Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20211002124012.18186-1-ajaygargnsit@gmail.com>
 <b9afdade-b121-cc9e-ce85-6e4ff3724ed9@linux.intel.com> <CAHP4M8Us753hAeoXL7E-4d29rD9+FzUwAqU6gKNmgd8G0CaQQw@mail.gmail.com>
 <20211004163146.6b34936b.alex.williamson@redhat.com> <CAHP4M8UeGRSqHBV+wDPZ=TMYzio0wYzHPzq2Y+JCY0uzZgBkmA@mail.gmail.com>
 <CAHP4M8UD-k76cg0JmeZAwaWh1deSP82RCE=VC1zHQEYQmX6N9A@mail.gmail.com>
 <CAHP4M8VPem7xEtx3vQPm3bzCQif7JZFiXgiUGZVErTt5vhOF8A@mail.gmail.com> <20211011085247.7f887b12.alex.williamson@redhat.com>
In-Reply-To: <20211011085247.7f887b12.alex.williamson@redhat.com>
From:   Ajay Garg <ajaygargnsit@gmail.com>
Date:   Mon, 11 Oct 2021 23:43:29 +0530
Message-ID: <CAHP4M8UmnBH58H3qqba1p3kyEiPUk9xTp063yJr8RFduUNjgbg@mail.gmail.com>
Subject: Re: [PATCH] iommu: intel: remove flooding of non-error logs, when
 new-DMA-PTE is the same as old-DMA-PTE.
To:     Alex Williamson <alex.williamson@redhat.com>
Cc:     Lu Baolu <baolu.lu@linux.intel.com>,
        "Tian, Kevin" <kevin.tian@intel.com>,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Thanks Alex for your time.

I think I may have found the issue. Right now, when doing a
dma-unmapping, we do a "soft-unmapping" only, as the pte-values
themselves are not cleared in the unlinked pagetable-frame.

I have made the (simple) changes, and things are looking good as of
now (almost an hour now).
However, this time I will give it a day ;)

If there is not a single-flooding observed in the next 24 hours, I
would float the v2 patch for review.


Thanks again for your time and patience.


Thanks and Regards,
Ajay


>
> Even this QEMU explanation doesn't make a lot of sense, vfio tracks
> userspace mappings and will return an -EEXIST error for duplicate or
> overlapping IOVA entries.  We expect to have an entirely empty IOMMU
> domain when a device is assigned, but it seems the only way userspace
> can trigger duplicate PTEs would be if mappings already exist, or we
> have a bug somewhere.
>
> If the most recent instance is purely on bare metal, then it seems the
> host itself has conflicting mappings.  I can only speculate with the
> limited data presented, but I'm suspicious there's something happening
> with RMRRs here (but that should also entirely preclude assignment).
> dmesg, lspci -vvv, and VM configuration would be useful.  Thanks,
>
> Alex
>