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

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Message-ID: <alpine.LNX.2.20.13.2006302219240.6255@monopod.intra.ispras.ru>
Date:   Tue, 30 Jun 2020 22:22:55 +0300 (MSK)
From:   Alexander Monakov <amonakov@...ras.ru>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>
cc:     linux-kernel@...r.kernel.org, Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org
Subject: Re: [PATCH] iommu/amd: Fix event counter availability check

On Tue, 16 Jun 2020, Suravee Suthikulpanit wrote:

> > > 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.

Hi, can you share any information (two more weeks have passed)?

Alexander