Messages in this thread | | | Date | Mon, 11 Sep 2023 10:09:44 +0200 | Subject | Re: [PATCH 3/3] /dev/mem: Do not map unaccepted memory | From | David Hildenbrand <> |
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On 07.09.23 16:46, Dave Hansen wrote: > On 9/7/23 07:25, Kirill A. Shutemov wrote: >> On Thu, Sep 07, 2023 at 07:15:21AM -0700, Dave Hansen wrote: >>> On 9/6/23 00:39, Adrian Hunter wrote: >>>> Support for unaccepted memory was added recently, refer commit >>>> dcdfdd40fa82 ("mm: Add support for unaccepted memory"), whereby >>>> a virtual machine may need to accept memory before it can be used. >>>> >>>> Do not map unaccepted memory because it can cause the guest to fail. >>> Doesn't /dev/mem already provide a billion ways for someone to shoot >>> themselves in the foot? TDX seems to have added the 1,000,000,001st. >>> Is this really worth patching? >> Is it better to let TD die silently? I don't think so. > > First, let's take a look at all of the distro kernels that folks will > run under TDX. Do they have STRICT_DEVMEM set?
For virtio-mem, we do
config VIRTIO_MEM ... depends on EXCLUSIVE_SYSTEM_RAM
Which in turn:
config EXCLUSIVE_SYSTEM_RAM ... depends on !DEVMEM || STRICT_DEVMEM
Not supported on all archs, but at least on RHEL9 on x86_64 and aarch64.
So, making unaccepted memory similarly depend on "!DEVMEM || STRICT_DEVMEM" does not sound too far off ...
-- Cheers,
David / dhildenb
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