Re: [PATCH for-4.10 2/2] xen/arm: p2m: Add more debug in get_page_from_gva

[Julien Grall <julien.grall@linaro.org>]

On 11/16/2017 01:36 AM, Stefano Stabellini wrote:
> On Wed, 15 Nov 2017, Julien Grall wrote:
>> The function get_page_from_gva is used by copy_*_guest helpers to
>> translate a guest virtual address to a machine physical address and take
>> reference on the page.
>>
>> There are a couple of errors path that will return the same value making
>                                 ^ paths
> 
>> difficult to know the exact error. Add more debug in each error patch
> ^ it difficult
> 
> 
>> only for debug-build.
>>
>> This should help narrowing down the intermittent failure with the
>> hypercall GNTTABOP_copy (see [1]).
>>
>> [1] https://lists.xen.org/archives/html/xen-devel/2017-11/msg00942.html
>>
>> Signed-off-by: Julien Grall <julien.grall@linaro.org>
> 
> Acked-by: Stefano Stabellini <sstabellini@kernel.org>
> 
> fixed on commit

I am not sure why this was merged given Andrew gave some comments...

> 
> 
>> ---
>>   xen/arch/arm/p2m.c | 13 +++++++++++++
>>   1 file changed, 13 insertions(+)
>>
>> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
>> index f6b3d8e421..417609ede2 100644
>> --- a/xen/arch/arm/p2m.c
>> +++ b/xen/arch/arm/p2m.c
>> @@ -1428,16 +1428,29 @@ struct page_info *get_page_from_gva(struct vcpu *v, vaddr_t va,
>>       par = gvirt_to_maddr(va, &maddr, flags);
>>   
>>       if ( par )
>> +    {
>> +        dprintk(XENLOG_G_DEBUG,
>> +                "%pv: gvirt_to_maddr failed va=%#"PRIvaddr" flags=0x%lx par=%#"PRIx64"\n",
>> +                v, va, flags, par);
>>           goto err;
>> +    }
>>   
>>       if ( !mfn_valid(maddr_to_mfn(maddr)) )
>> +    {
>> +        dprintk(XENLOG_G_DEBUG, "%pv: Invalid MFN %#"PRI_mfn"\n",
>> +                v, mfn_x(maddr_to_mfn(maddr)));
>>           goto err;
>> +    }
>>   
>>       page = mfn_to_page(maddr_to_mfn(maddr));
>>       ASSERT(page);
>>   
>>       if ( unlikely(!get_page(page, d)) )
>> +    {
>> +        dprintk(XENLOG_G_DEBUG, "%pv: Failing to acquire the MFN %#"PRI_mfn"\n",
>> +                v, mfn_x(maddr_to_mfn(maddr)));
>>           page = NULL;
>> +    }
>>   
>>   err:
>>       if ( !page && p2m->mem_access_enabled )

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