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:

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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/m...