[bugzilla-daemon@kernel.org: [Bug 219619] New: vfio-pci: screen graphics artifacts after 6.12 kernel upgrade]

[Bjorn Helgaas <helgaas@kernel.org>]

Forwarding since not everybody follows bugzilla.  Apparently bisected
to f9e54c3a2f5b ("vfio/pci: implement huge_fault support").

Athul, f9e54c3a2f5b appears to revert cleanly from v6.13-rc1.  Can you
verify that reverting it is enough to avoid these artifacts?

#regzbot introduced: f9e54c3a2f5b ("vfio/pci: implement huge_fault support")

----- Forwarded message from bugzilla-daemon@kernel.org -----

Date: Sat, 21 Dec 2024 10:10:02 +0000
From: bugzilla-daemon@kernel.org
To: bjorn@helgaf9e54c3a2f5bas.com
Subject: [Bug 219619] New: vfio-pci: screen graphics artifacts after 6.12 kernel upgrade
Message-ID: <bug-219619-41252@https.bugzilla.kernel.org/>

https://bugzilla.kernel.org/show_bug.cgi?id=219619

            Bug ID: 219619
           Summary: vfio-pci: screen graphics artifacts after 6.12 kernel
                    upgrade
           Product: Drivers
           Version: 2.5
          Hardware: AMD
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: PCI
          Assignee: drivers_pci@kernel-bugs.osdl.org
          Reporter: athul.krishna.kr@protonmail.com
        Regression: No

Created attachment 307382
  --> https://bugzilla.kernel.org/attachment.cgi?id=307382&action=edit
dmesg

Device: Asus Zephyrus GA402RJ
CPU: Ryzen 7 6800HS
GPU: RX 6700S
Kernel: 6.13.0-rc3-g8faabc041a00

Problem:
Launching games or gpu bench-marking tools in qemu windows 11 vm will cause
screen artifacts, ultimately qemu will pause with unrecoverable error.

Commit:
f9e54c3a2f5b79ecc57c7bc7d0d3521e461a2101 is the first bad commit
commit f9e54c3a2f5b79ecc57c7bc7d0d3521e461a2101
Author: Alex Williamson <alex.williamson@redhat.com>
Date:   Mon Aug 26 16:43:53 2024 -0400

    vfio/pci: implement huge_fault support

    With the addition of pfnmap support in vmf_insert_pfn_{pmd,pud}() we can
    take advantage of PMD and PUD faults to PCI BAR mmaps and create more
    efficient mappings.  PCI BARs are always a power of two and will typically
    get at least PMD alignment without userspace even trying.  Userspace
    alignment for PUD mappings is also not too difficult.

    Consolidate faults through a single handler with a new wrapper for
    standard single page faults.  The pre-faulting behavior of commit
    d71a989cf5d9 ("vfio/pci: Insert full vma on mmap'd MMIO fault") is removed
    in this refactoring since huge_fault will cover the bulk of the faults and
    results in more efficient page table usage.  We also want to avoid that
    pre-faulted single page mappings preempt huge page mappings.

    Link: https://lkml.kernel.org/r/20240826204353.2228736-20-peterx@redhat.com
    Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
    Signed-off-by: Peter Xu <peterx@redhat.com>
    Cc: Alexander Gordeev <agordeev@linux.ibm.com>
    Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: David Hildenbrand <david@redhat.com>
    Cc: Gavin Shan <gshan@redhat.com>
    Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
    Cc: Heiko Carstens <hca@linux.ibm.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Jason Gunthorpe <jgg@nvidia.com>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Niklas Schnelle <schnelle@linux.ibm.com>
    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Cc: Ryan Roberts <ryan.roberts@arm.com>
    Cc: Sean Christopherson <seanjc@google.com>
    Cc: Sven Schnelle <svens@linux.ibm.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vasily Gorbik <gor@linux.ibm.com>
    Cc: Will Deacon <will@kernel.org>
    Cc: Zi Yan <ziy@nvidia.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

 drivers/vfio/pci/vfio_pci_core.c | 60 ++++++++++++++++++++++++++++------------
 1 file changed, 43 insertions(+), 17 deletions(-)

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