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Re: powerpc/nvram: Fix an incorrect partition merge

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  Re: powerpc/nvram: Fix an incorrect partition merge Michael Ellerman <mpe@ellerman.id.au> - 2016-06-03 13:50 +0200
    Re: powerpc/nvram: Fix an incorrect partition merge xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-06 07:40 +0200
      Re: powerpc/nvram: Fix an incorrect partition merge Stewart Smith <stewart@linux.vnet.ibm.com> - 2016-06-07 07:30 +0200
      Re: powerpc/nvram: Fix an incorrect partition merge Michael Ellerman <mpe@ellerman.id.au> - 2016-06-07 13:40 +0200

#1413148 — Re: powerpc/nvram: Fix an incorrect partition merge

On Thu, 2015-10-12 at 07:30:02 UTC, xinhui wrote:
> From: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
> 
> When we merge two contiguous partitions whose signatures are marked
> NVRAM_SIG_FREE, We need update prev's length and checksum, then write it
> to nvram, not cur's. So lets fix this mistake now.
> 
> Also use memset instead of strncpy to set the partition's name. It's
> more readable if we want to fill up with duplicate chars .

Does this ever happen in practice? ie. should we backport the fix to stable
kernels?

Has it always been broken?

cheers

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#1414652

On 2016年06月03日 19:47, Michael Ellerman wrote:
> On Thu, 2015-10-12 at 07:30:02 UTC, xinhui wrote:
>> From: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
>>
>> When we merge two contiguous partitions whose signatures are marked
>> NVRAM_SIG_FREE, We need update prev's length and checksum, then write it
>> to nvram, not cur's. So lets fix this mistake now.
>>
>> Also use memset instead of strncpy to set the partition's name. It's
>> more readable if we want to fill up with duplicate chars .
>
> Does this ever happen in practice? ie. should we backport the fix to stable
> kernels?
>

I did not see that nvram warning in practice. BUT I suggest to backport it to stable kernel. :)

Let me recall the story. :)
In past days, I was using pstore to keep some kernel logs. and sometimes I found my own logs and the panic logs did not show.
pstore use a fixed-address reserved memory In x86 while nvram instead in ppc.

Then I spent some days to review the nvram codes.
And worked out three patches to fix all issues that I found in nvram. BUT looks like I only sent out two of them. :)
I lost the third patch maybe...

> Has it always been broken?
>

no. after nvram partition corruption hit, all nvram partitions will be erased and re-alloc after the second machine reboot.
I don't know who does it but i guess it is the firmware. :)

thanks
xinhui
> cheers
>

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#1415706

xinhui <xinhui.pan@linux.vnet.ibm.com> writes:
>> Has it always been broken?
>>
>
> no. after nvram partition corruption hit, all nvram partitions will be
> erased and re-alloc after the second machine reboot.
> I don't know who does it but i guess it is the firmware. :)

It is. PAPR says we format NVRAM when it's corrupted. This is also true
for NVRAM for PowerNV (not just pseries guest).

-- 
Stewart Smith
OPAL Architect, IBM.

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#1416052

On Mon, 2016-06-06 at 13:31 +0800, xinhui wrote:
> On 2016年06月03日 19:47, Michael Ellerman wrote:
> > On Thu, 2015-10-12 at 07:30:02 UTC, xinhui wrote:
> > > From: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
> > > 
> > > When we merge two contiguous partitions whose signatures are marked
> > > NVRAM_SIG_FREE, We need update prev's length and checksum, then write it
> > > to nvram, not cur's. So lets fix this mistake now.
> > > 
> > > Also use memset instead of strncpy to set the partition's name. It's
> > > more readable if we want to fill up with duplicate chars .
> > 
> > Does this ever happen in practice? ie. should we backport the fix to stable
> > kernels?
> 
> I did not see that nvram warning in practice. BUT I suggest to backport it to stable kernel. :)
> 
> Let me recall the story. :)
> In past days, I was using pstore to keep some kernel logs. and sometimes I found my own logs and the panic logs did not show.
> pstore use a fixed-address reserved memory In x86 while nvram instead in ppc.
> 
> Then I spent some days to review the nvram codes.
> And worked out three patches to fix all issues that I found in nvram. BUT looks like I only sent out two of them. :)
> I lost the third patch maybe...

OK.

> > Has it always been broken?
> 
> no. after nvram partition corruption hit, all nvram partitions will be erased and re-alloc after the second machine reboot.
> I don't know who does it but i guess it is the firmware. :)

Actually I meant has the code always contained the bug, or was it added recently.

cheers

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