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A urgent fix for the XEN related PCI/MSI changes:

Browse source 
XEN used a global variable to disable the masking of MSI interrupts as
   XEN handles that on the hypervisor side. This turned out to be a problem
   with VMD as the PCI devices behind a VMD bridge are not always handled
   by the hypervisor and then require masking by guest.
 
   To solve this the global variable was replaced by a interrupt domain
   specific flag, which is set by the generic XEN PCI/MSI domain, but not by
   VMD or any other domain in the system.
 
   So far, so good. But the implementation (and the reviewer) missed the
   fact, that accessing the domain flag cannot be done directly because
   there are at least two situations, where this fails. Legacy architectures
   are not providing interrupt domains at all. The new MSI parent domains do
   not require to have a domain info pointer. Both cases result in a
   unconditional NULL pointer derefence.
 
   The PCI/MSI code already has a function to query the MSI domain specific
   flag in a safe way, which handles all possible cases of PCI/MSI backends.
 
   So the fix it simply to replace the open coded checks by invoking the
   safe helper to query the flag.
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Merge tag 'irq-urgent-2025-03-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull MSI irq fix from Thomas Gleixner:
 "An urgent fix for the XEN related PCI/MSI changes:

  XEN used a global variable to disable the masking of MSI interrupts as
  XEN handles that on the hypervisor side. This turned out to be a
  problem with VMD as the PCI devices behind a VMD bridge are not always
  handled by the hypervisor and then require masking by guest.

  To solve this the global variable was replaced by a interrupt domain
  specific flag, which is set by the generic XEN PCI/MSI domain, but not
  by VMD or any other domain in the system.

  So far, so good. But the implementation (and the reviewer) missed the
  fact, that accessing the domain flag cannot be done directly because
  there are at least two situations, where this fails.

  Legacy architectures are not providing interrupt domains at all. The
  new MSI parent domains do not require to have a domain info pointer.
  Both cases result in a unconditional NULL pointer derefence.

  The PCI/MSI code already has a function to query the MSI domain
  specific flag in a safe way, which handles all possible cases of
  PCI/MSI backends.

  So the fix it simply to replace the open coded checks by invoking the
  safe helper to query the flag"

* tag 'irq-urgent-2025-03-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  PCI/MSI: Handle the NOMASK flag correctly for all PCI/MSI backends
This commit is contained in:
Linus Torvalds 2025-03-26 13:20:22 -07:00
commit 87dc996d56
1 changed files with 6 additions and 12 deletions
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