Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory

On Tue, Sep 13, 2022 at 02:53:25PM +0000, Sean Christopherson wrote:

quoted

quoted

Switching topics, what actually prevents mmapp() on the shim?  I tried to follow,
but I don't know these areas well enough.

It has no f_op->mmap, so mmap() will fail with -ENODEV. See do_mmap().
(I did not read the switch statement correctly at first. Note there are
two 'fallthrough' there.)

Ah, validate_mmap_request().  Thought not implementing ->mmap() was the key, but
couldn't find the actual check.

validate_mmap_request() is in mm/nommu.c which is not relevant for real
computers.

I was talking about this check:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/mmap.c#n1495

-- 
  Kiryl Shutsemau / Kirill A. Shutemov