linux-kernel - RE: [PATCH v5 12/16] PCI: Add pci_iomap_host_shared(), pci_iomap_host_shared

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Message-ID: <DM8PR11MB57500B2D821E8AAF93EB66CEE7B89@DM8PR11MB5750.namprd11.prod.outlook.com>
Date:   Thu, 14 Oct 2021 07:27:42 +0000
From:   "Reshetova, Elena" <elena.reshetova@...el.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
CC:     Andi Kleen <ak@...ux.intel.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "Lutomirski, Andy" <luto@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Richard Henderson <rth@...ddle.net>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "James E J Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        "David S . Miller" <davem@...emloft.net>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Paolo Bonzini <pbonzini@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter H Anvin <hpa@...or.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        X86 ML <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        "linux-alpha@...r.kernel.org" <linux-alpha@...r.kernel.org>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Subject: RE: [PATCH v5 12/16] PCI: Add pci_iomap_host_shared(),
 pci_iomap_host_shared_range()

> On Thu, Oct 14, 2021 at 06:32:32AM +0000, Reshetova, Elena wrote:
> > > On Tue, Oct 12, 2021 at 06:36:16PM +0000, Reshetova, Elena wrote:
> > > > > The 5.15 tree has something like ~2.4k IO accesses (including MMIO and
> > > > > others) in init functions that also register drivers (thanks Elena for
> > > > > the number)
> > > >
> > > > To provide more numbers on this. What I can see so far from a smatch-based
> > > > analysis, we have 409 __init style functions (.probe & builtin/module_
> > > > _platform_driver_probe excluded) for 5.15 with allyesconfig.
> > >
> > > I don't think we care about allyesconfig at all though.
> > > Just don't do that.
> > > How about allmodconfig? This is closer to what distros actually do.
> >
> > It does not make any difference really for the content of the /drivers/*:
> > gives 408 __init style functions doing IO (.probe & builtin/module_
> > > > _platform_driver_probe excluded) for 5.15 with allmodconfig:
> >
> > ['doc200x_ident_chip',
> > 'doc_probe', 'doc2001_init', 'mtd_speedtest_init',
> > 'mtd_nandbiterrs_init', 'mtd_oobtest_init', 'mtd_pagetest_init',
> > 'tort_init', 'mtd_subpagetest_init', 'fixup_pmc551',
> > 'doc_set_driver_info', 'init_amd76xrom', 'init_l440gx',
> > 'init_sc520cdp', 'init_ichxrom', 'init_ck804xrom', 'init_esb2rom',
> > 'probe_acpi_namespace_devices', 'amd_iommu_init_pci', 'state_next',
> > 'arm_v7s_do_selftests', 'arm_lpae_run_tests', 'init_iommu_one',
> 
> Um. ARM? Which architecture is this build for?

The list of smatch IO findings is built for x86, but the smatch cross function
database covers all archs, so when queried for all potential function callers,
it would show non x86 arch call chains also. 

Here is the original x86 finding and call chain for the 'arm_v7s_do_selftests':

  Detected low-level IO from arm_v7s_do_selftests in fun
__iommu_queue_command_sync

drivers/iommu/amd/iommu.c:1025 __iommu_queue_command_sync() error:
{15002074744551330002}
    'check_host_input' read from the host using function 'readl' to a
member of the structure 'iommu->cmd_buf_head';

__iommu_queue_command_sync()
  iommu_completion_wait()
    amd_iommu_domain_flush_complete()
      iommu_v1_map_page()
        arm_v7s_do_selftests()

So, the results can be further filtered if you want a specified arch.