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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Resume from suspend to RAM broken when using early microcode updates
>>> On 11.04.18 at 13:51, <andrew.cooper3@xxxxxxxxxx> wrote: > On 11/04/18 12:48, Simon Gaiser wrote: >> Hi, >> >> when I use early microcode loading with the microcode update with the >> BTI mitigations, resuming from suspend to RAM is broken. >> >> Based on added logging to enter_state() (from power.c) it doesn't >> survive the local_irq_restore(flags) call (at least a printk() after the >> call doesn't output anything on the serial console). >> >> I guess that some irq handler tries to use IBRS/IBPB. But the microcode >> is only loaded later. >> >> If I simply move the microcode_resume_cpu(0) directly before the >> local_irq_restore(flags) everything seems to work fine. But I'm not sure >> if this has unintended consequences. >> >> I tested the above with Xen 4.8.3 from Qubes which includes the BTI and >> microcode patches from staging-4.8. AFAICS there are no commits which >> changes the affected code or other commits which sound relevant so this >> probably affected also all the newer branches. > > S3 support is a very unloved area of the hypervisor. > > Yes - we definitely need to get microcode reloaded before interrupts are > enabled. That said, I would have expected a backtrace complaining about > a GP fault if we had hit the use of IBRS/IBPB before the microcode was > reloaded. Wouldn't the #GP handling re-raise a #GP for the same reason, until hitting the end of the stack, making it a #DF, the handler of which would yet again have the same issue? This would end with an infinite loop between #GP and #DF handlers (never triple faulting), and no output. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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