From: Thomas Gleixner <tglx@linutronix.de>
To: Megha Dey <megha.dey@intel.com>
Cc: bhelgaas@google.com, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org, marc.zyngier@arm.com,
ashok.raj@intel.com, jacob.jun.pan@linux.intel.com,
megha.dey@linux.intel.com
Subject: Re: [RFC V1 RESEND 5/6] PCI/MSI: Free MSI-X resources by group
Date: Sun, 11 Aug 2019 09:18:59 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1908110912470.7324@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1565118597.2401.116.camel@intel.com>
[-- Attachment #1: Type: text/plain, Size: 3233 bytes --]
On Tue, 6 Aug 2019, Megha Dey wrote:
> On Sat, 2019-06-29 at 10:08 +0200, Thomas Gleixner wrote:
> > Megha,
> >
> > On Fri, 21 Jun 2019, Megha Dey wrote:
> > >
> > > +static int free_msi_irqs_grp(struct pci_dev *dev, int group_id)
> > > +{
> > >
> > > +
> > > + for_each_pci_msi_entry(entry, dev) {
> > > + if (entry->group_id == group_id && entry->irq)
> > > + for (i = 0; i < entry->nvec_used; i++)
> > > + BUG_ON(irq_has_action(entry->irq +
> > > i));
> > BUG_ON is wrong here. This can and must be handled gracefully.
> >
>
> Hmm, I reused this code from the 'free_msi_irqs' function. I am not
> sure why it is wrong to use BUG_ON here but ok to use it there, please
> let me know.
We are not adding BUG_ON() anymore except for situations where there is
absolutely no way out. Just because there is still older code having
BUG_ON() does not make it any better. Copying it surely is no
justification.
If there is really no way out, then you need to explain it.
> > > +static void pci_msix_shutdown_grp(struct pci_dev *dev, int
> > > group_id)
> > > +{
> > > + struct msi_desc *entry;
> > > + int grp_present = 0;
> > > +
> > > + if (pci_dev_is_disconnected(dev)) {
> > > + dev->msix_enabled = 0;
> > Huch? What's that? I can't figure out why this is needed and of
> > course it
> > completely lacks a comment explaining this.
> >
>
> Again, I have reused this code from the pci_msix_shutdown() function.
> So for the group case, this is not required?
Copy and paste is not an argument, really. Can this happen here? If so,
then please add a comment.
> > >
> > > + return;
> > > + }
> > > +
> > > + /* Return the device with MSI-X masked as initial states
> > > */
> > > + for_each_pci_msi_entry(entry, dev) {
> > > + if (entry->group_id == group_id) {
> > > + /* Keep cached states to be restored */
> > > + __pci_msix_desc_mask_irq(entry, 1);
> > > + grp_present = 1;
> > > + }
> > > + }
> > > +
> > > + if (!grp_present) {
> > > + pci_err(dev, "Group to be disabled not
> > > present\n");
> > > + return;
> > So you print an error and silently return
> >
>
> This is a void function, hence no error value can be returned. What do
> you think is the right thing to do if someone wants to delete a group
> which is not present?
Well, you made it a void function.
> > >
> > > + }
> > > +}
> > > +
> > > +int pci_disable_msix_grp(struct pci_dev *dev, int group_id)
> > > +{
> > > + int num_vecs;
> > > +
> > > + if (!pci_msi_enable || !dev)
> > > + return -EINVAL;
> > > +
> > > + pci_msix_shutdown_grp(dev, group_id);
> > > + num_vecs = free_msi_irqs_grp(dev, group_id);
> > just to call in another function which has to do the same group_id
> > lookup
> > muck again.
>
> Even with the new proposal, we are to have 2 sets of functions: one to
> delete all the msic_desc entries associated with the device, and the
> other to delete those only belonging a 'user specified' group. So we do
> need to pass a group_id to these functions right? Yes, internally the
> deletion would be straightforward with the new approach.
That does not matter. If pci_msix_shutdown_grp() does not find a group, why
proceeding instead of having a proper error return and telling the caller?
Thanks,
tglx
next prev parent reply other threads:[~2019-08-11 7:19 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-22 0:19 [RFC V1 RESEND 0/6] Introduce dynamic allocation/freeing of MSI-X vectors Megha Dey
2019-06-22 0:19 ` [RFC V1 RESEND 1/6] PCI/MSI: New structures/macros for dynamic MSI-X allocation Megha Dey
2019-06-22 0:19 ` [RFC V1 RESEND 2/6] PCI/MSI: Dynamic allocation of MSI-X vectors by group Megha Dey
2019-06-29 7:59 ` Thomas Gleixner
2019-08-06 19:05 ` Megha Dey
2019-08-07 13:56 ` Thomas Gleixner
2019-08-07 14:18 ` Marc Zyngier
2019-08-11 7:20 ` Thomas Gleixner
2019-08-12 17:54 ` Megha Dey
2019-08-12 17:48 ` Megha Dey
2019-08-12 17:47 ` Megha Dey
2021-01-07 22:30 ` Jacob Keller
2019-06-22 0:19 ` [RFC V1 RESEND 3/6] x86: Introduce the dynamic teardown function Megha Dey
2019-06-29 8:01 ` Thomas Gleixner
2019-08-06 19:06 ` Megha Dey
2019-06-22 0:19 ` [RFC V1 RESEND 4/6] PCI/MSI: Introduce new structure to manage MSI-x entries Megha Dey
2019-06-22 0:19 ` [RFC V1 RESEND 5/6] PCI/MSI: Free MSI-X resources by group Megha Dey
2019-06-29 8:08 ` Thomas Gleixner
2019-08-06 19:09 ` Megha Dey
2019-08-11 7:18 ` Thomas Gleixner [this message]
2019-08-12 18:13 ` Megha Dey
2019-06-22 0:19 ` [RFC V1 RESEND 6/6] Documentation: PCI/MSI: Document dynamic MSI-X infrastructure Megha Dey
2019-08-02 0:24 ` [RFC V1 RESEND 0/6] Introduce dynamic allocation/freeing of MSI-X vectors Bjorn Helgaas
2019-08-06 19:12 ` Megha Dey
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