Messages in this thread | | | From | Michael Kelley <> | Subject | RE: [PATCH v2] x86/mm: Don't disable INVLPG if "incomplete Global INVLPG flushes" is fixed by microcode | Date | Mon, 8 Apr 2024 23:31:25 +0000 |
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From: Dave Hansen <dave.hansen@intel.com> Sent: Thursday, April 4, 2024 11:09 AM > > On 4/4/24 10:48, Michael Kelley wrote: > > I agree one could argue that it is a hypervisor bug to present PCID to the guest > > in this situation. It's a lot cleaner to not have a guest be checking FMS and > > microcode versions. But whether that's practical in the real world, at least > > for Hyper-V, I don't know. What's the real impact of running with PCID while > > the flaw is still present? I don’t know the history here ... > > There's a chance that INVLPG will appear ineffective. > > The bad sequence would go something like this: The kernel does the > INVLPG on a global mapping. Later, when switching PCIDs, the TLB entry > mysteriously reappears. No PCIDs switching means no mysterious > reappearance.
Xi Ruoyao's patch identifies these errata: RPL042 and ADL063. In the links to the documents Xi provided, both of these errata have the following statement in the Errata Details section:
This erratum does not apply in VMX non-root operation. It applies only when PCIDs are enabled and either in VMX root operation or outside VMX operation.
I don't have deep expertise on the terminology here, but this sounds like it is saying the erratum doesn’t apply in a guest VM. Or am I misunderstanding?
Michael
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