[PATCH kernel 2/2] powerpc/pseries/dma: Enable swiotlb

[Alexey Kardashevskiy]

On 11/05/2019 08:41, Thiago Jung Bauermann wrote:
> 
> Hello Alexey,
> 
> Thanks!
> 
> I have similar changes in my "Secure Virtual Machine Enablement"
> patches, which I am currently preparing for posting again real soon now.
> 
> This is the last version:
> 
> https://lore.kernel.org/linuxppc-dev/20180824162535.22798-1-bauerman@linux.ibm.com/
> 
> Alexey Kardashevskiy <aik at ozlabs.ru> writes:
> 
>> So far the pseries platforms has always been using IOMMU making SWIOTLB
>> unnecessary. Now we want secure guests which means devices can only
>> access certain areas of guest physical memory; we are going to use
>> SWIOTLB for this purpose.
>>
>> This allows SWIOTLB for pseries. By default there is no change in behavior.
>>
>> This enables SWIOTLB when the "swiotlb" kernel parameter is set to "force".
>>
>> With the SWIOTLB enabled, the kernel creates a directly mapped DMA window
>> (using the usual DDW mechanism) and implements SWIOTLB on top of that.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>> ---
>>  arch/powerpc/platforms/pseries/setup.c | 5 +++++
>>  arch/powerpc/platforms/pseries/Kconfig | 1 +
>>  2 files changed, 6 insertions(+)
>>
>> diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
>> index e4f0dfd4ae33..30d72b587ac5 100644
>> --- a/arch/powerpc/platforms/pseries/setup.c
>> +++ b/arch/powerpc/platforms/pseries/setup.c
>> @@ -42,6 +42,7 @@
>>  #include <linux/of.h>
>>  #include <linux/of_pci.h>
>>  #include <linux/memblock.h>
>> +#include <linux/swiotlb.h>
>>
>>  #include <asm/mmu.h>
>>  #include <asm/processor.h>
>> @@ -71,6 +72,7 @@
>>  #include <asm/isa-bridge.h>
>>  #include <asm/security_features.h>
>>  #include <asm/asm-const.h>
>> +#include <asm/swiotlb.h>
>>
>>  #include "pseries.h"
>>  #include "../../../../drivers/pci/pci.h"
>> @@ -797,6 +799,9 @@ static void __init pSeries_setup_arch(void)
>>  	}
>>
>>  	ppc_md.pcibios_root_bridge_prepare = pseries_root_bridge_prepare;
>> +
>> +	if (swiotlb_force == SWIOTLB_FORCE)
>> +		ppc_swiotlb_enable = 1;
>>  }
> 
> Yep! I have this here, enabled when booting as a secure guest:
> 
> https://lore.kernel.org/linuxppc-dev/20180824162535.22798-6-bauerman@linux.ibm.com/
> 
> And also another patch which makes it so that if booting as a secure
> guest it acts as if the swiotlb kernel parameter was set to force:
> 
> https://lore.kernel.org/linuxppc-dev/20180824162535.22798-11-bauerman@linux.ibm.com/
> 
>>  static void pseries_panic(char *str)
>> diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
>> index 9c6b3d860518..b9e8b608de01 100644
>> --- a/arch/powerpc/platforms/pseries/Kconfig
>> +++ b/arch/powerpc/platforms/pseries/Kconfig
>> @@ -23,6 +23,7 @@ config PPC_PSERIES
>>  	select ARCH_RANDOM
>>  	select PPC_DOORBELL
>>  	select FORCE_SMP
>> +	select SWIOTLB
>>  	default y
>>
>>  config PPC_SPLPAR
> 
> I put this in a PPC_SVM config option:
> 
> https://lore.kernel.org/linuxppc-dev/20180824162535.22798-3-bauerman@linux.ibm.com/


Well, my intention is to make it work regardless SVM, just to see if it
works and where the problems are if it does not (right now the NVIDIA
driver does not like SWIOTLB, debugging).



-- 
Alexey