[6.4-rc6] Crash during a kexec operation (tpm_amd_is_rng_defective)

[Sachin Sant]

> On 22-Jun-2023, at 8:08 PM, Limonciello, Mario <Mario.Limonciello at amd.com> wrote:
> 
> 
> On 6/22/2023 7:36 AM, Michael Ellerman wrote:
>> "Linux regression tracking (Thorsten Leemhuis)" <regressions at leemhuis.info> writes:
>>> Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting
>>> for once, to make this easily accessible to everyone.
>>> 
>>> As Linus will likely release 6.4 on this or the following Sunday a quick
>>> question: is there any hope this regression might be fixed any time
>>> soon?
>> No.
>> 
>> I have added the author of the commit to Cc, maybe they can help?
>> 
>> The immediate question is, is it expected for chip->ops to be NULL in
>> this path? Obviously on actual AMD systems that isn't the case,
>> otherwise the code would crash there. But is the fact that chip->ops is
>> NULL a bug in the ibmvtpm driver, or a possibility that has been
>> overlooked by the checking code.
>> 
>> cheers
> 
> All that code assumes that the TPM is still functional which
> seems not to be the case for your TPM.
> 
> This should fix it:

Yes, with this change kexec works correctly.

Since Aneesh first reported this problem including reported by credit for him

Reported-by: Aneesh Kumar K. V <aneesh.kumar at linux.ibm.com>
Reported-by: Sachin Sant <sachinp at linux.ibm.com>
Tested-by: Sachin Sant <sachinp at linux.ibm.com>

-Sachin