linux-kernel - Re: [6.4-rc6] Crash during a kexec operation (tpm_amd_is_rng

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Date:   Fri, 23 Jun 2023 08:22:04 +0530
From:   Sachin Sant <sachinp@...ux.ibm.com>
To:     "Limonciello, Mario" <Mario.Limonciello@....com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Linux regressions mailing list <regressions@...ts.linux.dev>,
        open list <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, jarkko@...nel.org,
        linux-integrity@...r.kernel.org,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
Subject: Re: [6.4-rc6] Crash during a kexec operation
 (tpm_amd_is_rng_defective)



> On 22-Jun-2023, at 8:08 PM, Limonciello, Mario <Mario.Limonciello@....com> wrote:
> 
> 
> On 6/22/2023 7:36 AM, Michael Ellerman wrote:
>> "Linux regression tracking (Thorsten Leemhuis)" <regressions@...mhuis.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@...ux.ibm.com>
Reported-by: Sachin Sant <sachinp@...ux.ibm.com>
Tested-by: Sachin Sant <sachinp@...ux.ibm.com>

-Sachin