Re: [PATCH v1 11/26] x86/sev: Invalidate pages from the direct map when adding them to the RMP table

Vlastimil Babka
2024-01-15T09:23:20Z

On 1/12/24 21:37, Dave Hansen wrote:
> On 1/12/24 12:28, Tom Lendacky wrote:
>> I thought there was also a desire to remove the direct map for any pages
>> assigned to a guest as private, not just the case that the comment says.
>> So updating the comment would probably the best action.
>
> I'm not sure who desires that.
>
> It's sloooooooow to remove things from the direct map. There's almost
> certainly a frequency cutoff where running the whole direct mapping as
> 4k is better than the cost of mapping/unmapping.
>
> Actually, where _is_ the TLB flushing here?

Hm yeah it seems to be using the _noflush version? Maybe the RMP issues this
avoids are only triggered with actual page tables and a stray outdated TLB
hit doesn't trigger it? Needs documenting though if that's the case.