linux-kernel - Re: [PATCH 1/1] um: virt-pci: Switch to msi_create_parent_irq

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Message-ID: <20250627084943.nCYOI4Vp@linutronix.de>
Date: Fri, 27 Jun 2025 10:49:43 +0200
From: Nam Cao <namcao@...utronix.de>
To: Johannes Berg <johannes@...solutions.net>
Cc: Marc Zyngier <maz@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Richard Weinberger <richard@....at>,
	Anton Ivanov <anton.ivanov@...bridgegreys.com>,
	linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] um: virt-pci: Switch to
 msi_create_parent_irq_domain()

On Fri, Jun 27, 2025 at 10:24:38AM +0200, Johannes Berg wrote:
> On Thu, 2025-06-26 at 16:47 +0200, Nam Cao wrote:
> > Move away from the legacy MSI domain setup, switch to use
> > msi_create_parent_irq_domain().
> 
> I applied this on 6.16-rc1 (plus a handful of local patches), and got a
> lockdep warning and kernel crash with this change:

Thanks for testing! The later kernel crash should be fixed with:

diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
index e51a9357934da..557d93aea00a1 100644
--- a/arch/um/drivers/virt-pci.c
+++ b/arch/um/drivers/virt-pci.c
@@ -407,7 +407,6 @@ static const struct irq_domain_ops um_pci_inner_domain_ops = {
 
 #define UM_PCI_MSI_FLAGS_REQUIRED (MSI_FLAG_USE_DEF_DOM_OPS		| \
 				   MSI_FLAG_USE_DEF_CHIP_OPS		| \
-				   MSI_FLAG_PCI_MSI_MASK_PARENT		| \
 				   MSI_FLAG_NO_AFFINITY)
 #define UM_PCI_MSI_FLAGS_SUPPORTED (MSI_GENERIC_FLAGS_MASK		| \
 				    MSI_FLAG_PCI_MSIX)


I have no immediate idea about the lockdep warn, I don't see how the
MSI_FLAG_PCI_MSI_MASK_PARENT flag can be related to that. Probably there's
another problem, let me stare at it..

Nam