linux-kernel - Re: [PATCH] efi: memmap insertion should adjust the vaddr as well

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Date:   Sun, 7 Mar 2021 18:24:58 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Kairui Song <kasong@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH] efi: memmap insertion should adjust the vaddr as well

On Wed, 24 Feb 2021 at 19:43, Kairui Song <kasong@...hat.com> wrote:
>
> Currently when efi_memmap_insert is called, only the
> physical memory addresses are re-calculated. The virt
> addresses of the split entries are untouched.
>
> If any later operation depends on the virt_addaress info, things
> will go wrong. One case it may fail is kexec on x86, after kexec,
> efi is already in virtual mode, kernel simply do fixed mapping
> reuse the recorded virt address. If the virt address is incorrect,
> the mapping will be invalid.
>
> Update the virt_addaress as well when inserting a memmap entry to
> fix this potential issue.
>
> Signed-off-by: Kairui Song <kasong@...hat.com>
> ---
>  drivers/firmware/efi/memmap.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
> index 2ff1883dc788..de5c545b2074 100644
> --- a/drivers/firmware/efi/memmap.c
> +++ b/drivers/firmware/efi/memmap.c
> @@ -292,7 +292,7 @@ void __init efi_memmap_insert(struct efi_memory_map *old_memmap, void *buf,
>  {
>         u64 m_start, m_end, m_attr;
>         efi_memory_desc_t *md;
> -       u64 start, end;
> +       u64 start, end, virt_offset;
>         void *old, *new;
>
>         /* modifying range */
> @@ -321,6 +321,11 @@ void __init efi_memmap_insert(struct efi_memory_map *old_memmap, void *buf,
>                 start = md->phys_addr;
>                 end = md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT) - 1;
>
> +               if (md->virt_addr)
> +                       virt_offset = md->virt_addr - md->phys_addr;
> +               else
> +                       virt_offset = -1;
> +

Should we take EFI_MEMORY_RUNTIME into account here? I don't think we
should expect to see non-zero virtual addresses if that attribute is
missing.


>                 if (m_start <= start && end <= m_end)
>                         md->attribute |= m_attr;
>
> @@ -337,6 +342,8 @@ void __init efi_memmap_insert(struct efi_memory_map *old_memmap, void *buf,
>                         md->phys_addr = m_end + 1;
>                         md->num_pages = (end - md->phys_addr + 1) >>
>                                 EFI_PAGE_SHIFT;
> +                       if (virt_offset != -1)
> +                               md->virt_addr = md->phys_addr + virt_offset;
>                 }
>
>                 if ((start < m_start && m_start < end) && m_end < end) {
> @@ -351,6 +358,8 @@ void __init efi_memmap_insert(struct efi_memory_map *old_memmap, void *buf,
>                         md->phys_addr = m_start;
>                         md->num_pages = (m_end - m_start + 1) >>
>                                 EFI_PAGE_SHIFT;
> +                       if (virt_offset != -1)
> +                               md->virt_addr = md->phys_addr + virt_offset;
>                         /* last part */
>                         new += old_memmap->desc_size;
>                         memcpy(new, old, old_memmap->desc_size);
> @@ -358,6 +367,8 @@ void __init efi_memmap_insert(struct efi_memory_map *old_memmap, void *buf,
>                         md->phys_addr = m_end + 1;
>                         md->num_pages = (end - m_end) >>
>                                 EFI_PAGE_SHIFT;
> +                       if (virt_offset != -1)
> +                               md->virt_addr = md->phys_addr + virt_offset;
>                 }
>
>                 if ((start < m_start && m_start < end) &&
> @@ -373,6 +384,8 @@ void __init efi_memmap_insert(struct efi_memory_map *old_memmap, void *buf,
>                         md->num_pages = (end - md->phys_addr + 1) >>
>                                 EFI_PAGE_SHIFT;
>                         md->attribute |= m_attr;
> +                       if (virt_offset != -1)
> +                               md->virt_addr = md->phys_addr + virt_offset;
>                 }
>         }
>  }
> --
> 2.29.2
>