Re: [PATCH v15 01/15] platform-msi: Add msi_remove_device_irq_domain() in platform_device_msi_free_irqs_all()

[Marc Zyngier <maz@kernel.org>]

On Tue, 11 Feb 2025 19:21:54 +0000,
Frank Li <Frank.Li@nxp.com> wrote:
> 
> The follow steps trigger kernel dump warning and
> platform_device_msi_init_and_alloc_irqs() return false.
> 
> 1: platform_device_msi_init_and_alloc_irqs();
> 2: platform_device_msi_free_irqs_all();
> 3: platform_device_msi_init_and_alloc_irqs();
> 
> [   76.713677] WARNING: CPU: 3 PID: 134 at kernel/irq/msi.c:1028 msi_create_device_irq_domain+0x1bc/0x22c
> [   76.723010] Modules linked in:
> [   76.726082] CPU: 3 UID: 0 PID: 134 Comm: kworker/3:1H Not tainted 6.13.0-rc1-00015-gd60b98003b43-dirty #57
> [   76.735741] Hardware name: NXP i.MX95 19X19 board (DT)
> [   76.740883] Workqueue: kpcitest pci_epf_test_cmd_handler
> [   76.746212] pstate: a0400009 (NzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   76.753172] pc : msi_create_device_irq_domain+0x1bc/0x22c
> [   76.758586] lr : msi_create_device_irq_domain+0x104/0x22c
> [   76.763988] sp : ffff800083f43be0
> [   76.767313] x29: ffff800083f43be0 x28: 0000000000000000 x27: ffff8000827a7000
> [   76.774466] x26: ffff00008085f400 x25: ffff00008000b180 x24: ffff000080fc6410
> [   76.781624] x23: ffff000085704cc0 x22: ffff8000811c8828 x21: ffff000085704cc0
> [   76.788774] x20: ffff000082814000 x19: 0000000000000000 x18: ffffffffffffffff
> [   76.795933] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> [   76.803083] x14: 0000000000000000 x13: 0000000f00000000 x12: 0000000000000000
> [   76.810233] x11: 0000000000000000 x10: 000000000000002d x9 : ffff800083f43ba0
> [   76.817383] x8 : 00000000ffffffff x7 : 0000000000000019 x6 : ffff0000857e443a
> [   76.824533] x5 : 0000000000000000 x4 : ffffffffffffffff x3 : ffff000085704ce8
> [   76.831683] x2 : ffff000080835640 x1 : 0000000000000213 x0 : ffff0000877189c0
> [   76.838840] Call trace:
> [   76.841287]  msi_create_device_irq_domain+0x1bc/0x22c (P)
> [   76.846701]  msi_create_device_irq_domain+0x104/0x22c (L)
> [   76.852118]  platform_device_msi_init_and_alloc_irqs+0x6c/0xb8
> 
> Do below two things in platform_device_msi_init_and_alloc_irqs().
> - msi_create_device_irq_domain()
> - msi_domain_alloc_irqs_range()
> 
> But only call msi_domain_free_irqs_all() in
> platform_device_msi_free_irqs_all(), which missed call
> msi_remove_device_irq_domain(). This cause above kernel dump when call
> platform_device_msi_init_and_alloc_irqs() again.

I don't think this commit message makes much sense, and doesn't
explain the essential problem, which is the lack of symmetry. I'd
suggest something like:

"platform_device_msi_init_and_alloc_irqs() performs two tasks:
allocating the MSI domain for a platform device, and allocate a number
of MSIs in that domain.

platform_device_msi_free_irqs_all() only frees the MSIs, and leaves
the MSI domain alive.

Given that platform_device_msi_init_and_alloc_irqs() is the sole tool
a platform device has to allocate platform MSIs, it would make sense
for platform_device_msi_free_irqs_all() to teardown the MSI domain at
the same time as the MSIs.

This also avoids warnings and unexpected behaviours when a driver
repeatedly allocates and frees MSIs."

With that:

Acked-by: Marc Zyngier <maz@kernel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.