Re: [PATCH 2/2] hw/arm/smmu-common: Fix TTB1 handling

[Eric Auger]

On 2/14/23 17:46, Jean-Philippe Brucker wrote:
> On Mon, Feb 13, 2023 at 05:30:03PM +0100, Eric Auger wrote:
>> Hi Jean,
>>
>> On 2/10/23 17:37, Jean-Philippe Brucker wrote:
>>> Addresses targeting the second translation table (TTB1) in the SMMU have
>>> all upper bits set (except for the top byte when TBI is enabled). Fix
>>> the TTB1 check.
>>>
>>> Reported-by: Ola Hugosson <ola.hugosson@arm.com>
>>> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
>>> ---
>>>  hw/arm/smmu-common.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/hw/arm/smmu-common.c b/hw/arm/smmu-common.c
>>> index 2b8c67b9a1..0a5a60ca1e 100644
>>> --- a/hw/arm/smmu-common.c
>>> +++ b/hw/arm/smmu-common.c
>>> @@ -249,7 +249,7 @@ SMMUTransTableInfo *select_tt(SMMUTransCfg *cfg, 
>>> dma_addr_t iova)
>>>          /* there is a ttbr0 region and we are in it (high bits all zero) */
>>>          return &cfg->tt[0];
>>>      } else if (cfg->tt[1].tsz &&
>>> -           !extract64(iova, 64 - cfg->tt[1].tsz, cfg->tt[1].tsz - 
>>> tbi_byte)) {
>>> +        sextract64(iova, 64 - cfg->tt[1].tsz, cfg->tt[1].tsz - tbi_byte) 
>>> == -1) {
>>>          /* there is a ttbr1 region and we are in it (high bits all one) */
>>>          return &cfg->tt[1];
>>>      } else if (!cfg->tt[0].tsz) {
>> Reviewed-by: Eric Auger <eric.auger@redhat.com>
>>
>> While reading the spec again, I noticed we do not support VAX. Is it
>> something that we would need to support?
> I guess it would be needed to support sharing page tables with the CPU, if
> the CPU supports and the OS uses FEAT_LVA. But in order to share the
> stage-1, Linux would need more complex features as well (ATS+PRI/Stall,
> PASID).
>
> For a private DMA address space, I think 48 bits of VA is already plenty.

OK thanks!

Eric
>
> Thanks,
> Jean
>