[PATCH] smbios: arm64: Allow table to be written at a fixed addr

[Caleb Connolly]

Hi Simon,

On 21/10/2023 01:45, Simon Glass wrote:
> U-Boot typically sets up its malloc() pool near the top of memory. On
> ARM64 systems this can result in an SMBIOS table above 4GB which is
> not supported by SMBIOSv2.
> 
> Work around this problem by providing a new option to choose an address
> just below 4GB, if needed.
I may well be missing something here, but I don't quite understand the 
justification behind the original patch [1] which caused this regression.

I'm currently preparing support for a few different Qualcomm boards 
which have different memory layouts, so far it's been possible to avoid 
having any fixed addresses, so the same u-boot image can be used on all 
of them (with just a different DTB).

As I mentioned before, efi_allocate_pages() seems to work fine from 
install_smbios_table(), I haven't delved into the code too much but I 
wonder if this could be an acceptable solution?

Barring that, could we use an environment variable to pass this address 
in? Although I think that might not be a very desirable solution.

I appreciate you taking the time to prepare this patch and CC me. If 
nobody else objects to this patch then I'd prefer to avoid blocking it. 
In either case, I'd greatly appreciate any input on the above 
suggestions so that I can implement a solution for my boards.

Thanks and regards,

[1]: 
https://lore.kernel.org/u-boot/20230920030027.1385833-16-sjg@chromium.org/
> 
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
> 
>   lib/Kconfig                 | 17 +++++++++++++++++
>   lib/efi_loader/efi_smbios.c | 12 ++++++++++++
>   2 files changed, 29 insertions(+)
> 
> diff --git a/lib/Kconfig b/lib/Kconfig
> index f6ca559897e7..a77f2f3e9089 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -994,6 +994,23 @@ config GENERATE_SMBIOS_TABLE
>   	  See also SMBIOS_SYSINFO which allows SMBIOS values to be provided in
>   	  the devicetree.
>   
> +config SMBIOS_TABLE_FIXED
> +	bool "Place the SMBIOS table at a special address"
> +	depends on GENERATE_SMBIOS_TABLE && ARM64 && SMBIOS && EFI_LOADER
> +	default y
> +	help
> +	  Use this option to place the SMBIOS table at a fixed address.
> +
> +	  U-Boot typically sets up its malloc() pool near the top of memory. On
> +	  ARM64 systems this can result in an SMBIOS table above 4GB which is
> +	  not supported by SMBIOSv2. This option works around this problem by
> +	  chosing an address just below 4GB, if needed.
> +
> +config SMBIOS_TABLE_FIXED_ADDR
> +	hex "Fixed address for use for SMBIOS table"
> +	depends on SMBIOS_TABLE_FIXED
> +	default 0xffff0000
> +
>   endmenu
>   
>   config LIB_RATIONAL
> diff --git a/lib/efi_loader/efi_smbios.c b/lib/efi_loader/efi_smbios.c
> index 48446f654d9b..84ea027ea48c 100644
> --- a/lib/efi_loader/efi_smbios.c
> +++ b/lib/efi_loader/efi_smbios.c
> @@ -61,6 +61,18 @@ static int install_smbios_table(void)
>   		return log_msg_ret("mem", -ENOMEM);
>   
>   	addr = map_to_sysmem(buf);
> +
> +	/*
> +	 * Deal with a fixed address if needed. For simplicity we assume that
> +	 * the SMBIOS-table size is <64KB and that the malloc region does not
> +	 * straddle the 4GB boundary.
> +	 */
> +	if (IS_ENABLED(CONFIG_SMBIOS_TABLE_FIXED) && addr >= SZ_4G - SZ_64K) {
> +		addr = IF_ENABLED_INT(CONFIG_SMBIOS_TABLE_FIXED,
> +				      CONFIG_SMBIOS_TABLE_FIXED_ADDR);
> +		log_warning("Forcing SMBIOS table to address %lx\n", addr);
> +	}
> +
>   	if (!write_smbios_table(addr)) {
>   		log_err("Failed to write SMBIOS table\n");
>   		return log_msg_ret("smbios", -EINVAL);

-- 
// Caleb (they/them)