Re: [Xen-devel] [PATCH V2] x86, amd_ucode: Safeguard against #GP

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.05.14 at 18:21, <andrew.cooper3@xxxxxxxxxx> wrote:
> The unhandled #GP fault certainly should be wrapped with wrmsr_safe(), 
> and an error/warning presented to the user.  In the case that a bad 
> ucode is discovered, it should be discarded and the server allowed to 
> boot.  It is substantially more useful for the server to come up and say 
> "I couldn't load that bit of microcode you wanted me to", than to sit in 
> a reboot loop because you made a typo in the bootloader config, and have 
> to get someone in the datacenter to poke the physical server.

But this isn't due to a typo somewhere, but due to a corrupted
microcode blob.

Besides that no matter which BKDG I look at, I can't seem to find any
indication of there being room for a #GP here if the MSR itself is
implemented. While I don't question its presence in reality, I'd prefer
if this was documented properly for a patch to recover from it to go
in.

Jan


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