On Thu, 12 Sep 2019 07:02:56 PDT (-0700), will@xxxxxxxxxx wrote:
On Sun, Sep 08, 2019 at 07:52:55AM +0800, Guo Ren wrote:
On Mon, Jun 24, 2019 at 6:40 PM Will Deacon <will@xxxxxxxxxx> wrote:
> > I'll keep my system use the same ASID for SMP + IOMMU :P
>
> You will want a separate allocator for that:
>
> https://lkml.kernel.org/r/20190610184714.6786-2-jean-philippe.brucker@xxxxxxx
Yes, it is hard to maintain ASID between IOMMU and CPUMMU or different
system, because it's difficult to synchronize the IO_ASID when the CPU
ASID is rollover.
But we could still use hardware broadcast TLB invalidation instruction
to uniformly manage the ASID and IO_ASID, or OTHER_ASID in our IOMMU.
That's probably a bad idea, because you'll likely stall execution on the
CPU until the IOTLB has completed invalidation. In the case of ATS, I think
an endpoint ATC is permitted to take over a minute to respond. In reality, I
suspect the worst you'll ever see would be in the msec range, but that's
still an unacceptable period of time to hold a CPU.
Welcome to join our disscusion:
"Introduce an implementation of IOMMU in linux-riscv"
9 Sep 2019, 10:45 Jade-room-I&II (Corinthia Hotel Lisbon) RISC-V MC
I attended this session, but it unfortunately raised many more questions
than it answered.
Ya, we're a long way from figuring this out.
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