(Cc the correct arm mailing list)
On Thu, Feb 15, 2024 at 02:51:06PM -0800, Boqun Feng wrote:
> Currently ACPI_MEMORY_NVS is omitted from the linear map, which causes
> a trouble with the following firmware memory region setup:
>
> [..] efi: 0x0000dfd62000-0x0000dfd83fff [ACPI Reclaim|...]
> [..] efi: 0x0000dfd84000-0x0000dfd87fff [ACPI Mem NVS|...]
>
> , on ARM64 with 64k page size, the whole 0x0000dfd80000-0x0000dfd8ffff
> range will be omitted from the the linear map due to 64k round-up. And
> a page fault happens when trying to access the ACPI_RECLAIM_MEMORY:
>
> [...] Unable to handle kernel paging request at virtual address ffff0000dfd80000
>
> To fix this, add ACPI_MEMORY_NVS into the linear map.
>
> Signed-off-by: Boqun Feng <[email protected]>
> Cc: [email protected] # 5.15+
> ---
> We hit this in an ARM64 Hyper-V VM when using 64k page size, although
> this issue may also be fixed if the efi memory regions are all 64k
> aligned, but I don't find this memory region setup is invalid per UEFI
> spec, also I don't find that spec disallows ACPI_MEMORY_NVS to be mapped
> in the OS linear map, but if there is any better way or I'm reading the
> spec incorrectly, please let me know.
>
> It's Cced stable since 5.15 because that's when Hyper-V ARM64 support is
> added, and Hyper-V is the only one that hits the problem so far.
>
> drivers/firmware/efi/efi-init.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/firmware/efi/efi-init.c b/drivers/firmware/efi/efi-init.c
> index a00e07b853f2..9a1b9bc66d50 100644
> --- a/drivers/firmware/efi/efi-init.c
> +++ b/drivers/firmware/efi/efi-init.c
> @@ -139,6 +139,7 @@ static __init int is_usable_memory(efi_memory_desc_t *md)
> case EFI_LOADER_CODE:
> case EFI_LOADER_DATA:
> case EFI_ACPI_RECLAIM_MEMORY:
> + case EFI_ACPI_MEMORY_NVS:
> case EFI_BOOT_SERVICES_CODE:
> case EFI_BOOT_SERVICES_DATA:
> case EFI_CONVENTIONAL_MEMORY:
> @@ -202,8 +203,12 @@ static __init void reserve_regions(void)
> if (!is_usable_memory(md))
> memblock_mark_nomap(paddr, size);
>
> - /* keep ACPI reclaim memory intact for kexec etc. */
> - if (md->type == EFI_ACPI_RECLAIM_MEMORY)
> + /*
> + * keep ACPI reclaim and NVS memory and intact for kexec
> + * etc.
> + */
> + if (md->type == EFI_ACPI_RECLAIM_MEMORY ||
> + md->type == EFI_ACPI_MEMORY_NVS)
> memblock_reserve(paddr, size);
> }
> }
> --
> 2.43.0
>