Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755568AbcDLCIv (ORCPT ); Mon, 11 Apr 2016 22:08:51 -0400 Received: from mail.kernel.org ([198.145.29.136]:59546 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750953AbcDLCIu (ORCPT ); Mon, 11 Apr 2016 22:08:50 -0400 Date: Mon, 11 Apr 2016 19:08:40 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-X260 To: Vitaly Kuznetsov cc: x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Jiang Liu , "K. Y. Srinivasan" , linux-kernel@vger.kernel.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, david.vrabel@citrix.com, sstabellini@kernel.org, jgross@suse.com Subject: Xen regression, Was: [PATCH] x86/irq: Probe for PIC presence before allocating descs for legacy IRQs In-Reply-To: <1446470676-1877-1-git-send-email-vkuznets@redhat.com> Message-ID: References: <1446470676-1877-1-git-send-email-vkuznets@redhat.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4942 Lines: 144 Hi all, Unfortunately this patch (now commit 8c058b0b9c34d8c8d7912880956543769323e2d8) causes a regression on Xen when running on top of QEMU: the number of PIT irqs get set to 0 by probe_8259A but actually there are 16. Any suggestions on how to fix this? 1) we could revert 8c058b0b9c34d8c8d7912880956543769323e2d8 2) we could introduce an 'if (!xen_domain())' in probe_8259A 3) suggestions welcome On Mon, 2 Nov 2015, Vitaly Kuznetsov wrote: > Commit d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain > interfaces") brought a regression for Hyper-V Gen2 instances. These > instances don't have i8259 legacy PIC but they use legacy IRQs for serial > port, rtc, and acpi. With this commit included we end up with these IRQs > not initialized. Earlier, there was a special workaround for legacy IRQs > in mp_map_pin_to_irq() doing mp_irqdomain_map() without looking at > nr_legacy_irqs() and now we fail in __irq_domain_alloc_irqs() when > irq_domain_alloc_descs() returns -EEXIST. > > The essence of the issue seems to be that early_irq_init() calls > arch_probe_nr_irqs() to figure out the number of legacy IRQs before > we probe for i8259 and gets 16. Later when init_8259A() is called we switch > to NULL legacy PIC and nr_legacy_irqs() starts to return 0 but we already > have 16 descs allocated. > > Solve the issue by separating i8259 probe from init and calling it in > arch_probe_nr_irqs() before we actually use nr_legacy_irqs() information. > > Fixes: d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain interfaces") > Signed-off-by: Vitaly Kuznetsov > --- > arch/x86/include/asm/i8259.h | 1 + > arch/x86/kernel/apic/vector.c | 3 +++ > arch/x86/kernel/i8259.c | 24 ++++++++++++++++-------- > 3 files changed, 20 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/include/asm/i8259.h b/arch/x86/include/asm/i8259.h > index ccffa53..bd55a77 100644 > --- a/arch/x86/include/asm/i8259.h > +++ b/arch/x86/include/asm/i8259.h > @@ -60,6 +60,7 @@ struct legacy_pic { > void (*mask_all)(void); > void (*restore_mask)(void); > void (*init)(int auto_eoi); > + void (*probe)(void); > int (*irq_pending)(unsigned int irq); > void (*make_irq)(unsigned int irq); > }; > diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c > index 836d11b..aadd7ae 100644 > --- a/arch/x86/kernel/apic/vector.c > +++ b/arch/x86/kernel/apic/vector.c > @@ -361,6 +361,9 @@ int __init arch_probe_nr_irqs(void) > if (nr < nr_irqs) > nr_irqs = nr; > > + /* nr_legecy_irqs() depends on the PIC presence */ > + legacy_pic->probe(); > + > return nr_legacy_irqs(); > } > > diff --git a/arch/x86/kernel/i8259.c b/arch/x86/kernel/i8259.c > index 16cb827..96f1562 100644 > --- a/arch/x86/kernel/i8259.c > +++ b/arch/x86/kernel/i8259.c > @@ -295,16 +295,11 @@ static void unmask_8259A(void) > raw_spin_unlock_irqrestore(&i8259A_lock, flags); > } > > -static void init_8259A(int auto_eoi) > +static void probe_8259A(void) > { > unsigned long flags; > unsigned char probe_val = ~(1 << PIC_CASCADE_IR); > unsigned char new_val; > - > - i8259A_auto_eoi = auto_eoi; > - > - raw_spin_lock_irqsave(&i8259A_lock, flags); > - > /* > * Check to see if we have a PIC. > * Mask all except the cascade and read > @@ -312,16 +307,27 @@ static void init_8259A(int auto_eoi) > * have a PIC, we will read 0xff as opposed to the > * value we wrote. > */ > + raw_spin_lock_irqsave(&i8259A_lock, flags); > + > outb(0xff, PIC_SLAVE_IMR); /* mask all of 8259A-2 */ > outb(probe_val, PIC_MASTER_IMR); > new_val = inb(PIC_MASTER_IMR); > if (new_val != probe_val) { > printk(KERN_INFO "Using NULL legacy PIC\n"); > legacy_pic = &null_legacy_pic; > - raw_spin_unlock_irqrestore(&i8259A_lock, flags); > - return; > } > > + raw_spin_unlock_irqrestore(&i8259A_lock, flags); > +} > + > +static void init_8259A(int auto_eoi) > +{ > + unsigned long flags; > + > + i8259A_auto_eoi = auto_eoi; > + > + raw_spin_lock_irqsave(&i8259A_lock, flags); > + > outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */ > > /* > @@ -388,6 +394,7 @@ struct legacy_pic null_legacy_pic = { > .mask_all = legacy_pic_noop, > .restore_mask = legacy_pic_noop, > .init = legacy_pic_int_noop, > + .probe = legacy_pic_noop, > .irq_pending = legacy_pic_irq_pending_noop, > .make_irq = legacy_pic_uint_noop, > }; > @@ -400,6 +407,7 @@ struct legacy_pic default_legacy_pic = { > .mask_all = mask_8259A, > .restore_mask = unmask_8259A, > .init = init_8259A, > + .probe = probe_8259A, > .irq_pending = i8259A_irq_pending, > .make_irq = make_8259A_irq, > }; > -- > 2.4.3 > > -- > 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/ >