linux-kernel - Re: [PATCH 2/5] efi/fake_mem: Arrange for a resource entry per efi_fake

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Date:   Tue, 3 Mar 2020 09:01:09 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] efi/fake_mem: Arrange for a resource entry per
 efi_fake_mem instance

On Mon, 2 Mar 2020 at 23:36, Dan Williams <dan.j.williams@...el.com> wrote:
>
> In preparation for attaching a platform device per iomem resource teach
> the efi_fake_mem code to create an e820 entry per instance. Similar to
> E820_TYPE_PRAM, bypass merging resource when the e820 map is sanitized.
>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: x86@...nel.org
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Acked-by: Ard Biesheuvel <ardb@...nel.org>

> ---
>  arch/x86/kernel/e820.c              |   16 +++++++++++++++-
>  drivers/firmware/efi/x86_fake_mem.c |   12 +++++++++---
>  2 files changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index c5399e80c59c..96babb3a6629 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -305,6 +305,20 @@ static int __init cpcompare(const void *a, const void *b)
>         return (ap->addr != ap->entry->addr) - (bp->addr != bp->entry->addr);
>  }
>
> +static bool e820_nomerge(enum e820_type type)
> +{
> +       /*
> +        * These types may indicate distinct platform ranges aligned to
> +        * numa node, protection domain, performance domain, or other
> +        * boundaries. Do not merge them.
> +        */
> +       if (type == E820_TYPE_PRAM)
> +               return true;
> +       if (type == E820_TYPE_SOFT_RESERVED)
> +               return true;
> +       return false;
> +}
> +
>  int __init e820__update_table(struct e820_table *table)
>  {
>         struct e820_entry *entries = table->entries;
> @@ -380,7 +394,7 @@ int __init e820__update_table(struct e820_table *table)
>                 }
>
>                 /* Continue building up new map based on this information: */
> -               if (current_type != last_type || current_type == E820_TYPE_PRAM) {
> +               if (current_type != last_type || e820_nomerge(current_type)) {
>                         if (last_type != 0)      {
>                                 new_entries[new_nr_entries].size = change_point[chg_idx]->addr - last_addr;
>                                 /* Move forward only if the new size was non-zero: */
> diff --git a/drivers/firmware/efi/x86_fake_mem.c b/drivers/firmware/efi/x86_fake_mem.c
> index e5d6d5a1b240..0bafcc1bb0f6 100644
> --- a/drivers/firmware/efi/x86_fake_mem.c
> +++ b/drivers/firmware/efi/x86_fake_mem.c
> @@ -38,7 +38,7 @@ void __init efi_fake_memmap_early(void)
>                 m_start = mem->range.start;
>                 m_end = mem->range.end;
>                 for_each_efi_memory_desc(md) {
> -                       u64 start, end;
> +                       u64 start, end, size;
>
>                         if (md->type != EFI_CONVENTIONAL_MEMORY)
>                                 continue;
> @@ -58,11 +58,17 @@ void __init efi_fake_memmap_early(void)
>                          */
>                         start = max(start, m_start);
>                         end = min(end, m_end);
> +                       size = end - start + 1;
>
>                         if (end <= start)
>                                 continue;
> -                       e820__range_update(start, end - start + 1, E820_TYPE_RAM,
> -                                       E820_TYPE_SOFT_RESERVED);
> +
> +                       /*
> +                        * Ensure each efi_fake_mem instance results in
> +                        * a unique e820 resource
> +                        */
> +                       e820__range_remove(start, size, E820_TYPE_RAM, 1);
> +                       e820__range_add(start, size, E820_TYPE_SOFT_RESERVED);
>                         e820__update_table(e820_table);
>                 }
>         }
>