netdev - [PATCH iwl-net 0/4] igb: fix igb_msix_other() handling for PREEMPT

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241204114229.21452-1-wander@redhat.com>
Date: Wed,  4 Dec 2024 08:42:23 -0300
From: Wander Lairson Costa <wander@...hat.com>
To: Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Clark Williams <clrkwllms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jeff Garzik <jgarzik@...hat.com>,
	Auke Kok <auke-jan.h.kok@...el.com>,
	intel-wired-lan@...ts.osuosl.org (moderated list:INTEL ETHERNET DRIVERS),
	netdev@...r.kernel.org (open list:NETWORKING DRIVERS),
	linux-kernel@...r.kernel.org (open list),
	linux-rt-devel@...ts.linux.dev (open list:Real-time Linux (PREEMPT_RT):Keyword:PREEMPT_RT)
Cc: Wander Lairson Costa <wander@...hat.com>
Subject: [PATCH iwl-net 0/4] igb: fix igb_msix_other() handling for PREEMPT_RT

This is the second attempt at fixing the behavior of igb_msix_other()
for PREEMPT_RT. The previous attempt [1] was reverted [2] following
concerns raised by Sebastian [3].

The initial approach proposed converting vfs_lock to a raw_spinlock,
a minor change intended to make it safe. However, it became evident
that igb_rcv_msg_from_vf() invokes kcalloc with GFP_ATOMIC,
which is unsafe in interrupt context on PREEMPT_RT systems.

To address this, the solution involves splitting igb_msg_task()
into two parts:

    * One part invoked from the IRQ context.
    * Another part called from the threaded interrupt handler.

To accommodate this, vfs_lock has been restructured into a double
lock: a spinlock_t and a raw_spinlock_t. In the revised design:

    * igb_disable_sriov() locks both spinlocks.
    * Each part of igb_msg_task() locks the appropriate spinlock for
    its execution context.

It is worth noting that the double lock mechanism is only active under
PREEMPT_RT. For non-PREEMPT_RT builds, the additional raw_spinlock_t
field is ommited.

If the extra raw_spinlock_t field can be tolerated under
!PREEMPT_RT (even though it remains unused), we can eliminate the
need for #ifdefs and simplify the code structure.

I will be on vacation from December 7th to Christmas and will address
review comments upon my return.

If possible, I kindly request the Intel team to perform smoke tests
on both stock and realtime kernels to catch any potential issues with
this patch series.

Cheers,
Wander

[1] https://lore.kernel.org/all/20240920185918.616302-2-wander@redhat.com/
[2] https://lore.kernel.org/all/20241104124050.22290-1-wander@redhat.com/
[3] https://lore.kernel.org/all/20241104110708.gFyxRFlC@linutronix.de/

Wander Lairson Costa (4):
  igb: narrow scope of vfs_lock in SR-IOV cleanup
  igb: introduce raw vfs_lock to igb_adapter
  igb: split igb_msg_task()
  igb: fix igb_msix_other() handling for PREEMPT_RT

 drivers/net/ethernet/intel/igb/igb.h      |   4 +
 drivers/net/ethernet/intel/igb/igb_main.c | 160 +++++++++++++++++++---
 2 files changed, 148 insertions(+), 16 deletions(-)

-- 
2.47.0