linux-kernel - Re: [PATCH v2 2/3] x86: Log resource clipping for E820 regions

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Date:   Fri, 15 Apr 2022 16:12:17 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Myron Stowe <myron.stowe@...hat.com>,
        Juha-Pekka Heikkila <juhapekka.heikkila@...il.com>,
        Benoit Grégoire <benoitg@...us.ca>,
        Hui Wang <hui.wang@...onical.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v2 2/3] x86: Log resource clipping for E820 regions

On Thu, Apr 14, 2022 at 8:23 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> From: Bjorn Helgaas <bhelgaas@...gle.com>
>
> When remove_e820_regions() clips a resource because an E820 region overlaps
> it, log a note in dmesg to add in debugging.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
>  arch/x86/kernel/resource.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kernel/resource.c b/arch/x86/kernel/resource.c
> index 8ffe68437744..30d524adb012 100644
> --- a/arch/x86/kernel/resource.c
> +++ b/arch/x86/kernel/resource.c
> @@ -1,5 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0
>  #include <linux/ioport.h>
> +#include <linux/printk.h>
>  #include <asm/e820/api.h>
>
>  static void resource_clip(struct resource *res, resource_size_t start,
> @@ -28,6 +29,7 @@ static void remove_e820_regions(struct resource *avail)
>         int i;
>         struct e820_entry *entry;
>         u64 e820_start, e820_end;
> +       struct resource orig = *avail;
>
>         for (i = 0; i < e820_table->nr_entries; i++) {
>                 entry = &e820_table->entries[i];
> @@ -35,6 +37,11 @@ static void remove_e820_regions(struct resource *avail)
>                 e820_end = entry->addr + entry->size - 1;
>
>                 resource_clip(avail, e820_start, e820_end);
> +               if (orig.start != avail->start || orig.end != avail->end) {
> +                       pr_info("clipped %pR to %pR for e820 entry [mem %#010Lx-%#010Lx]\n",
> +                                &orig, avail, e820_start, e820_end);
> +                       orig = *avail;
> +               }
>         }
>  }
>
> --
> 2.25.1
>