Re: [PATCH 2/2] x86/dmar: zap DMAR signature for dom0 once in TBOOT case

[Zhenzhong Duan <zhenzhong.duan@oracle.com>]

On 2018/8/20 16:30, Jan Beulich wrote:
>>>> On 20.08.18 at 05:32, <zhenzhong.duan@oracle.com> wrote:
>> When TBOOT enabled, acpi_parse_dmar() zap a copy of DMAR table rather
>> than the real table, so make it controled by config option based on the
>> fact that we already have done the real zapping in tboot_parse_dmar_table().
> 
> Is this just a cosmetic change, or is there any harm done by the extra
> zapping?
Cosmetic change, I feel it isn't necessory to zap a copy of DMAR table 
which is freed later.

Thanks
Zhenzhong
> 
>> As said above, acpi_parse_dmar() doesn't zaps APCI DMAR signature in
>> real TXT heap table, fix the stale comments.
>>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
>> ---
>>   xen/arch/x86/tboot.c               |    3 +--
>>   xen/drivers/passthrough/vtd/dmar.c |    2 ++
>>   2 files changed, 3 insertions(+), 2 deletions(-)
> 
> You've again failed to Cc maintainers (included now).
> 
> Jan
> 
>> --- a/xen/arch/x86/tboot.c
>> +++ b/xen/arch/x86/tboot.c
>> @@ -490,8 +490,7 @@ int __init tboot_parse_dmar_table(acpi_table_handler dmar_handler)
>>       rc = dmar_handler(dmar_table);
>>       xfree(dmar_table);
>>   
>> -    /* acpi_parse_dmar() zaps APCI DMAR signature in TXT heap table */
>> -    /* but dom0 will read real table, so must zap it there too */
>> +    /* Dom0 will read real DMAR table, so must zap it there */
>>       acpi_dmar_zap();
>>   
>>       return rc;
>> --- a/xen/drivers/passthrough/vtd/dmar.c
>> +++ b/xen/drivers/passthrough/vtd/dmar.c
>> @@ -866,8 +866,10 @@ static int __init acpi_parse_dmar(struct acpi_table_header *table)
>>       }
>>   
>>   out:
>> +#ifndef CONFIG_TBOOT
>>       /* Zap ACPI DMAR signature to prevent dom0 using vt-d HW. */
>>       acpi_dmar_zap();
>> +#endif
>>       return ret;
>>   }
>>   
> 
> 

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