Messages in this thread | | | Date | Fri, 11 Mar 2022 18:06:49 +0100 | From | Joerg Roedel <> | Subject | Re: [PATCH v12 32/46] x86/compressed/64: Add support for SEV-SNP CPUID table in #VC handlers |
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On Thu, Mar 10, 2022 at 03:25:04PM -0600, Michael Roth wrote: > Joerg, do you have more background on that? Would it make sense, outside > of this series, to change it to a terminate? Maybe with a specific set > of error codes for ES_{OK,UNSUPPORTED,VMM_ERROR,DECODE_FAILED}?
This seems to be a left over from development of the SEV-ES guest patch-set. I wanted to see whether the VM crashed due to a triple fault or an error in the #VC handler. The halt loop can be replaced by termination request now.
> > I am still working on why the early_printk()s in that function are not > > working, it seems that they lead to a different halt. > > I don't see a different halt. They just don't seem to print anything. > (keep in mind you still need to advance the IP or else the guest is > still gonna end up spinning here, even if you're removing the halt loop > for testing purposes)
The early_printks() also cause #VC exceptions, and if that handling is broken for some reason nothing will be printed.
> > > working, it seems that they lead to a different halt. Have you tested > > any of those error paths manually? For example if you set your CPUID > > bits to explicitly fail here do you see the expected printks? > > I think at that point in the code, when the XSAVE stuff is setup, the > console hasn't been enabled yet, so messages would get buffered until they > get flushed later (which won't happen since there's halt loop after). I > know in some cases devs will dump the log buffer from memory instead to get > at the error messages for early failures. (Maybe that's also why Joerg > decided to use a halt loop there instead of terminating?)
It is hard to dump the log-buffer from encrypted memory :) But I remember having seen messages from these early_printks under SEV-ES for different bugs. Not sure why they don't appear in this situation.
> So maybe reworking the error handling in handle_vc_boot_ghcb() to use > sev_es_terminate() might be warranted, but probably worth checking with > Joerg first, and should be done as a separate series since it is not > SNP-related.
I am fine with this change.
Regards,
-- Jörg Rödel jroedel@suse.de
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