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Date:   Wed, 12 Oct 2022 11:13:20 -0400
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Subject: Re: [PATCH 1/2] x86: Check return values from early_memremap calls
Content-Language: en-US
To:     Borislav Petkov <bp@alien8.de>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        dpsmith@apertussolutions.com, tglx@linutronix.de, mingo@redhat.com,
        hpa@zytor.com, luto@amacapital.net, dave.hansen@linux.intel.com,
        kanth.ghatraju@oracle.com, trenchboot-devel@googlegroups.com,
        Jan Kiszka <jan.kiszka@siemens.com>,
        jailhouse-dev@googlegroups.com, xen-devel@lists.xenproject.org,
        Andrew Cooper <andrew.cooper3@citrix.com>
References: <1650035401-22855-1-git-send-email-ross.philipson@oracle.com>
 <1650035401-22855-2-git-send-email-ross.philipson@oracle.com>
 <Y0GTUg1ACpKZYMHY@nazgul.tnic>
From:   Ross Philipson <ross.philipson@oracle.com>
In-Reply-To: <Y0GTUg1ACpKZYMHY@nazgul.tnic>
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On 10/8/22 11:12, Borislav Petkov wrote:
> Adding Xen and Jailhouse people and MLs to Cc.
> 
> Folks, thread starts here:
> 
> https://lore.kernel.org/r/1650035401-22855-1-git-send-email-ross.philipson@oracle.com
> 
> On Fri, Apr 15, 2022 at 11:10:00AM -0400, Ross Philipson wrote:
>> There are a number of places where early_memremap is called
>> but the return pointer is not checked for NULL. The call
>> can result in a NULL being returned so the checks must
>> be added.
>>
>> Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
>> ---
>>   arch/x86/kernel/devicetree.c | 10 ++++++++++
>>   arch/x86/kernel/e820.c       |  5 +++++
>>   arch/x86/kernel/jailhouse.c  |  6 ++++++
>>   arch/x86/kernel/mpparse.c    | 23 +++++++++++++++++++++++
>>   arch/x86/kernel/setup.c      |  5 +++++
>>   arch/x86/xen/enlighten_hvm.c |  2 ++
>>   arch/x86/xen/mmu_pv.c        |  8 ++++++++
>>   arch/x86/xen/setup.c         |  2 ++
>>   8 files changed, 61 insertions(+)
> 
> Ok, a couple of notes:
> 
> 1. the pr_*("<prefix>:" ... )
> 
> thing is done using pr_fmt() - grep the tree for examples.

I am already using the pr_* macros in the patches. Are you asking me to 
do something or is this just informational?

> 
> 2. I think you should not panic() the machine but issue a the
> warning/error and let the machine die a painful death anyway. But Xen
> folks will know better what would be the optimal thing to do.

When I was working on the patches I asked Andrew Cooper at Citrix what 
action I should take if any of the calls in the Xen code failed. I 
believe he told me it was basically fatal and that panic() would be fine 
there.

Thank you,
Ross Philipson

> 
> Thx.
>