Messages in this thread | | | Date | Sat, 6 Jan 2024 17:50:23 +0000 | From | Oliver Upton <> | Subject | Re: [RFC PATCH] KVM: arm64: Workaround for Ampere AC03_CPU_36 (exception taken to an incorrect EL) |
| |
On Sat, Jan 06, 2024 at 12:13:09PM +0000, Marc Zyngier wrote:
[...]
> > From 265cb193190c13c651d8e008d34d1d18505d4804 Mon Sep 17 00:00:00 2001 > > From: Oliver Upton <oliver.upton@linux.dev> > > Date: Fri, 5 Jan 2024 23:18:14 +0000 > > Subject: [PATCH] KVM: arm64: Mitigate AmpereOne erratum AC03_CPU_36 > > > > The AmpereOne design suffers from an erratum where if an asynchronous > > exception arrives while EL2 is modifying hypervisor exception controls > > (i.e. HCR_EL2, SCTLR_EL2) the PE may take an invalid exception to > > another EL. > > Same questions about SCTLR_EL2 and the notion of "another EL".
I've got the same questions :) This is just a rewording of Ampere's erratum description.
https://amperecomputing.com/customer-connect/products/AmpereOne-device-documentation
> Other than the passing comments, I'm OK with this patch. However, I am > very worried that this is only the start of a very long game of > whack-a-mole, because there is no actual documentation on what goes > wrong. > > For example, we have plenty of writes to SCTLR_EL2 (using the > SCTLR_EL1 alias if running VHE) for MTE. Are any of those affected? > > Short of having some solid handle on what is happening, I don't see > how we can promise to support this system.
Completely agree. At least on the AmpereOne machines I have access to this seems to do the trick, but that observation is no replacement for full documentation.
-- Thanks, Oliver
| |