From mboxrd@z Thu Jan  1 00:00:00 1970
From: Bjorn Helgaas <helgaas@kernel.org>
Subject: Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range}
Date: Tue, 24 Aug 2021 15:31:15 -0500
Message-ID: <20210824203115.GA3492097@bjorn-Precision-5520>
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To: Andi Kleen <ak@linux.intel.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Dan Williams <dan.j.williams@intel.com>, "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Peter Zijlstra <peterz@infradead.org>, Andy Lutomirski <luto@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>, Richard Henderson <rth@twiddle.net>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, James E J Bottomley <James.Bottomley@hansenpartnership.com>, Helge Deller <deller@gmx.de>, "David S . Miller" <davem@davemloft.net>, Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>, Peter H Anvin <hpa@zytor.com>, Dave Hansen <dave.hansen@intel.com>, Tony Luck <tony.luck@intel.com>

On Tue, Aug 24, 2021 at 01:14:02PM -0700, Andi Kleen wrote:
> 
> On 8/24/2021 11:55 AM, Bjorn Helgaas wrote:
> > [+cc Rajat; I still don't know what "shared memory with a hypervisor
> > in a confidential guest" means,
> 
> A confidential guest is a guest which uses memory encryption to isolate
> itself from the host. It doesn't trust the host. But it still needs to
> communicate with the host for IO, so it has some special memory areas that
> are explicitly marked shared. These are used to do IO with the host. All
> their usage needs to be carefully hardened to avoid any security attacks on
> the guest, that's why we want to limit this interaction only to a small set
> of hardened drivers. For MMIO, the set is currently only virtio and MSI-X.

Good material for the commit log next time around.  Thanks!

Bjorn