Linus Torvalds writes: (Summary) But again, that is something that some people may be perfectly
fine with - it's certainly much less of an issue than leaking actual
*data*.
*data*.
And it might be an easy option to give people, with something like "pti=data" or similar.
"pti=data" or similar.
It's also quite possible that depending on how separate the ITLB and DTLB is, an ITLB entry might not even really be amenable to Meltdown leaking at all.
leaking at all.
Since the pages wouldn't actually exist in the user page tables, the only sign of them would be in the TLB entries, and if the ITLB is separate enough it might be practically impossible to really use those ITLB entries for meltdown.
ITLB entries for meltdown.
Of course, maybe the performance advantage from keeping the ITLB entries around isn't huge, but this *may* be worth at least asking some Intel architects about?
some Intel architects about?
Because my gut feel is that a noticeable amount of the TLB cost from PTI comes from the code
*data*.
And it might be an easy option to give people, with something like "pti=data" or similar.
"pti=data" or similar.
It's also quite possible that depending on how separate the ITLB and DTLB is, an ITLB entry might not even really be amenable to Meltdown leaking at all.
leaking at all.
Since the pages wouldn't actually exist in the user page tables, the only sign of them would be in the TLB entries, and if the ITLB is separate enough it might be practically impossible to really use those ITLB entries for meltdown.
ITLB entries for meltdown.
Of course, maybe the performance advantage from keeping the ITLB entries around isn't huge, but this *may* be worth at least asking some Intel architects about?
some Intel architects about?
Because my gut feel is that a noticeable amount of the TLB cost from PTI comes from the code