Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932711AbbKRODv (ORCPT ); Wed, 18 Nov 2015 09:03:51 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:17399 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754824AbbKRODt (ORCPT ); Wed, 18 Nov 2015 09:03:49 -0500 Subject: Re: [Xen-devel] [PATCH] xen/events: Always allocate legacy interrupts on PV guests To: Vitaly Kuznetsov , david.vrabel@citrix.com References: <1447774585-21857-1-git-send-email-boris.ostrovsky@oracle.com> <87lh9vv9pv.fsf@vitty.brq.redhat.com> Cc: konrad.wilk@oracle.com, jgross@suse.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, xen-devel@lists.xen.org From: Boris Ostrovsky Message-ID: <564C8531.2000608@oracle.com> Date: Wed, 18 Nov 2015 09:03:29 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <87lh9vv9pv.fsf@vitty.brq.redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2519 Lines: 70 On 11/18/2015 06:16 AM, Vitaly Kuznetsov wrote: > Boris Ostrovsky writes: > >> After commit 8c058b0b9c34 ("x86/irq: Probe for PIC presence before >> allocating descs for legacy IRQs") early_irq_init() will no longer >> preallocate descriptors for legacy interrupts if PIT does not >> exist. > PIC? Right. David, can you fix this before committing? > >> Therefore we need to allocate those descriptors for PV guests >> ourselves. >> >> Signed-off-by: Boris Ostrovsky >> Suggested-by: Thomas Gleixner >> --- >> drivers/xen/events/events_base.c | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c >> index 849500e..a2bb333 100644 >> --- a/drivers/xen/events/events_base.c >> +++ b/drivers/xen/events/events_base.c >> @@ -419,8 +419,8 @@ static int __must_check xen_allocate_irq_gsi(unsigned gsi) >> if (xen_pv_domain() && !xen_initial_domain()) >> return xen_allocate_irq_dynamic(); >> >> - /* Legacy IRQ descriptors are already allocated by the arch. */ >> - if (gsi < NR_IRQS_LEGACY) >> + /* On HVM legacy IRQ descriptors are already allocated by the arch. */ >> + if (xen_hvm_domain() && gsi < NR_IRQS_LEGACY) >> irq = gsi; > Wouldn't it be better to write it as > if (gsi < nr_legacy_irqs()) ? I don't think so: on PV we end up setting legacy_pic to null_legacy_pic in probe_8259A() and that will make nr_legacy_irqs() return 0. > > I think it's possible to have PIC-less HVM guests in future (btw, what > about HVMlite?). I see nr_legacy_irqs() is x86-only but it can easily be > defined to NR_IRQS_LEGACY on other arches. Yes, HVMlite (or however we will end up calling it) will allow these sorts of thing. But HVMlite is not supported yet at all. And it's x86 only. -boris > >> else >> irq = irq_alloc_desc_at(gsi, -1); >> @@ -445,8 +445,8 @@ static void xen_free_irq(unsigned irq) >> >> kfree(info); >> >> - /* Legacy IRQ descriptors are managed by the arch. */ >> - if (irq < NR_IRQS_LEGACY) >> + /* On HVM legacy IRQ descriptors are managed by the arch. */ >> + if (xen_hvm_domain() && irq < NR_IRQS_LEGACY) >> return; >> >> irq_free_desc(irq); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/