Re: [PATCH] hw/nvme: fix assertion failure on subregion removal when removing a nvme controller with a msix exclusive bar

Klaus Jensen <[email protected]> Tue, 28 Jul 2026 09:46:08 +0200

Newsgroups	gmane.comp.emulators.qemu.block,gmane.comp.emulators.qemu
Message-ID	<[email protected]>

On Jul 26 20:30, Daniel Paziyski wrote:
> When a controller is created with a MSI-X exclusive BAR, the bar0 memory region
> is not used at all, and so, the iomem region is not added as a subregion of it.
> However, when removing a NVMe controller, the iomem region is unconditionally
> removed as a subregion of bar0, causing an assertion failure. Remove the iomem
> memory region as a subregion of bar0 only if not using a MSI-X exclusive BAR.
> 
> QEMU options (requires a hotunplug-aware OS):
> 
>         -M q35 -device pcie-root-port,id=rp0 \
>         -device nvme,serial=ctrl0,id=ctrl0,bus=rp0,msix-exclusive-bar=on
> 
> In the QEMU monitor, or by causing an ejection from the OS:
> 
>         device_del ctrl0
> 
> Message in stderr:
> 
> qemu-system-x86_64: ../system/memory.c:2617: memory_region_del_subregion: Assertion `subregion->container == mr' failed.
> 
> Fixes: fa905f65c554 ("hw/nvme: add machine compatibility parameter to enable msix exclusive bar")
> Fixes: 9162f1012576 ("hw/nvme: fix msix_uninit with exclusive bar")
> Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4090
> Signed-off-by: Daniel Paziyski <[email protected]>
> ---
>  hw/nvme/ctrl.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
> index a67e159889..142fbe033e 100644
> --- a/hw/nvme/ctrl.c
> +++ b/hw/nvme/ctrl.c
> @@ -9710,10 +9710,9 @@ static void nvme_exit(PCIDevice *pci_dev)
>          msix_uninit_exclusive_bar(pci_dev);
>      } else {
>          msix_uninit(pci_dev, &n->bar0, &n->bar0);
> +        memory_region_del_subregion(&n->bar0, &n->iomem);
>      }
>  
> -    memory_region_del_subregion(&n->bar0, &n->iomem);
> -
>      migrate_del_blocker(&n->migration_blocker);
>  }
>  
> -- 
> 2.55.0
> 
> 

LGTM.

Reviewed-by: Klaus Jensen <[email protected]>

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