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From: "Roger Pau Monné" <roger.pau@citrix.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Jason Andryuk <jandryuk@gmail.com>, <josef@oderland.se>,
	<boris.ostrovsky@oracle.com>, <helgaas@kernel.org>,
	<jgross@suse.com>, <linux-pci@vger.kernel.org>, <maz@kernel.org>,
	<tglx@linutronix.de>, <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH] PCI/MSI: Fix masking MSI/MSI-X on Xen PV
Date: Mon, 25 Oct 2021 13:43:55 +0200	[thread overview]
Message-ID: <YXaYe/RF6NWFKxGj@MacBook-Air-de-Roger.local> (raw)
In-Reply-To: <eb38c1d2707d03bf675d7b15f014cbe741de0998.camel@infradead.org>

On Mon, Oct 25, 2021 at 08:44:52AM +0100, David Woodhouse wrote:
> On Sun, 2021-10-24 at 21:25 -0400, Jason Andryuk wrote:
> > commit fcacdfbef5a1 ("PCI/MSI: Provide a new set of mask and unmask
> > functions") introduce functions pci_msi_update_mask() and
> > pci_msix_write_vector_ctrl() that is missing checks for
> > pci_msi_ignore_mask that exists in commit 446a98b19fd6 ("PCI/MSI: Use
> > new mask/unmask functions").  The checks are in place at the high level
> > __pci_msi_mask_desc()/__pci_msi_unmask_desc(), but some functions call
> > directly to the helpers.
> > 
> > Push the pci_msi_ignore_mask check down to the functions that make
> > the actual writes.  This keeps the logic local to the writes that need
> > to be bypassed.
> > 
> > With Xen PV, the hypervisor is responsible for masking and unmasking the
> > interrupts, which pci_msi_ignore_mask is used to indicate.
> 
> This isn't just for Xen PV; Xen HVM guests let Xen unmask the MSI for
> them too.

It's kind of optional for HVM guests, as it depends on
XENFEAT_hvm_pirqs, which sadly gets unconditionally set for HVM
guests, thus dropping any benefits from having hardware assisted APIC
virtualization or posted interrupts support.

AFAICT pci_msi_ignore_mask is not (correctly) set for HVM guest when
MSI interrupts are routed over event channels.

Regards, Roger.


  reply	other threads:[~2021-10-25 11:44 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-18  6:22 [PATCH] PCI/MSI: Re-add checks for skip masking MSI-X on Xen PV Josef Johansson
2021-10-19 19:57 ` Bjorn Helgaas
2021-10-19 20:15   ` Josef Johansson
2021-10-19 20:29     ` Bjorn Helgaas
2021-10-19 21:48       ` [PATCH v2] " Josef Johansson
2021-10-20 12:51         ` Marc Zyngier
2021-10-20 14:03           ` Jason Andryuk
2021-10-21  8:25             ` Josef Johansson
2021-10-24 18:55               ` Josef Johansson
2021-10-25  1:25                 ` [PATCH] PCI/MSI: Fix masking MSI/MSI-X " Jason Andryuk
2021-10-25  7:44                   ` David Woodhouse
2021-10-25 11:43                     ` Roger Pau Monné [this message]
2021-10-25 11:53                       ` David Woodhouse
2021-10-25 12:58                         ` Roger Pau Monné
2021-10-25 13:02                           ` David Woodhouse
2021-10-25 14:12                             ` Roger Pau Monné
2021-10-25 12:31                     ` Jason Andryuk
2021-10-25 12:27                   ` Jason Andryuk
2021-10-25 16:46                     ` Josef Johansson
2021-10-26 21:17                       ` Josef Johansson
2021-10-27  8:45                   ` Thomas Gleixner
2021-10-27  9:50                     ` [PATCH] PCI/MSI: Move non-mask check back into low level accessors Thomas Gleixner
2021-10-27  9:54                       ` Josef Johansson
2021-10-27 12:01                         ` Josef Johansson
2021-10-27 15:29                           ` Josef Johansson
2021-11-03 23:26                             ` Thomas Gleixner
2021-11-03 23:27                               ` [PATCH v2] " Thomas Gleixner
2021-11-09 14:53                                 ` Thomas Gleixner
2021-11-10 13:31                                   ` Josef Johansson
2021-11-10 16:05                                     ` Josef Johansson
2021-11-03 23:45                             ` [PATCH] " Thomas Gleixner
2021-11-04  9:00                               ` Josef Johansson
2021-11-04 17:12                               ` Peter Zijlstra
2021-11-04 17:31                               ` Vincent Guittot
2021-11-10 20:30                               ` Josef Johansson
2021-11-10 23:13                                 ` Josef Johansson
2021-10-27  9:57                       ` David Woodhouse
2021-10-25  1:25                 ` [PATCH v2] PCI/MSI: Re-add checks for skip masking MSI-X on Xen PV Jason Andryuk
2021-10-25 19:21                   ` Josef Johansson
2021-10-27  6:24                     ` David Woodhouse
2021-10-27  8:13                       ` Josef Johansson
2021-10-27  8:26                         ` David Woodhouse

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