linux-kernel - Re: VMware PCI passthrough regression

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Date:	Thu, 14 Jan 2016 22:15:59 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jason Taylor <jason.taylor@...plivity.com>
cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	x86@...nel.org, Jiang Liu <jiang.liu@...ux.intel.com>
Subject: Re: VMware PCI passthrough regression

Jason,

On Thu, 14 Jan 2016, Jason Taylor wrote:

> I've run into a regression using PCI passthrough with the 4.4
> kernel.

Actually that is a 4.2 kernel according to the dmesg in the bug tracker.

> Attempting to passthrough an LSI card with ESXi version 6. Seeing
> timeouts and oops in the log and the disks do not show up.

The timeouts are probably related to missing irq delivery, so it might be
related to the big overhaul of the x86 irq subsystem.

The oops is a genuine driver bug probably unearthed by the irq issue. That
should be reported seperately to the megasas folks.

> I performed a bisect which tracked down the issue to the commit below.
> 
> More details are available in a bug report I filed with Ubuntu:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1528849
>
> commit 52f518a3a7c2f80551a38d38be28bc9f335e713c
> x86/MSI: Use hierarchical irqdomains to manage MSI interrupts

I have no idea how that breaks the vmware passthrough. Can you please verify

 - whether that kernel works on the real hardware with that LSI card

 - whether that kernel works in a KVM guest with that card passed through

If one of those things break, we can certainly help to analyse that. If not,
then you need to talk to vmware.

Thanks,

	tglx