linux-kernel - Re: [PATCH v3 19/35] x86/io_apic: Cleanup trigger/polarity helpers

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Date:   Tue, 10 Nov 2020 08:59:17 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Qian Cai <cai@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Tom Murphy <murphyt7@....ie>
Cc:     kvm <kvm@...r.kernel.org>, iommu@...ts.linux-foundation.org,
        joro@...tes.org, Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-hyperv@...r.kernel.org, maz@...terjones.org,
        Dexuan Cui <decui@...rosoft.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [PATCH v3 19/35] x86/io_apic: Cleanup trigger/polarity helpers

On Tue, 2020-11-10 at 01:31 -0500, Qian Cai wrote:
> On Sat, 2020-10-24 at 22:35 +0100, David Woodhouse wrote:
> > From: Thomas Gleixner <tglx@...utronix.de>
> > 
> > 'trigger' and 'polarity' are used throughout the I/O-APIC code for handling
> > the trigger type (edge/level) and the active low/high configuration. While
> > there are defines for initializing these variables and struct members, they
> > are not used consequently and the meaning of 'trigger' and 'polarity' is
> > opaque and confusing at best.
> > 
> > Rename them to 'is_level' and 'active_low' and make them boolean in various
> > structs so it's entirely clear what the meaning is.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
> > ---
> >   arch/x86/include/asm/hw_irq.h       |   6 +-
> >   arch/x86/kernel/apic/io_apic.c      | 244 +++++++++++++---------------
> >   arch/x86/pci/intel_mid_pci.c        |   8 +-
> >   drivers/iommu/amd/iommu.c           |  10 +-
> >   drivers/iommu/intel/irq_remapping.c |   9 +-
> >   5 files changed, 130 insertions(+), 147 deletions(-)
> 
> Reverting the rest of patchset up to this commit on next-20201109 fixed an
> endless soft-lockups issue booting an AMD server below. I noticed that the
> failed boots always has this IOMMU IO_PAGE_FAULT before those soft-lockups:

Hm, attempting to reproduce this shows something else. Ever since
commit be62dbf554c5 ("iommu/amd: Convert AMD iommu driver to the dma-
iommu api") in 5.5 the following stops working for me:

$ qemu-system-x86_64 -serial mon:stdio -kernel bzImage  -machine q35,accel=kvm,kernel-irqchip=split -m 2G -device amd-iommu,intremap=off -append "console=ttyS0 apic=verbose debug" -display none

It hasn't got a hard drive but I can watch the SATA interrupts fail as
it probes the CD-ROM:

[    7.403327] ata3.00: qc timeout (cmd 0xa1)
[    7.405980] ata3.00: failed to IDENTIFY (I/O error, err_mask=0x4)

Adding 'iommu=off' to the kernel command line makes it work again, in
that it correctly panics at the lack of a root file system, quickly.



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