Re: [PATCH v7 06/12] KVM: guest_memfd: add module param for disabling TLB flushing

Dave Hansen
2025-09-25T19:59:17Z

On 9/25/25 12:20, David Hildenbrand wrote:
> On 25.09.25 20:27, Dave Hansen wrote:
>> On 9/24/25 08:22, Roy, Patrick wrote:
>>> Add an option to not perform TLB flushes after direct map manipulations.
>>
>> I'd really prefer this be left out for now. It's a massive can of worms.
>> Let's agree on something that works and has well-defined behavior before
>> we go breaking it on purpose.
>
> May I ask what the big concern here is?

It's not a _big_ concern. I just think we want to start on something
like this as simple, secure, and deterministic as possible.

Let's say that with all the unmaps that load_unaligned_zeropad() faults
start to bite us. It'll take longer to find them if the TLB isn't flushed.

Basically, it'll make the bad things happen sooner rather than later.