Re: [kvm-unit-tests PATCH] x86/emulator: Test POP-SS blocking

Nadav Amit
2022-08-22T18:31:18Z

On Aug 22, 2022, at 8:42 AM, Sean Christopherson <seanjc@google.com> wrote:

> On Mon, Aug 22, 2022, Michal Luczaj wrote:
>> On 8/22/22 00:06, Michal Luczaj wrote:
>>> Note that doing this the ASM_TRY() way would require extending
>>> setup_idt() (to handle #DB) and introducing another ASM_TRY() variant
>>> (one without the initial `movl $0, %%gs:4`).
>>
>> Replying to self as I was wrong regarding the need for another ASM_TRY() variant.
>> Once setup_idt() is told to handle #DB,
>
> Hmm, it might be a moot point for this patch (see below), but my vote is to have
> setup_idt() wire up all known handlers to check_exception_table(). I don't see
> any reason to skip some vectors. Code with __ASM_TRY() will explode no matter what,
> so it's not like it risks suppressing completely unexpected faults.

I would just like to point out that this whole FEP approach is not friendly
for other hypervisors or bare-metal testings. While people might have mixed
feelings about other hypervisors, the benefit of running the tests on
bare-metal should be clear.

Specifically in this test, it is rather simple to avoid using FEP.

Oh, well.