Date:   Wed, 08 Mar 2023 01:59:46 +0000
In-Reply-To: <20230307021809.GA2143916@chaop.bj.intel.com> (message from Chao
 Peng on Tue, 7 Mar 2023 10:18:09 +0800)
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Message-ID: <diqz356guhnx.fsf@ackerleytng-cloudtop.c.googlers.com>
Subject: Re: [V2 PATCH 0/6] KVM: selftests: selftests for fd-based private memory
From:   Ackerley Tng <ackerleytng@google.com>
To:     Chao Peng <chao.p.peng@linux.intel.com>
Cc:     vannapurve@google.com, seanjc@google.com, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
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        bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com,
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        jlayton@kernel.org, bfields@fieldses.org,
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Chao Peng <chao.p.peng@linux.intel.com> writes:

>> [...]

>> Chao, I'll work on

>> + Running conversion tests for non-overlapping GPA ranges of
>>    same/different memslots from multiple vcpus
>> + Deleting memslots with restricted memfd while guests are being
>>    executed
>> + Installing multiple memslots with ranges within the same restricted
>>    mem files

>> this week.

> Thanks Ackerley. Looks good to me.

> BTW, for whom may have interest, below are the testcases I added:
> https://github.com/chao-p/linux/commit/24dd1257d5c93acb8c8cc6c76c51cf6869970f8a
> https://github.com/chao-p/linux/commit/39a872ef09d539ce0c953451152eb05276b87018
> https://github.com/chao-p/linux/commit/ddd2c92b268a2fdc6158f82a6169ad1a57f2a01d

> Chao

Hi Chao,

While I was working on the selftests I noticed that this could perhaps
be improved:

https://github.com/chao-p/linux/blob/ddd2c92b268a2fdc6158f82a6169ad1a57f2a01d/virt/kvm/kvm_main.c#L1035

We should use a temporary variable to hold the result of fget(fd).

As it is now, if the user provides any invalide fd, like -1,
slot->restrictedmem.file would be overwritten and lost.

We cannot update slot->restrictedmem.file until after the
file_is_restrictedmem() check.

For now there isn't a big problem because kvm_restrictedmem_bind() is
only called on a new struct kvm_memory_slot, but I think this should be
changed in case the function is used elsewhere in future.

Ackerley