linux-kernel - Re: [PATCH] pseries: Make CPU hotplug path endian safe

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Message-ID: <CAGZKiBpFoB2UrCPsEMHS-cJ-ffn1D7zcfznfp+P_gOGsigCPyg@mail.gmail.com>
Date:	Fri, 5 Sep 2014 21:03:11 +0530
From:	Bharata B Rao <bharata.rao@...il.com>
To:	Nathan Fontenot <nfont@...ux.vnet.ibm.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>
Subject: Re: [PATCH] pseries: Make CPU hotplug path endian safe

On Fri, Sep 5, 2014 at 7:38 PM, Nathan Fontenot
<nfont@...ux.vnet.ibm.com> wrote:
> On 09/05/2014 04:16 AM, bharata.rao@...il.com wrote:
>> From: Bharata B Rao <bharata@...ux.vnet.ibm.com>
>>
>> - ibm,rtas-configure-connector should treat the RTAS data as big endian.
>> - Treat ibm,ppc-interrupt-server#s as big-endian when setting
>>   smp_processor_id during hotplug.
>>
>> Signed-off-by: Bharata B Rao <bharata@...ux.vnet.ibm.com>
>> ---
>>  arch/powerpc/platforms/pseries/dlpar.c       | 10 +++++-----
>>  arch/powerpc/platforms/pseries/hotplug-cpu.c |  4 ++--
>>  2 files changed, 7 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c
>> index 2d0b4d6..dc55f9c 100644
>> --- a/arch/powerpc/platforms/pseries/dlpar.c
>> +++ b/arch/powerpc/platforms/pseries/dlpar.c
>> @@ -48,11 +48,11 @@ static struct property *dlpar_parse_cc_property(struct cc_workarea *ccwa)
>>       if (!prop)
>>               return NULL;
>>
>> -     name = (char *)ccwa + ccwa->name_offset;
>> +     name = (char *)ccwa + be32_to_cpu(ccwa->name_offset);
>>       prop->name = kstrdup(name, GFP_KERNEL);
>>
>> -     prop->length = ccwa->prop_length;
>> -     value = (char *)ccwa + ccwa->prop_offset;
>> +     prop->length = be32_to_cpu(ccwa->prop_length);
>> +     value = (char *)ccwa + be32_to_cpu(ccwa->prop_offset);
>>       prop->value = kmemdup(value, prop->length, GFP_KERNEL);
>>       if (!prop->value) {
>>               dlpar_free_cc_property(prop);
>> @@ -78,7 +78,7 @@ static struct device_node *dlpar_parse_cc_node(struct cc_workarea *ccwa,
>>       if (!dn)
>>               return NULL;
>>
>> -     name = (char *)ccwa + ccwa->name_offset;
>> +     name = (char *)ccwa + be32_to_cpu(ccwa->name_offset);
>>       dn->full_name = kasprintf(GFP_KERNEL, "%s/%s", path, name);
>>       if (!dn->full_name) {
>>               kfree(dn);
>> @@ -148,7 +148,7 @@ struct device_node *dlpar_configure_connector(u32 drc_index,
>>               return NULL;
>>
>>       ccwa = (struct cc_workarea *)&data_buf[0];
>> -     ccwa->drc_index = drc_index;
>> +     ccwa->drc_index = cpu_to_be32(drc_index);
>
> I need to look at this some more but I think this may cause an issue for
> partition migration. If I am following the code correctly, starting in
> pseries_devicetree_update(), the drc_index value passed to
> dlpar_configure_connector is pulled directly out of a buffer we get from
> firmware. This would mean the drc_index value is already in BE format.

Yes I see that now.

>
> Whereas for cpu hotplug the drc_index value is passed in from userspace
> via the cpu probe interface in sysfs. I assume that you are seeing the
> drc_index value getting passed in in LE format.

Yes I am seeing drc_index in LE format for an LE guest during CPU
hotplug operation.

Regards,
Bharata.
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