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

From: Qiang Ma

Date: Thu Oct 30 2025 - 06:46:25 EST


在 2025/10/30 18:36, Ard Biesheuvel 写道:
On Thu, 30 Oct 2025 at 11:25, Qiang Ma <maqianga@xxxxxxxxxxxxx> wrote:

在 2025/10/30 18:02, Ard Biesheuvel 写道:
On Thu, 30 Oct 2025 at 08:37, Qiang Ma <maqianga@xxxxxxxxxxxxx> wrote:
在 2025/10/29 22:15, Ard Biesheuvel 写道:
On Wed, 29 Oct 2025 at 10:55, Qiang Ma <maqianga@xxxxxxxxxxxxx> wrote:
在 2025/10/28 21:42, Ard Biesheuvel 写道:
On Mon, 27 Oct 2025 at 04:46, Qiang Ma <maqianga@xxxxxxxxxxxxx> wrote:
在 2025/10/23 16:30, Ard Biesheuvel 写道:
On Thu, 23 Oct 2025 at 10:22, Qiang Ma <maqianga@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
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?

The current idea is to first remove the unnecessary return print from
arm/arm64,
Please leave the ARM code alone.
I see.
and then remove RISC-V later, as this RISC-V code is also adapted based
on arm64.

RISC-V copied the ARM code and used it as a starting point. That does
not mean it has to remain that way.
I can propose a patch specifically for RISC-V.