From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753090AbcD0Njr (ORCPT ); Wed, 27 Apr 2016 09:39:47 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:51499 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752610AbcD0Njp (ORCPT ); Wed, 27 Apr 2016 09:39:45 -0400 Subject: Re: [Xen-devel] [PATCH] xen/x86: actually allocate legacy interrupts on PV guests To: David Vrabel , Juergen Gross , Stefano Stabellini , Konrad Rzeszutek Wilk References: <57189880.6030102@suse.com> <572047D3.1000002@suse.com> <572087E0.4030708@citrix.com> Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org From: Boris Ostrovsky Message-ID: <5720C0E2.8080904@oracle.com> Date: Wed, 27 Apr 2016 09:38:42 -0400 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: <572087E0.4030708@citrix.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/27/2016 05:35 AM, David Vrabel wrote: > On 27/04/16 06:02, Juergen Gross wrote: >> On 21/04/16 11:30, Stefano Stabellini wrote: >>> On Thu, 21 Apr 2016, Juergen Gross wrote: >>>> On 20/04/16 15:15, Stefano Stabellini wrote: >>>>> b4ff8389ed14 is incomplete: relies on nr_legacy_irqs() to get the number >>>>> of legacy interrupts when actually nr_legacy_irqs() returns 0 after >>>>> probe_8259A(). Use NR_IRQS_LEGACY instead. >>>> Would you mind describing the resulting problem? >>> This is a good question. The symptom is: >>> >>> ata_piix: probe of 0000:00:01.1 failed with error -22 >>> >>> >>>> With this commit message I'm absolutely not capable to decide whether >>>> e.g. the other use of nr_legacy_irqs() in pci_xen_initial_domain() is >>>> correct or not. >>> I looked at it but I couldn't really test that code because if I try to >>> change the number of ioapics in the system using the "noapic" command >>> line option (which actually changes the number if ioapics, not lapics), >>> I get an error from Linux saying that noapic is not supported when >>> running on Xen. >>> >>> In my opinion having nr_legacy_irqs() calls in Xen code, which returns >>> 0, is like playing with fire. I think it would be safer/saner to replace >>> them all with NR_IRQS_LEGACY, simply because reading the code one would >>> not expect that all those loops don't actually have any iterations. >> I'm quite sure you should change both uses of nr_legacy_irqs() in >> pci_xen_initial_domain(). >> >> Looking at xen_pcifront_enable_irq() I'm not really sure what is the >> correct thing to do. >> >> Adding Konrad as he might have a better insight. > I wonder if it would be helpful to have a xen-specific #define like > XEN_NR_LEGACY_PIRQS or something, and document carefully what this means > and why it is != nr_legacy_irqs(). int xen_nr_legacy_irqs() { if (xen_hvm_domain()) return nr_legacy_irqs(); if (xen_initial_domain()) return NR_IRQS_LEGACY; return 0; } ? -boris From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [PATCH] xen/x86: actually allocate legacy interrupts on PV guests Date: Wed, 27 Apr 2016 09:38:42 -0400 Message-ID: <5720C0E2.8080904@oracle.com> References: <57189880.6030102@suse.com> <572047D3.1000002@suse.com> <572087E0.4030708@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; Format="flowed" Content-Transfer-Encoding: base64 Return-path: Received: from mail6.bemta6.messagelabs.com ([85.158.143.247]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1avPfv-0003j5-7i for xen-devel@lists.xenproject.org; Wed, 27 Apr 2016 13:38:43 +0000 In-Reply-To: <572087E0.4030708@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" To: David Vrabel , Juergen Gross , Stefano Stabellini , Konrad Rzeszutek Wilk Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org List-Id: xen-devel@lists.xenproject.org T24gMDQvMjcvMjAxNiAwNTozNSBBTSwgRGF2aWQgVnJhYmVsIHdyb3RlOgo+IE9uIDI3LzA0LzE2 IDA2OjAyLCBKdWVyZ2VuIEdyb3NzIHdyb3RlOgo+PiBPbiAyMS8wNC8xNiAxMTozMCwgU3RlZmFu byBTdGFiZWxsaW5pIHdyb3RlOgo+Pj4gT24gVGh1LCAyMSBBcHIgMjAxNiwgSnVlcmdlbiBHcm9z cyB3cm90ZToKPj4+PiBPbiAyMC8wNC8xNiAxNToxNSwgU3RlZmFubyBTdGFiZWxsaW5pIHdyb3Rl Ogo+Pj4+PiBiNGZmODM4OWVkMTQgaXMgaW5jb21wbGV0ZTogcmVsaWVzIG9uIG5yX2xlZ2FjeV9p cnFzKCkgdG8gZ2V0IHRoZSBudW1iZXIKPj4+Pj4gb2YgbGVnYWN5IGludGVycnVwdHMgd2hlbiBh Y3R1YWxseSBucl9sZWdhY3lfaXJxcygpIHJldHVybnMgMCBhZnRlcgo+Pj4+PiBwcm9iZV84MjU5 QSgpLiBVc2UgTlJfSVJRU19MRUdBQ1kgaW5zdGVhZC4KPj4+PiBXb3VsZCB5b3UgbWluZCBkZXNj cmliaW5nIHRoZSByZXN1bHRpbmcgcHJvYmxlbT8KPj4+IFRoaXMgaXMgYSBnb29kIHF1ZXN0aW9u LiBUaGUgc3ltcHRvbSBpczoKPj4+Cj4+PiBhdGFfcGlpeDogcHJvYmUgb2YgMDAwMDowMDowMS4x IGZhaWxlZCB3aXRoIGVycm9yIC0yMgo+Pj4KPj4+Cj4+Pj4gV2l0aCB0aGlzIGNvbW1pdCBtZXNz YWdlIEknbSBhYnNvbHV0ZWx5IG5vdCBjYXBhYmxlIHRvIGRlY2lkZSB3aGV0aGVyCj4+Pj4gZS5n LiB0aGUgb3RoZXIgdXNlIG9mIG5yX2xlZ2FjeV9pcnFzKCkgaW4gcGNpX3hlbl9pbml0aWFsX2Rv bWFpbigpIGlzCj4+Pj4gY29ycmVjdCBvciBub3QuCj4+PiBJIGxvb2tlZCBhdCBpdCBidXQgSSBj b3VsZG4ndCByZWFsbHkgdGVzdCB0aGF0IGNvZGUgYmVjYXVzZSBpZiBJIHRyeSB0bwo+Pj4gY2hh bmdlIHRoZSBudW1iZXIgb2YgaW9hcGljcyBpbiB0aGUgc3lzdGVtIHVzaW5nIHRoZSAibm9hcGlj IiBjb21tYW5kCj4+PiBsaW5lIG9wdGlvbiAod2hpY2ggYWN0dWFsbHkgY2hhbmdlcyB0aGUgbnVt YmVyIGlmIGlvYXBpY3MsIG5vdCBsYXBpY3MpLAo+Pj4gSSBnZXQgYW4gZXJyb3IgZnJvbSBMaW51 eCBzYXlpbmcgdGhhdCBub2FwaWMgaXMgbm90IHN1cHBvcnRlZCB3aGVuCj4+PiBydW5uaW5nIG9u IFhlbi4KPj4+Cj4+PiBJbiBteSBvcGluaW9uIGhhdmluZyBucl9sZWdhY3lfaXJxcygpIGNhbGxz IGluIFhlbiBjb2RlLCB3aGljaCByZXR1cm5zCj4+PiAwLCBpcyBsaWtlIHBsYXlpbmcgd2l0aCBm aXJlLiBJIHRoaW5rIGl0IHdvdWxkIGJlIHNhZmVyL3NhbmVyIHRvIHJlcGxhY2UKPj4+IHRoZW0g YWxsIHdpdGggTlJfSVJRU19MRUdBQ1ksIHNpbXBseSBiZWNhdXNlIHJlYWRpbmcgdGhlIGNvZGUg b25lIHdvdWxkCj4+PiBub3QgZXhwZWN0IHRoYXQgYWxsIHRob3NlIGxvb3BzIGRvbid0IGFjdHVh bGx5IGhhdmUgYW55IGl0ZXJhdGlvbnMuCj4+IEknbSBxdWl0ZSBzdXJlIHlvdSBzaG91bGQgY2hh bmdlIGJvdGggdXNlcyBvZiBucl9sZWdhY3lfaXJxcygpIGluCj4+IHBjaV94ZW5faW5pdGlhbF9k b21haW4oKS4KPj4KPj4gTG9va2luZyBhdCB4ZW5fcGNpZnJvbnRfZW5hYmxlX2lycSgpIEknbSBu b3QgcmVhbGx5IHN1cmUgd2hhdCBpcyB0aGUKPj4gY29ycmVjdCB0aGluZyB0byBkby4KPj4KPj4g QWRkaW5nIEtvbnJhZCBhcyBoZSBtaWdodCBoYXZlIGEgYmV0dGVyIGluc2lnaHQuCj4gSSB3b25k ZXIgaWYgaXQgd291bGQgYmUgaGVscGZ1bCB0byBoYXZlIGEgeGVuLXNwZWNpZmljICNkZWZpbmUg bGlrZQo+IFhFTl9OUl9MRUdBQ1lfUElSUVMgb3Igc29tZXRoaW5nLCBhbmQgZG9jdW1lbnQgY2Fy ZWZ1bGx5IHdoYXQgdGhpcyBtZWFucwo+IGFuZCB3aHkgaXQgaXMgIT0gbnJfbGVnYWN5X2lycXMo KS4KCgppbnQgeGVuX25yX2xlZ2FjeV9pcnFzKCkKewogICAgIGlmICh4ZW5faHZtX2RvbWFpbigp KQogICAgICAgICByZXR1cm4gbnJfbGVnYWN5X2lycXMoKTsKICAgICBpZiAoeGVuX2luaXRpYWxf ZG9tYWluKCkpCiAgICAgICAgIHJldHVybiBOUl9JUlFTX0xFR0FDWTsKICAgICByZXR1cm4gMDsK fQoKPwoKLWJvcmlzCgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fXwpYZW4tZGV2ZWwgbWFpbGluZyBsaXN0Clhlbi1kZXZlbEBsaXN0cy54ZW4ub3JnCmh0dHA6 Ly9saXN0cy54ZW4ub3JnL3hlbi1kZXZlbAo=