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

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Date:   Thu, 14 Oct 2021 05:26:20 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     "Reshetova, Elena" <elena.reshetova@...el.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 07:27:42AM +0000, Reshetova, Elena wrote:
> > 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. 

So what is it just for x86? Could you tell?

-- 
MST