Re: [PATCH v8 11/14] PCI/RCEC: Add RCiEP's linked RCEC to AER/ERR

From: Bjorn Helgaas
Date: Fri Oct 09 2020 - 17:30:15 EST

On Fri, Oct 09, 2020 at 12:57:45PM -0500, Bjorn Helgaas wrote:
> On Fri, Oct 02, 2020 at 11:47:32AM -0700, Sean V Kelley wrote:
> > From: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
> >
> > When attempting error recovery for an RCiEP associated with an RCEC device,
> > there needs to be a way to update the Root Error Status, the Uncorrectable
> > Error Status and the Uncorrectable Error Severity of the parent RCEC.
> > In some non-native cases in which there is no OS visible device
> > associated with the RCiEP, there is nothing to act upon as the firmware
> > is acting before the OS. So add handling for the linked 'rcec' in AER/ERR
> > while taking into account non-native cases.
> >
> > Co-developed-by: Sean V Kelley <sean.v.kelley@xxxxxxxxx>
> > Signed-off-by: Sean V Kelley <sean.v.kelley@xxxxxxxxx>
> > Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> > ---
> > drivers/pci/pcie/aer.c | 9 +++++----
> > drivers/pci/pcie/err.c | 39 ++++++++++++++++++++++++++++-----------
> > 2 files changed, 33 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index 65dff5f3457a..dccdba60b5d9 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -1358,17 +1358,18 @@ static int aer_probe(struct pcie_device *dev)
> > static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
> > {
> > int aer = dev->aer_cap;
> > + int rc = 0;
> > u32 reg32;
> > - int rc;
> > -
> >
> > /* Disable Root's interrupt in response to error messages */
> > pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
> > reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
> > pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
> >
> > - rc = pci_bus_error_reset(dev);
> > - pci_info(dev, "Root Port link has been reset\n");
> > + if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC) {
> > + rc = pci_bus_error_reset(dev);
> > + pci_info(dev, "Root Port link has been reset\n");
> > + }
> >
> > /* Clear Root Error Status */
> > pci_read_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, &reg32);
> > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> > index 38abd7984996..956ad4c86d53 100644
> > --- a/drivers/pci/pcie/err.c
> > +++ b/drivers/pci/pcie/err.c
> > @@ -149,7 +149,8 @@ static int report_resume(struct pci_dev *dev, void *data)
> > /**
> > * pci_walk_bridge - walk bridges potentially AER affected
> > * @bridge bridge which may be an RCEC with associated RCiEPs,
> > - * an RCiEP associated with an RCEC, or a Port.
> > + * or a Port.
> > + * @dev an RCiEP lacking an associated RCEC.
> > * @cb callback to be called for each device found
> > * @userdata arbitrary pointer to be passed to callback.
> > *
> > @@ -160,13 +161,20 @@ static int report_resume(struct pci_dev *dev, void *data)
> > * If the device provided has no subordinate bus, call the provided
> > * callback on the device itself.
> > */
> > -static void pci_walk_bridge(struct pci_dev *bridge, int (*cb)(struct pci_dev *, void *),
> > +static void pci_walk_bridge(struct pci_dev *bridge, struct pci_dev *dev,
> > + int (*cb)(struct pci_dev *, void *),
> > void *userdata)
> > {
> > - if (bridge->subordinate)
> > + /*
> > + * In a non-native case where there is no OS-visible reporting
> > + * device the bridge will be NULL, i.e., no RCEC, no PORT.
> > + */
> > + if (bridge && bridge->subordinate)
> > pci_walk_bus(bridge->subordinate, cb, userdata);
> > - else
> > + else if (bridge)
> > cb(bridge, userdata);
> > + else
> > + cb(dev, userdata);
> > }
> >
> > static pci_ers_result_t flr_on_rciep(struct pci_dev *dev)
> > @@ -196,16 +204,25 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> > type = pci_pcie_type(dev);
> > if (type == PCI_EXP_TYPE_ROOT_PORT ||
> > type == PCI_EXP_TYPE_DOWNSTREAM ||
> > - type == PCI_EXP_TYPE_RC_EC ||
> > - type == PCI_EXP_TYPE_RC_END)
> > + type == PCI_EXP_TYPE_RC_EC)
> > bridge = dev;
> > + else if (type == PCI_EXP_TYPE_RC_END)
> > + bridge = dev->rcec;
> > else
> > bridge = pci_upstream_bridge(dev);
> >
> > pci_dbg(dev, "broadcast error_detected message\n");
> > if (state == pci_channel_io_frozen) {
> > - pci_walk_bridge(bridge, report_frozen_detected, &status);
> > + pci_walk_bridge(bridge, dev, report_frozen_detected, &status);
> > if (type == PCI_EXP_TYPE_RC_END) {
> > + /*
> > + * The callback only clears the Root Error Status
> > + * of the RCEC (see aer.c). Only perform this for the
> > + * native case, i.e., an RCEC is present.
> > + */
> > + if (bridge)
> > + reset_subordinate_devices(bridge);
>
> Help me understand this. There are lots of callbacks in this picture,
> but I guess this "callback only clears Root Error Status" must refer
> to aer_root_reset(), i.e., the reset_subordinate_devices pointer?
>
> Of course, the caller of pcie_do_recovery() supplied that pointer.
> And we can infer that it must be aer_root_reset(), not
> dpc_reset_link(), because RCECs and RCiEPs are not allowed to
> implement DPC.
>
> I wish we didn't have either this assumption about what
> reset_subordinate_devices points to, or the assumption about what
> aer_root_reset() does. They both seem a little bit tenuous.
>
> We already made aer_root_reset() smart enough to check for RCECs. Can
> we put the FLR there, too? Then we wouldn't have this weird situation
> where reset_subordinate_devices() does a reset and clears error
> status, EXCEPT for this case where it only clears error status and we
> do the reset here?

Just as an example to make this concrete. Doesn't even compile.


diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index d6927e6535e5..e389db7cbba6 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -1372,28 +1372,45 @@ static int aer_probe(struct pcie_device *dev)
*/
static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
{
- int aer = dev->aer_cap;
+ int type = pci_pcie_type(dev);
+ struct pci_dev *root;
+ int aer = 0;
int rc = 0;
u32 reg32;

- /* Disable Root's interrupt in response to error messages */
- pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
- reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
- pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
+ if (type == PCI_EXP_TYPE_RC_END)
+ root = dev->rcec;
+ else
+ root = dev;
+
+ if (root)
+ aer = root->aer_cap;

- if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC) {
+ if (aer) {
+ /* Disable Root's interrupt in response to error messages */
+ pci_read_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, &reg32);
+ reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
+ pci_write_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, reg32);
+ }
+
+ if (type == PCI_EXP_TYPE_RC_EC || type == PCI_EXP_TYPE_RC_END) {
+ rc = flr_on_rciep(dev);
+ pci_info(dev, "has been reset (%d)\n", rc);
+ } else {
rc = pci_bus_error_reset(dev);
- pci_info(dev, "Root Port link has been reset\n");
+ pci_info(dev, "Root Port link has been reset (%d)\n", rc);
}

- /* Clear Root Error Status */
- pci_read_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, &reg32);
- pci_write_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, reg32);
+ if (aer) {
+ /* Clear Root Error Status */
+ pci_read_config_dword(root, aer + PCI_ERR_ROOT_STATUS, &reg32);
+ pci_write_config_dword(root, aer + PCI_ERR_ROOT_STATUS, reg32);

- /* Enable Root Port's interrupt in response to error messages */
- pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
- reg32 |= ROOT_PORT_INTR_ON_MESG_MASK;
- pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
+ /* Enable Root Port's interrupt in response to error messages */
+ pci_read_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, &reg32);
+ reg32 |= ROOT_PORT_INTR_ON_MESG_MASK;
+ pci_write_config_dword(root, aer + PCI_ERR_ROOT_COMMAND, reg32);
+ }

return rc ? PCI_ERS_RESULT_DISCONNECT : PCI_ERS_RESULT_RECOVERED;
}
diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index 79ae1356141d..08976034a89c 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -203,36 +203,19 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
*/
if (type == PCI_EXP_TYPE_ROOT_PORT ||
type == PCI_EXP_TYPE_DOWNSTREAM ||
- type == PCI_EXP_TYPE_RC_EC)
+ type == PCI_EXP_TYPE_RC_EC ||
+ type == PCI_EXP_TYPE_RC_END)
bridge = dev;
- else if (type == PCI_EXP_TYPE_RC_END)
- bridge = dev->rcec;
else
bridge = pci_upstream_bridge(dev);

pci_dbg(bridge, "broadcast error_detected message\n");
if (state == pci_channel_io_frozen) {
pci_walk_bridge(bridge, dev, report_frozen_detected, &status);
- if (type == PCI_EXP_TYPE_RC_END) {
- /*
- * The callback only clears the Root Error Status
- * of the RCEC (see aer.c). Only perform this for the
- * native case, i.e., an RCEC is present.
- */
- if (bridge)
- reset_subordinates(bridge);
-
- status = flr_on_rciep(dev);
- if (status != PCI_ERS_RESULT_RECOVERED) {
- pci_warn(dev, "Function Level Reset failed\n");
- goto failed;
- }
- } else {
- status = reset_subordinates(bridge);
- if (status != PCI_ERS_RESULT_RECOVERED) {
- pci_warn(dev, "subordinate device reset failed\n");
- goto failed;
- }
+ status = reset_subordinates(bridge);
+ if (status != PCI_ERS_RESULT_RECOVERED) {
+ pci_warn(bridge, "subordinate device reset failed\n");
+ goto failed;
}
} else {
pci_walk_bridge(bridge, dev, report_normal_detected, &status);