[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2] xen/arm: do not read MVFR2 when is not defined
On 08.01.2021 20:22, Stefano Stabellini wrote: > MVFR2 is not available on ARMv7. It is available on ARMv8 aarch32 and > aarch64. If Xen reads MVFR2 on ARMv7 it could crash. > > Avoid the issue by doing the following: > > - define MVFR2_MAYBE_UNDEFINED on arm32 > - if MVFR2_MAYBE_UNDEFINED, do not attempt to read MVFR2 in Xen > - keep the 3rd register_t in struct cpuinfo_arm.mvfr on arm32 so that a > guest read to the register returns '0' instead of crashing the guest. > > '0' is an appropriate value to return to the guest because it is defined > as "no support for miscellaneous features". > > Aarch64 Xen is not affected by this patch. But it looks to also be affected by ... > Fixes: 9cfdb489af81 ("xen/arm: Add ID registers and complete cpuinfo") ... this, faulting (according to osstest logs) early during boot on 000000000025D314 mrs x1, id_pfr2_el1 afaict. Jan
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