linux-kernel - Re: [PATCH 2/3] PCI/ERR: Clear fatal status in pcie_do

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Date:   Mon, 26 Sep 2022 13:09:06 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Zhuo Chen <chenzhuo.1@...edance.com>
Cc:     allenbh@...il.com, dave.jiang@...el.com,
        linux-scsi@...r.kernel.org, martin.petersen@...cle.com,
        linux-pci@...r.kernel.org, jejb@...ux.ibm.com, jdmason@...zu.us,
        james.smart@...adcom.com, fancer.lancer@...il.com,
        linux-kernel@...r.kernel.org, ntb@...ts.linux.dev,
        oohall@...il.com, bhelgaas@...gle.com, dick.kennedy@...adcom.com,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 2/3] PCI/ERR: Clear fatal status in pcie_do_recovery()

On Mon, Sep 26, 2022 at 10:01:55PM +0800, Zhuo Chen wrote:
> On 9/23/22 5:08 AM, Bjorn Helgaas wrote:
> > On Fri, Sep 02, 2022 at 02:16:33AM +0800, Zhuo Chen wrote:
> > > When state is pci_channel_io_frozen in pcie_do_recovery(),
> > > the severity is fatal and fatal status should be cleared.
> > > So we add pci_aer_clear_fatal_status().
> > 
> > Seems sensible to me.  Did you find this by code inspection or by
> > debugging a problem?  If the latter, it would be nice to mention the
> > symptoms of the problem in the commit log.
> 
> I found this by code inspection so I may not enumerate what kind of problems
> this code will cause.
> > 
> > > Since pcie_aer_is_native() in pci_aer_clear_fatal_status()
> > > and pci_aer_clear_nonfatal_status() contains the function of
> > > 'if (host->native_aer || pcie_ports_native)', so we move them
> > > out of it.
> > 
> > Wrap commit log to fill 75 columns.
> > 
> > > Signed-off-by: Zhuo Chen <chenzhuo.1@...edance.com>
> > > ---
> > >   drivers/pci/pcie/err.c | 8 ++++++--
> > >   1 file changed, 6 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> > > index 0c5a143025af..e0a8ade4c3fe 100644
> > > --- a/drivers/pci/pcie/err.c
> > > +++ b/drivers/pci/pcie/err.c
> > > @@ -243,10 +243,14 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> > >   	 * it is responsible for clearing this status.  In that case, the
> > >   	 * signaling device may not even be visible to the OS.
> > >   	 */
> > > -	if (host->native_aer || pcie_ports_native) {
> > > +	if (host->native_aer || pcie_ports_native)
> > >   		pcie_clear_device_status(dev);
> > 
> > pcie_clear_device_status() doesn't check for pcie_aer_is_native()
> > internally, but after 068c29a248b6 ("PCI/ERR: Clear PCIe Device Status
> > errors only if OS owns AER") and aa344bc8b727 ("PCI/ERR: Clear AER
> > status only when we control AER"), both callers check before calling
> > it.
> > 
> > I think we should move the check inside pcie_clear_device_status().
> > That could be a separate preliminary patch.
> > 
> > There are a couple other places (aer_root_reset() and
> > get_port_device_capability()) that do the same check and could be
> > changed to use pcie_aer_is_native() instead.  That could be another
> > preliminary patch.
> > 
> Good suggestion. But I have only one doubt. In aer_root_reset(), if we use
> "if (pcie_aer_is_native(dev) && aer)", when dev->aer_cap
> is NULL and root->aer_cap is not NULL, pcie_aer_is_native() will return
> false. It's different from just using "(host->native_aer ||
> pcie_ports_native)".
> Or if we can use "if (pcie_aer_is_native(root))", at this time a NULL
> pointer check should be added in pcie_aer_is_native() because root may be
> NULL.

Good point.  In aer_root_reset(), we're updating Root Port registers,
so I think they should look like:

  if (pcie_aer_is_native(root) && aer) {
    ...
  }

Does that seem safe and equivalent to you?

Bjorn