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Message-ID: <57f3f757aaceccf866172faaf48ab62916f24d8b.camel@infradead.org>
Subject: Re: [patch V3 16/22] genirq/msi: Provide new domain id based
 interfaces for freeing interrupts
From:   David Woodhouse <dwmw2@infradead.org>
To:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Juergen Gross <jgross@suse.com>,
        xen-devel <xen-devel@lists.xen.org>
Cc:     x86@kernel.org, Joerg Roedel <joro@8bytes.org>,
        Will Deacon <will@kernel.org>, linux-pci@vger.kernel.org,
        Bjorn Helgaas <bhelgaas@google.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jason Gunthorpe <jgg@mellanox.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Kevin Tian <kevin.tian@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        Ashok Raj <ashok.raj@intel.com>, Jon Mason <jdmason@kudzu.us>,
        Allen Hubbe <allenbh@gmail.com>
Date:   Mon, 16 Jan 2023 19:28:19 +0000
In-Reply-To: <87h6wqmgio.ffs@tglx>
References: <20221124225331.464480443@linutronix.de>
         <20221124230314.337844751@linutronix.de>
         <1901d84f8f999ac6b2f067360f098828cb8c17cf.camel@infradead.org>
         <875yd6o2t7.ffs@tglx> <871qnunycr.ffs@tglx>
         <e12002af82e9554e42e876d7b9e813b90e673330.camel@infradead.org>
         <87h6wqmgio.ffs@tglx>
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On Mon, 2023-01-16 at 20:22 +0100, Thomas Gleixner wrote:
> > Tested-by: David Woodhouse <dwmw@amazon.co.uk>
> >=20
> > Albeit only under qemu with
> > https://git.infradead.org/users/dwmw2/qemu.git/shortlog/refs/heads/xenf=
v
> > and not under real Xen.
>=20
> Five levels of emulation. What could possibly go wrong?

It's the opposite =E2=80=94 this is what happened when I threw my toys out =
of
the pram and said, "You're NOT doing that with nested virtualization!".

One level of emulation. We host guests that think they're running on
Xen, directly in QEMU/KVM by handling the hypercalls and event
channels, grant tables, etc.

We virtualised Xen itself :)

Now you have no more excuses for breaking Xen guest mode!

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