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Subject: Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range}
To:     Bjorn Helgaas <helgaas@kernel.org>
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>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Sean Christopherson <seanjc@google.com>,
        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
        X86 ML <x86@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PCI <linux-pci@vger.kernel.org>,
        linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org,
        linux-parisc@vger.kernel.org, sparclinux@vger.kernel.org,
        linux-arch <linux-arch@vger.kernel.org>,
        Linux Doc Mailing List <linux-doc@vger.kernel.org>,
        virtualization@lists.linux-foundation.org,
        Rajat Jain <rajatja@google.com>
References: <20210824203115.GA3492097@bjorn-Precision-5520>
From:   Andi Kleen <ak@linux.intel.com>
Message-ID: <bb8c6f96-2597-bb80-bd08-7958405e1bf5@linux.intel.com>
Date:   Tue, 24 Aug 2021 13:50:00 -0700
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On 8/24/2021 1:31 PM, Bjorn Helgaas wrote:
> 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!

This is all in the patch intro too, which should make it into the merge 
commits.

I don't think we can reexplain the basic concepts for every individual 
patch in a large patch kit.


-Andi