linux-kernel - Re: [5.17 regression] "x86/PCI: Ignore E820 reservations for bridge windows on newer systems" breaks suspend/resume

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Date:   Thu, 10 Feb 2022 08:39:48 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Myron Stowe <myron.stowe@...hat.com>,
        Juha-Pekka Heikkila <juhapekka.heikkila@...il.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        linux-acpi <linux-acpi@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>, x86@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Benoit Grégoire <benoitg@...us.ca>,
        Hui Wang <hui.wang@...onical.com>
Subject: Re: [5.17 regression] "x86/PCI: Ignore E820 reservations for bridge
 windows on newer systems" breaks suspend/resume

Hi Hans,

On Wed, Feb 09, 2022 at 05:08:13PM +0100, Hans de Goede wrote:
> As mentioned in my email from 10 seconds ago I think a better simpler
> fix would be to just do:
> 
> diff --git a/arch/x86/kernel/resource.c b/arch/x86/kernel/resource.c
> index 9b9fb7882c20..18656f823764 100644
> --- a/arch/x86/kernel/resource.c
> +++ b/arch/x86/kernel/resource.c
> @@ -28,6 +28,10 @@ static void remove_e820_regions(struct resource *avail)
>  	int i;
>  	struct e820_entry *entry;
>  
> +	/* Only remove E820 reservations on classic BIOS boot */
> +	if (efi_enabled(EFI_MEMMAP))
> +		return;
> +
>  	for (i = 0; i < e820_table->nr_entries; i++) {
>  		entry = &e820_table->entries[i];
>  
> 
> I'm curious what you think of that?

I'm not an expert in this e820 stuff but this one looks really simple
and makes sense to me. So definitely should go with it assuming there
are no objections from the x86 maintainers.