linux-kernel - Re: [PATCH 1/2] efi: Add efi_memmap

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Date:   Wed, 25 Sep 2019 17:29:08 +0200
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Yunfeng Ye <yeyunfeng@...wei.com>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        "tglx@...utronix.de" <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>,
        linux-efi <linux-efi@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] efi: Add efi_memmap_free() to free EFI memory map

On Wed, 25 Sep 2019 at 11:17, Yunfeng Ye <yeyunfeng@...wei.com> wrote:
>
> In efi_fake_memmap(), the commit 20b1e22d01a4 ("x86/efi: Don't allocate
> memmap through memblock after mm_init()") replace memblock_alloc() with
> efi_memmap_alloc(), but there is no matching modification of
> memblock_free() when early_memremap() fail.
>
> Fix this by adding efi_memmap_free() to instead of memblock_free().
>
> Fixes: 20b1e22d01a4 ("x86/efi: Don't allocate memmap through memblock after mm_init()")
> Signed-off-by: Yunfeng Ye <yeyunfeng@...wei.com>

What happens if you try to call efi_memmap_free() /after/ slab has
become available on an allocation that was created before?

> ---
>  drivers/firmware/efi/fake_mem.c |  2 +-
>  drivers/firmware/efi/memmap.c   | 34 ++++++++++++++++++++++++++++++++++
>  include/linux/efi.h             |  1 +
>  3 files changed, 36 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/fake_mem.c b/drivers/firmware/efi/fake_mem.c
> index 9501edc..c2f69f6 100644
> --- a/drivers/firmware/efi/fake_mem.c
> +++ b/drivers/firmware/efi/fake_mem.c
> @@ -65,7 +65,7 @@ void __init efi_fake_memmap(void)
>         new_memmap = early_memremap(new_memmap_phy,
>                                     efi.memmap.desc_size * new_nr_map);
>         if (!new_memmap) {
> -               memblock_free(new_memmap_phy, efi.memmap.desc_size * new_nr_map);
> +               efi_memmap_free(new_memmap_phy, new_nr_map);
>                 return;
>         }
>
> diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
> index 38b686c..35dc189 100644
> --- a/drivers/firmware/efi/memmap.c
> +++ b/drivers/firmware/efi/memmap.c
> @@ -18,6 +18,11 @@ static phys_addr_t __init __efi_memmap_alloc_early(unsigned long size)
>         return memblock_phys_alloc(size, SMP_CACHE_BYTES);
>  }
>
> +static void __init __efi_memmap_free_early(phys_addr_t addr, unsigned long size)
> +{
> +       memblock_free(addr, size);
> +}
> +
>  static phys_addr_t __init __efi_memmap_alloc_late(unsigned long size)
>  {
>         unsigned int order = get_order(size);
> @@ -29,6 +34,15 @@ static phys_addr_t __init __efi_memmap_alloc_late(unsigned long size)
>         return PFN_PHYS(page_to_pfn(p));
>  }
>
> +static void __init __efi_memmap_free_late(phys_addr_t addr, unsigned long size)
> +{
> +       unsigned int order = get_order(size);
> +       struct page *p = pfn_to_page(PHYS_PFN(addr));
> +
> +       if (p)
> +               __free_pages(p, order);
> +}
> +
>  /**
>   * efi_memmap_alloc - Allocate memory for the EFI memory map
>   * @num_entries: Number of entries in the allocated map.
> @@ -50,6 +64,26 @@ phys_addr_t __init efi_memmap_alloc(unsigned int num_entries)
>  }
>
>  /**
> + * efi_memmap_free - Free memory for the EFI memory map
> + * @addr: Physical address of the EFI memory map to be freed.
> + * @num_entries: Number of the EFI memory map entries.
> + *
> + * Depending on whether mm_init() has already been invoked or not,
> + * either memblock or "normal" page free is used.
> + */
> +void __init efi_memmap_free(phys_addr_t addr, unsigned int num_entries)
> +{
> +       unsigned long size = num_entries * efi.memmap.desc_size;
> +
> +       if (slab_is_available()) {
> +               __efi_memmap_free_late(addr, size);
> +
> +               return;
> +       }
> +       __efi_memmap_free_early(addr, size);
> +}
> +
> +/**
>   * __efi_memmap_init - Common code for mapping the EFI memory map
>   * @data: EFI memory map data
>   * @late: Use early or late mapping function?
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index bd38370..8bb741a 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -1057,6 +1057,7 @@ static inline efi_status_t efi_query_variable_store(u32 attributes,
>  extern void __iomem *efi_lookup_mapped_addr(u64 phys_addr);
>
>  extern phys_addr_t __init efi_memmap_alloc(unsigned int num_entries);
> +extern void __init efi_memmap_free(phys_addr_t addr, unsigned int num_entries);
>  extern int __init efi_memmap_init_early(struct efi_memory_map_data *data);
>  extern int __init efi_memmap_init_late(phys_addr_t addr, unsigned long size);
>  extern void __init efi_memmap_unmap(void);
> --
> 1.8.3.1
>