumulated a significant number of > optimizations based on the hard-coded assumption that ioapic polarity > will always use the ActiveHigh convention, where the logical and > physical states of level-triggered irq lines always match (i.e., > active(asserted) == high == 1, inactive == low == 0). QEMU guests > are expected to follow directions given via ACPI and configure the > ioapic with polarity 0 (ActiveHigh). However, even when misbehaving > guests (e.g. OS X <= 10.9) set the ioapic polarity to 1 (ActiveLow), > QEMU will still use the ActiveHigh signaling convention when > interfacing with the emulated ioapic. > > This patch modifies the emulated ioapic to completely ignore polarity > as set by the guest OS, enabling misbehaving guests to work alongside > those which comply with the ActiveHigh polarity specified by QEMU's > ACPI tables. > > Signed-off-by: Gabriel L. Somlo Acked-by: Michael S. Tsirkin Reviewed-by: Michael S. Tsirkin With this, we should be able to change ACPI to specify active-low, which is closer to what real hardware does. But as long as we don't I think there's no need for compatibility with old machine types: we are not breaking any behaviour that wasn't already broken. > --- > > > OK, this would "harmonize" TCG with KVM, in terms of acknowledging > > the realities of hard-coded ActiveHigh behavior throughout the rest > > of the code base. > > Now with a new and improved commit blurb :) > > Thanks, > Gabriel > > hw/intc/ioapic.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c > index 652dd47..b527932 100644 > --- a/hw/intc/ioapic.c > +++ b/hw/intc/ioapic.c > @@ -93,9 +93,6 @@ static void ioapic_set_irq(void *opaque, int vector, int level) > uint32_t mask = 1 << vector; > uint64_t entry = s->ioredtbl[vector]; > > - if (entry & (1 << IOAPIC_LVT_POLARITY_SHIFT)) { > - level = !level; > - } > if (((entry >> IOAPIC_LVT_TRIGGER_MODE_SHIFT) & 1) == > IOAPIC_TRIGGER_LEVEL) { > /* level triggered */ > -- > 1.8.1.4