Originally posted by Alex/AT
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Oracle Proposing Change To Linux's KPTI Meltdown Mitigation
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Originally posted by RahulSundaram View PostThat does not have any impact on upstream kernel.
The biggest impact is in different place, not even in performance, but horrible performance being the reason of it.
It is a horrific set of crutches on duct tape right in the very heart of the kernel.
Starting from syscalls and memory management and ending in interrupt handling.
Whether it will shoot everyone in the leg one day or not, that's not clear yet.
Oracle attempt on amending it by adding more crutches and more tape is just another proof it should.Last edited by Alex/AT; 10 November 2020, 04:48 PM.
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What is the state of PCID (Process Context IDentifier) support in Linux? The feature (the /proc/cpuinfo flag is called INVPCID) has been available on Intel processors since quite a while and is present in AMD new Zen 3 architecture. It seems to me it's a good fir for KPTI.
Also, support for it was available in VirtualBox on Windows (via a VBoxManage command). I wonder if KVM can do the same.
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Originally posted by Alex/AT View PostYeah, nobody could live without PTI before it existed and surely no one disables it now.
(as if)
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Originally posted by Alex/AT View PostYou actually can. This will force either throwing out hardware, or accepting the risks.
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Originally posted by Alex/AT View PostOkay. Next step: accepting Intel CPUs are vulnerable and throwing the mitigations out in favor of proper fix
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Okay. Next step: accepting Intel CPUs are vulnerable and throwing the mitigations out in favor of proper fix
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Oracle Proposing Change To Linux's KPTI Meltdown Mitigation
Phoronix: Oracle Proposing Change To Linux's KPTI Meltdown Mitigation
A proposal and set of patches have been sent out around the Linux kernel's Page Table Isolation (PTI/KPTI) implementation to defer switching from the user page-table to kernel page-table until later in the kernel entry sequence. There are possible performance benefits and code improvements that would stem from this change...
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