linux-kernel - Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,

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Message-ID: <20210824203115.GA3492097@bjorn-Precision-5520>
Date:   Tue, 24 Aug 2021 15:31:15 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Richard Henderson <rth@...ddle.net>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        James E J Bottomley <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        "David S . Miller" <davem@...emloft.net>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Peter H Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        X86 ML <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        linux-alpha@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        Rajat Jain <rajatja@...gle.com>
Subject: Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range}

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