Hi Lu Baolu, I tried kernel 4.18.0-147.6.el8.x86_64+debug and used the following API sequence for mapping multiple hugepages:
get_user_pages_fast() sg_alloc_table_from_pages() // also tried sg_alloc_table() w/ sg_set_page() using 1GB size for each entry dma_map_sg() I'm able to DMA upto 1GB successfully and validate the data. Also, DMA above 1GB completes w/o any error, but data isn't correct starting immediately after 1GB i.e. second GB offset 0x40000000 starts showing data mismatches. I've used get_user_pages_fast() in two ways to no avail: 1. populate page array w/ first page of 1GB hugepage and used sg_set_page() for setting 1GB size of the page entry. This debugging effort uses the fact that all pages following the first page of huge page start address are contiguous. Ideally dma_map_sg() should coalesce contiguous pages, and my intention was to collect more data from debugging. 2. populate page array w/ all pages from all hugepages Thanks, -am On Sun, Dec 1, 2019 at 7:33 PM Anand Misra <[email protected]> wrote: > [+iommu_list] > > Application isn't aware of hugepage but a userspace (lower) level stack is > aware of the type of memory being allocated on behalf of application, which > in turn communicates w/ driver via ioctl. I'm trying to make it more > agnostic by using dma_map_sg() when multiple GBs are required by > application. Otherwise, I'm using dmap_map_page(). Admittedly, I'm learning > these concepts/APIs for Linux along the way. > > Thanks, > -am > > > On Sun, Dec 1, 2019 at 7:12 PM Lu Baolu <[email protected]> wrote: > >> Hi, >> >> On 12/2/19 11:00 AM, Anand Misra wrote: >> > Thanks, Lu Baolu. This is the dev version we've in our company. I can >> > try on a Ubuntu with a recent kernel version. Although, do you think >> I'm > going in the right direction? Is it possible to have multiple >> hugepages >> > mapped via iommu to get contiguous mapping for DMA? >> > >> >> You mentioned: >> >> " >> I'm trying to use iommu for multiple hugepages (mmap'ed by process and >> pushed to driver via ioctl). The expectation is to have multiple >> hugepages mapped via iommu with each huge page having an entry in iommu >> (i.e. minimize table walk for DMA). Is this possible? >> " >> >> Currently huge page mapping is hidden in iommu driver according to the >> iommu capability and size of map range. Why do you want to be aware of >> it in driver or even application level? >> >> Best regards, >> baolu >> >> > -am >> > >> > >> > On Sun, Dec 1, 2019 at 6:24 PM Lu Baolu <[email protected] >> > <mailto:[email protected]>> wrote: >> > >> > Hi, >> > >> > On 12/2/19 9:46 AM, Anand Misra wrote: >> > > Hello: >> > > >> > > I'm in process of adding iommu support in my driver for a PCIe >> > device. >> > > The device doesn't publish ACS/ATS via its config space. I've >> > following >> > > config: >> > > >> > > Linux cmdline: "intel-iommu=on iommu=pt >> > > vfio_iommu_type1.allow_unsafe_interrupts=1 >> > pcie_acs_override=downstream" >> > > Centos kernel: 3.10.0-1062.1.2.el7.x86_64 >> > > >> > >> > Can you please use the latest kernel for test? 3.10 seems to be >> pretty >> > old and there are a lot of changes after it. >> > >> > Best regards, >> > baolu >> > >> >
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