** Description changed:
+ SRU Justification:
+
+ [ Impact ]
+
+ * For non-VFs, function zpci_bus_is_isolated_vf() should return false,
+ because they aren't VFs.
+ While zpci_iov_find_parent_pf() specifically checks if a function is a VF,
+ it then simply returns that there is no parent.
+
+ * The simplistic check for a parent then leads to these functions being
+ confused with isolated VFs, and isolating them on their own domain even
+ if sibling PFs should share the domain.
+
+ [ Fix ]
+
+ * This is fixed by explicitly checking if a function is not a VF.
+ (Notice that at this point the case where RIDs are ignored is already
+ handled - and in this case all PCI functions get isolated by being
+ properly detected in zpci_bus_is_multifunction_root().)
+
+ * 8691abd3afaa "s390/pci: Fix zpci_bus_is_isolated_vf() for non-VFs"
+
+ [ Test Plan ]
+
+ * Setup Ubuntu Server (24.04/24.10) for s390x on an IBM z17
+ or LinuxONE 5 LPAR.
+
+ * Have at least two PCIe adapters that support PF/VF (like RoCE Express)
+ available in that LPAR.
+
+ * Attach multiple PFs of a PF access mode device (notice that this is only
+ possible with z17 and L1-5 hardware), such as the two PFs of a NETD
+ to the same LPAR.
+
+ * Observe that they are put into separate PCI domains
+ instead of sharing the same domain as expected by drivers.
+
+ * Due to lack of hardware, the verification will be conducted by IBM.
+
+ * The fix was discussed upstream and flagged a stable kernel update.
+
+ [ Where problems could occur ]
+
+ * The modification is limited to one additional if statement
+ across two lines) in function zpci_bus_is_isolated_vf()
+ in file arch/s390/pci/pci_bus.c.
+
+ * Hence the modification will be limited to the s390x-specific parts of
+ the PCI code in the kernel (sometimes refers to as zPCI),
+ and will NOT impact any other architecture!
+
+ * If add. if-statement is not correct and a wrong bool is returned,
+ function zpci_bus_is_isolated_vf() might report and incorrect zpci_bus
+ status. Either isolated when it's not or not-isolated when it really is.
+
+ * And since the new if statement got inserted before the already existing
+ 'if (!pdev)', the latter code in function zpci_bus_is_isolated_vf()
+ might be accidentally skipped.
+
+ * All this might lead to a similar confusion of the functions in regard to
+ isolated VFs status and whether isolating them on their own domain even
+ or not, hence proper testing is needed.
+
+ [ Other Info ]
+
+ * Since the commit got upstream accepted with v6.15-rc1,
+ 'Questing' is not affected.
+
+ * Plucky got fixed with
+ https://bugs.launchpad.net/bugs/2108854
+ (cherry-picked as
https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/plucky/commit/?id=58412b2aa12aa43c90d5414e22898a041ec05e8a)
+
+ * Hence the only remaining affected releases, that contain the offending
+ commit ("s390/pci: Fix handling of isolated VFs"), are oracular and noble.
+
+ * Since this issue does not happen (thus cannot be recreated nor tested)
+ on the IBM Z hardware we have in Canonical, the verification(s) will be
+ done by IBM on most recent hardware.
+ __________
+
s390/pci: Fix zpci_bus_is_isolated_vf() for non-VFs
- Commit:
+ Commit:
8691abd3afaadd816a298503ec1a759df1305d2e
-------------------------
- For non-VFs, zpci_bus_is_isolated_vf() should return false
because they
- aren't VFs. While zpci_iov_find_parent_pf() specifically checks
if
- a function is a VF, it then simply returns that there is no
parent. The
- simplistic check for a parent then leads to these functions
being
- confused with isolated VFs and isolating them on their own
domain even
- if sibling PFs should share the domain.
+ For non-VFs, zpci_bus_is_isolated_vf() should return false
because they
+ aren't VFs. While zpci_iov_find_parent_pf() specifically checks
if
+ a function is a VF, it then simply returns that there is no
parent. The
+ simplistic check for a parent then leads to these functions
being
+ confused with isolated VFs and isolating them on their own
domain even
+ if sibling PFs should share the domain.
- Fix this by explicitly checking if a function is not a VF. Note
also
- that at this point the case where RIDs are ignored is already
handled
- and in this case all PCI functions get isolated by being
detected in
- zpci_bus_is_multifunction_root().
+ Fix this by explicitly checking if a function is not a VF. Note
also
+ that at this point the case where RIDs are ignored is already
handled
+ and in this case all PCI functions get isolated by being
detected in
+ zpci_bus_is_multifunction_root().
- Cc: [email protected]
- Fixes: 2844ddbd540f ("s390/pci: Fix handling of isolated VFs")
- Signed-off-by: Niklas Schnelle <[email protected]>
- Reviewed-by: Halil Pasic <[email protected]>
- Signed-off-by: Vasily Gorbik <[email protected]>
+ Cc: [email protected]
+ Fixes: 2844ddbd540f ("s390/pci: Fix handling of isolated VFs")
+ Signed-off-by: Niklas Schnelle <[email protected]>
+ Reviewed-by: Halil Pasic <[email protected]>
+ Signed-off-by: Vasily Gorbik <[email protected]>
** Changed in: ubuntu-z-systems
Status: Triaged => Confirmed
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https://bugs.launchpad.net/bugs/2111599
Title:
[UBUNTU 24.04] s390/pci: Fix zpci_bus_is_isolated_vf() for non-VF
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