linux-kernel - Re: [PATCH 1/2] ARM/efi: Remove duplicate permission settings

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Message-ID: <CAMj1kXFUUCoE=gZ0kTMKx87qnJMU9J9skT75STTKjjakXb8kmw@mail.gmail.com>
Date: Thu, 30 Oct 2025 11:02:34 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Qiang Ma <maqianga@...ontech.com>
Cc: linux@...linux.org.uk, linux-efi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] ARM/efi: Remove duplicate permission settings

On Thu, 30 Oct 2025 at 08:37, Qiang Ma <maqianga@...ontech.com> wrote:
>
>
> 在 2025/10/29 22:15, Ard Biesheuvel 写道:
> > On Wed, 29 Oct 2025 at 10:55, Qiang Ma <maqianga@...ontech.com> wrote:
> >>
> >> 在 2025/10/28 21:42, Ard Biesheuvel 写道:
> >>> On Mon, 27 Oct 2025 at 04:46, Qiang Ma <maqianga@...ontech.com> wrote:
> >>>> 在 2025/10/23 16:30, Ard Biesheuvel 写道:
> >>>>> On Thu, 23 Oct 2025 at 10:22, Qiang Ma <maqianga@...ontech.com> wrote:
> >>>>>> In the efi_virtmap_init(), permission settings have been applied:
> >>>>>>
> >>>>>> static bool __init efi_virtmap_init(void)
> >>>>>> {
> >>>>>>            ...
> >>>>>>            for_each_efi_memory_desc(md)
> >>>>>>                    ...
> >>>>>>                    efi_create_mapping(&efi_mm, md);
> >>>>>>            ...
> >>>>>>            efi_memattr_apply_permissions(&efi_mm, efi_set_mapping_permissions);
> >>>>>>            ...
> >>>>>> }
> >>>>>>
> >>>>>> Therefore, there is no need to apply it again in the efi_create_mapping().
> >>>>>>
> >>>>>> Fixes: 9fc68b717c24 ("ARM/efi: Apply strict permissions for UEFI Runtime Services regions")
> >>>>>>
> >>>>>> Signed-off-by: Qiang Ma <maqianga@...ontech.com>
> >>>>> No, efi_memattr_apply_permissions() uses the /optional/ memory
> >>>>> attributes table, whereas efi_create_mapping() uses the permission
> >>>>> attributes in the EFI memory map. The memory attributes table is
> >>>>> optional, in which case any RO/XP attributes from the memory map
> >>>>> should be used.
> >>>>>
> >>>> I see.
> >>>>
> >>>> Then, can it be modified like this?
> >>> No
> >>>
> >>>> --- a/arch/arm/kernel/efi.c
> >>>> +++ b/arch/arm/kernel/efi.c
> >>>> @@ -65,16 +65,13 @@ int __init efi_create_mapping(struct mm_struct *mm,
> >>>> efi_memory_desc_t *md)
> >>>>                    desc.type = MT_MEMORY_RWX_NONCACHED;
> >>>>            else if (md->attribute & EFI_MEMORY_WC)
> >>>>                    desc.type = MT_DEVICE_WC;
> >>>> +       else if (md->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))
> >>> This will be true for RO, XP or RO+XP.
> >>>
> >>>> +               desc.type = MT_MEMORY_RO;
> >>> This will apply RO permissions even to XP regions, which need to be writable.
> >>>
> >> Thanks for your review.
> >> I see.
> >>
> >> I can introduce a new type MT_MEMORY_RO_XP, to describe RO+XP,
> >> and then we can use the RO+XP attribute to implement memory mapping.
> >>
> > Why? The current code is working fine, no?
> >
> Yes, the current code is running normally.
>
> The reasons for the modification are as follows:
> I noticed that the arm64/RISC-V efi_create_mapping() always return 0,
> but in the code where efi_virtmap_init() calls it, it is as follows:
>
> ret = efi_create_mapping(&efi_mm, md);
> if (ret) {
>      pr_warn("  EFI remap %pa: failed to create mapping (%d)\n",
>          &phys, ret);
>      return false;
> }
>
> This return error print is unnecessary, so I want to remove it.

So what is preventing you from removing this from the RISC-V version?