On 10/4/22 11:02 AM, Robin Murphy wrote:
> On 2022-10-04 13:07, Niklas Schnelle wrote:
>> The .pgsize_bitmap property of struct iommu_ops is not a page mask but
>> rather has a bit set for each size of pages the IOMMU supports. As the
>> comment correctly pointed out at this moment the code only support 4K
>> pages so simply use SZ_4K here.
>
> Unless it's already been done somewhere else, you'll want to switch over to the {map,unmap}_pages() interfaces as well to avoid taking a hit on efficiency here. The "page mask" thing was an old hack to trick the core API into making fewer map/unmap calls where the driver could map arbitrary numbers of pages at once anyway. The multi-page interfaces now do that more honestly and generally better (since they work for non-power-of-two sizes as well).
Thanks for the heads up -- Niklas has some additional series coming soon as described here:
https://lore.kernel.org/linux-iommu/a10424adbe01a0fd40372cbd0736d11e517951a1.camel@xxxxxxxxxxxxx/
So implementing the _pages() interfaces is soon up on the roadmap. But given what you say I wonder if this patch should just wait until the series that implements {map,unmap}_pages().
>
> Robin.
>
>> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
>> Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
>> ---
>> drivers/iommu/s390-iommu.c | 9 +--------
>> 1 file changed, 1 insertion(+), 8 deletions(-)
>>
>> diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
>> index 94c444b909bd..6bf23e7830a2 100644
>> --- a/drivers/iommu/s390-iommu.c
>> +++ b/drivers/iommu/s390-iommu.c
>> @@ -12,13 +12,6 @@
>> #include <linux/sizes.h>
>> #include <asm/pci_dma.h>
>> -/*
>> - * Physically contiguous memory regions can be mapped with 4 KiB alignment,
>> - * we allow all page sizes that are an order of 4KiB (no special large page
>> - * support so far).
>> - */
>> -#define S390_IOMMU_PGSIZES (~0xFFFUL)
>> -
>> static const struct iommu_ops s390_iommu_ops;
>> struct s390_domain {
>> @@ -350,7 +343,7 @@ static const struct iommu_ops s390_iommu_ops = {
>> .probe_device = s390_iommu_probe_device,
>> .release_device = s390_iommu_release_device,
>> .device_group = generic_device_group,
>> - .pgsize_bitmap = S390_IOMMU_PGSIZES,
>> + .pgsize_bitmap = SZ_4K,
>> .get_resv_regions = s390_iommu_get_resv_regions,
>> .default_domain_ops = &(const struct iommu_domain_ops) {
>> .attach_dev = s390_iommu_attach_device,
