Re: [PATCH] iommu/amd: Fix event counter availability check

[Suravee Suthikulpanit]

On 6/16/20 3:48 AM, Alexander Monakov wrote:
> > Alexander
> >
> > On 6/1/20 4:01 PM, Alexander Monakov wrote:
> > > On Mon, 1 Jun 2020, Suravee Suthikulpanit wrote:
> > >
> > > > > Moving init_iommu_perf_ctr just after iommu_flush_all_caches resolves
> > > > > the issue. This is the earliest point in amd_iommu_init_pci where the
> > > > > call succeeds on my laptop.
> > > > According to your description, it should just need to be anywhere after
> > > > the
> > > > pci_enable_device() is called for the IOMMU device, isn't it? So, on your
> > > > system, what if we just move the init_iommu_perf_ctr() here:
> > > No, this doesn't work, as I already said in the paragraph you are responding
> > > to. See my last sentence in the quoted part.
> > >
> > > So the implication is init_device_table_dma together with subsequent cache
> > > flush is also setting up something that is necessary for counters to be
> > > writable.
> > >
> > > Alexander
> > Instead of blindly moving the code around to a spot that would just work,
> > I am trying to understand what might be required here. In this case,
> > the init_device_table_dma()should not be needed. I suspect it's the IOMMU
> > invalidate all command that's also needed here.
> >
> > I'm also checking with the HW and BIOS team. Meanwhile, could you please give
> > the following change a try:
> Hello. Can you give any update please?
>
> Alexander

Sorry for late reply. I have a reproducer and working with the HW team to understand the issue.
I should be able to provide update with solution by the end of this week.

Suravee