linux-kernel - Re: [PATCH v1 1/1] x86/PCI: Disable e820 usage for the resource allocation

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Date:   Mon, 13 Jun 2022 17:35:20 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Ferry Toth <ftoth@...londelft.nl>
Subject: Re: [PATCH v1 1/1] x86/PCI: Disable e820 usage for the resource
 allocation

On Mon, Jun 13, 2022 at 11:16:41PM +0300, Andy Shevchenko wrote:
> The resource management improve for PCI on x86 broke booting of Intel MID
> platforms. It seems that the current code removes all available resources
> from the list and none of the PCI device may be initialized. Restore the
> old behaviour by force disabling the e820 usage for the resource allocation.
> 
> Fixes: 4c5e242d3e93 ("x86/PCI: Clip only host bridge windows for E820 regions")
> Depends-on: fa6dae5d8208 ("x86/PCI: Add kernel cmdline options to use/ignore E820 reserved regions")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Yeah, I blew it with 4c5e242d3e93.  Can you provide more details on
how the MID platforms broke?  Since you set "pci_use_e820 = false" for
MID below, I assume MID doesn't depend on the e820 clipping and thus
should not break if we turn off clipping by default in 2023 as in
0ae084d5a674 ("x86/PCI: Disable E820 reserved region clipping starting
in 2023").  But it'd be nice to see the dmesg log and make sure.

> ---
>  arch/x86/include/asm/pci_x86.h | 1 +
>  arch/x86/pci/acpi.c            | 2 +-
>  arch/x86/pci/intel_mid_pci.c   | 1 +
>  3 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/pci_x86.h b/arch/x86/include/asm/pci_x86.h
> index f52a886d35cf..503f83fbc686 100644
> --- a/arch/x86/include/asm/pci_x86.h
> +++ b/arch/x86/include/asm/pci_x86.h
> @@ -126,6 +126,7 @@ extern const struct pci_raw_ops *raw_pci_ext_ops;
>  extern const struct pci_raw_ops pci_mmcfg;
>  extern const struct pci_raw_ops pci_direct_conf1;
>  extern bool port_cf9_safe;
> +extern bool pci_use_e820;
>  
>  /* arch_initcall level */
>  #ifdef CONFIG_PCI_DIRECT
> diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> index a4f43054bc79..ac2f220d50fc 100644
> --- a/arch/x86/pci/acpi.c
> +++ b/arch/x86/pci/acpi.c
> @@ -20,7 +20,7 @@ struct pci_root_info {
>  #endif
>  };
>  
> -static bool pci_use_e820 = true;
> +bool pci_use_e820 = true;
>  static bool pci_use_crs = true;
>  static bool pci_ignore_seg;
>  
> diff --git a/arch/x86/pci/intel_mid_pci.c b/arch/x86/pci/intel_mid_pci.c
> index 8edd62206604..7869b86bff04 100644
> --- a/arch/x86/pci/intel_mid_pci.c
> +++ b/arch/x86/pci/intel_mid_pci.c
> @@ -313,6 +313,7 @@ int __init intel_mid_pci_init(void)
>  	pcibios_enable_irq = intel_mid_pci_irq_enable;
>  	pcibios_disable_irq = intel_mid_pci_irq_disable;
>  	pci_root_ops = intel_mid_pci_ops;
> +	pci_use_e820 = false;
>  	pci_soc_mode = 1;
>  	/* Continue with standard init */
>  	acpi_noirq_set();
> -- 
> 2.35.1
>