Re: [PATCH Part1 RFC v4 24/36] x86/compressed/acpi: move EFI config table access to common code

Borislav Petkov
2021-08-19T10:47:28Z

On Wed, Jul 07, 2021 at 01:14:54PM -0500, Brijesh Singh wrote:
> From: Michael Roth <michael.roth@amd.com>
>
> Future patches for SEV-SNP-validated CPUID will also require early
> parsing of the EFI configuration. Move the related code into a set of
> helpers that can be re-used for that purpose.
>
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
> arch/x86/boot/compressed/Makefile | 1 +
> arch/x86/boot/compressed/acpi.c | 124 +++++---------
> arch/x86/boot/compressed/efi-config-table.c | 180 ++++++++++++++++++++
> arch/x86/boot/compressed/misc.h | 50 ++++++
> 4 files changed, 272 insertions(+), 83 deletions(-)
> create mode 100644 arch/x86/boot/compressed/efi-config-table.c

arch/x86/boot/compressed/efi.c

should be good enough.

And in general, this patch is hard to review because it does a bunch of
things at the same time. You should split it:

- the first patch sould carve out only the functionality into helpers
without adding or changing the existing functionality.

- later ones should add the new functionality, in single logical steps.

Some preliminary comments below as far as I can:

> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 431bf7f846c3..b41aecfda49c 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -100,6 +100,7 @@ endif
> vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
>
> vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o
> +vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi-config-table.o
> efi-obj-$(CONFIG_EFI_STUB) = $(objtree)/drivers/firmware/efi/libstub/lib.a
>
> $(obj)/vmlinux: $(vmlinux-objs-y) $(efi-obj-y) FORCE
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> index 8bcbcee54aa1..e087dcaf43b3 100644
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -24,42 +24,36 @@ struct mem_vector immovable_mem[MAX_NUMNODES*2];
> * Search EFI system tables for RSDP. If both ACPI_20_TABLE_GUID and
> * ACPI_TABLE_GUID are found, take the former, which has more features.
> */
> +#ifdef CONFIG_EFI
> +static bool
> +rsdp_find_fn(efi_guid_t guid, unsigned long vendor_table, bool efi_64,
> + void *opaque)
> +{
> + acpi_physical_address *rsdp_addr = opaque;
> +
> + if (!(efi_guidcmp(guid, ACPI_TABLE_GUID))) {
> + *rsdp_addr = vendor_table;
> + } else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID))) {
> + *rsdp_addr = vendor_table;
> + return false;

No "return false" in the ACPI_TABLE_GUID branch above? Maybe this has to
do with the preference to ACPI_20_TABLE_GUID.

In any case, this looks silly. Please do the iteration simple
and stupid without the function pointer and get rid of that
efi_foreach_conf_entry() thing - this is not firmware.

> diff --git a/arch/x86/boot/compressed/efi-config-table.c b/arch/x86/boot/compressed/efi-config-table.c
> new file mode 100644
> index 000000000000..d1a34aa7cefd
> --- /dev/null
> +++ b/arch/x86/boot/compressed/efi-config-table.c

...

> +/*

If you're going to add proper comments, make them kernel-doc. I.e., it
should start with

/**

and then use

./scripts/kernel-doc -none arch/x86/boot/compressed/efi-config-table.c

to check them all they're proper.

> + * Given boot_params, retrieve the physical address of EFI system table.
> + *
> + * @boot_params: pointer to boot_params
> + * @sys_table_pa: location to store physical address of system table
> + * @is_efi_64: location to store whether using 64-bit EFI or not
> + *
> + * Returns 0 on success. On error, return params are left unchanged.
> + */
> +int
> +efi_bp_get_system_table(struct boot_params *boot_params,

There's no need for the "_bp_" - just efi_get_system_table(). Ditto for
the other naming.

I'll review the rest properly after you've split it.

Thx.

--
Regards/Gruss,
Boris.