linux-kernel - Re: [PATCH 0/2] dm mpath: Interface for explicit probing of active paths

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Message-ID: <5911e91974db637d4a3395e60244c2c52b27b4b4.camel@suse.com>
Date: Thu, 15 May 2025 17:00:41 +0200
From: Martin Wilck <mwilck@...e.com>
To: Benjamin Marzinski <bmarzins@...hat.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Christoph Hellwig
 <hch@...radead.org>,  Kevin Wolf <kwolf@...hat.com>,
 dm-devel@...ts.linux.dev, Hanna Czenczek <hreitz@...hat.com>, Mikulas
 Patocka <mpatocka@...hat.com>, snitzer@...nel.org, "Kernel Mailing List,
 Linux"	 <linux-kernel@...r.kernel.org>, Hannes Reinecke <hare@...e.com>
Subject: Re: [PATCH 0/2] dm mpath: Interface for explicit probing of active
 paths

On Thu, 2025-05-15 at 10:29 -0400, Benjamin Marzinski wrote:
> On Thu, May 15, 2025 at 12:34:13PM +0200, Martin Wilck wrote:
> > 
> > However, I suppose that depends on the permissions with which the
> > qemu
> > process is started, no? Wouldn't qemu need CAP_SYS_RAWIO for PCI
> > passthrough as well? 
> > 
> > I admit that I'm confused by the many indirections in qemu's scsi-
> > block
> > code flow. AFAICS qemu forwards everything except PRIN/PROUT to the
> > kernel block device in "scsi-block" mode. Correct me if I'm wrong.
> > 
> > Anwyway, let's not forget that we're talking about the kernel here.
> > While qemu is the main target application for this feature is
> > created,
> > any application can use it, and it may or may not run with
> > CAP_SYS_RAWIO.
> 
> Maybe I'm missing your issue, but QEMU is just using DM's existing
> ioctl
> forwarding code, which was already designed for general use, and I
> don't
> see any capability issues with this patchset itself.

I didn't mean it this way. I was rather musing about the question
whether doing SG_IO on multipath devices by forwarding them to the
current path makes sense.

Sorry for the confusing post.

Regards
Martin