[PATCH v2 3/6] smbios: Use SMBIOS 3.0 to support an address above 4GB

[Ilias Apalodimas]

Hi Simon

On Tue, 21 Nov 2023 at 04:17, Simon Glass <sjg at chromium.org> wrote:
>
> Hi Heinrich,
>
> On Mon, 20 Nov 2023 at 19:11, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> >
> > On 10/15/23 04:45, Simon Glass wrote:
> > > When the SMBIOS table is written to an address above 4GB a 32-bit table
> > > address is not large enough.
> > >
> > > Use an SMBIOS3 table in that case.
> > >
> > > Note that we cannot use efi_allocate_pages() since this function has
> > > nothing to do with EFI. There is no equivalent function to allocate
> > > memory below 4GB in U-Boot. One solution would be to create a separate
> > > malloc() pool, or just always put the malloc() pool below 4GB.
> > >
> > > Signed-off-by: Simon Glass <sjg at chromium.org>
> > > ---
> > >
> > > Changes in v2:
> > > - Check the end of the table rather than the start.
> > >
> > >   include/smbios.h | 22 +++++++++++++++++++++-
> > >   lib/smbios.c     | 24 +++++++++++++++++++-----
> > >   2 files changed, 40 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/include/smbios.h b/include/smbios.h
> > > index c9df2706f5a6..ddabb558299e 100644
> > > --- a/include/smbios.h
> > > +++ b/include/smbios.h
> > > @@ -12,7 +12,8 @@
> > >
> > >   /* SMBIOS spec version implemented */
> > >   #define SMBIOS_MAJOR_VER    3
> > > -#define SMBIOS_MINOR_VER     0
> > > +#define SMBIOS_MINOR_VER     7
> > > +
> > >
> > >   enum {
> > >       SMBIOS_STR_MAX  = 64,   /* Maximum length allowed for a string */
> > > @@ -54,6 +55,25 @@ struct __packed smbios_entry {
> > >       u8 bcd_rev;
> > >   };
> > >
> > > +struct __packed smbios3_entry {
> > > +     u8 anchor[5];
> > > +     u8 checksum;
> > > +     u8 length;
> > > +     u8 major_ver;
> > > +
> > > +     u8 minor_ver;
> > > +     u8 docrev;
> > > +     u8 entry_point_rev;
> > > +     u8 reserved;
> > > +     u32 max_struct_size;
> > > +
> > > +     u64 struct_table_address;
> > > +};
> > > +
> > > +/* These two structures should use the same amount of 16-byte-aligned space */
> > > +static_assert(ALIGN(16, sizeof(struct smbios_entry)) ==
> > > +           ALIGN(16, sizeof(struct smbios3_entry)));
> > > +
> > >   /* BIOS characteristics */
> > >   #define BIOS_CHARACTERISTICS_PCI_SUPPORTED  (1 << 7)
> > >   #define BIOS_CHARACTERISTICS_UPGRADEABLE    (1 << 11)
> > > diff --git a/lib/smbios.c b/lib/smbios.c
> > > index c7a557bc9b7b..92e98388084f 100644
> > > --- a/lib/smbios.c
> > > +++ b/lib/smbios.c
> > > @@ -487,7 +487,11 @@ ulong write_smbios_table(ulong addr)
> > >       addr = ALIGN(addr, 16);
> > >       start_addr = addr;
> > >
> > > -     addr += sizeof(struct smbios_entry);
> > > +     /*
> > > +      * So far we don't know which struct will be used, but they both end
> > > +      * up using the same amount of 16-bit-aligned space
> > > +      */
> > > +     addr += max(sizeof(struct smbios_entry), sizeof(struct smbios3_entry));
> > >       addr = ALIGN(addr, 16);
> > >       tables = addr;
> > >
> > > @@ -512,14 +516,24 @@ ulong write_smbios_table(ulong addr)
> > >        * sandbox's DRAM buffer.
> > >        */
> > >       table_addr = (ulong)map_sysmem(tables, 0);
> > > -     if (sizeof(table_addr) > sizeof(u32) && table_addr > (ulong)UINT_MAX) {
> > > +     if (sizeof(table_addr) > sizeof(u32) && addr >= (ulong)UINT_MAX) {
> >
> > You have to check the end of the the last SMBIOS structure not the start
> > of the first SMBIOS structure against UINT_MAX.
> >
> > > +             struct smbios3_entry *se;
> > >               /*
> > >                * We need to put this >32-bit pointer into the table but the
> > >                * field is only 32 bits wide.
> > >                */
> > > -             printf("WARNING: SMBIOS table_address overflow %llx\n",
> > > -                    (unsigned long long)table_addr);
> > > -             addr = 0;
> > > +             printf("WARNING: Using SMBIOS3.0 due to table-address overflow %lx\n",
> > > +                    table_addr);
> >
> > This should be log_debug().
> >
> > > +             se = map_sysmem(start_addr, sizeof(struct smbios_entry));
> > > +             memset(se, '\0', sizeof(struct smbios_entry));
> > > +             memcpy(se->anchor, "_SM3_", 5);
> > > +             se->length = sizeof(struct smbios3_entry);
> > > +             se->major_ver = SMBIOS_MAJOR_VER;
> > > +             se->minor_ver = SMBIOS_MINOR_VER;
> > > +             se->docrev = 0;
> > > +             se->entry_point_rev = 1;
> > > +             se->max_struct_size = len;
> > > +             se->struct_table_address = table_addr;
> >
> > You must fill the checksum:
> >
> > se->checksum = table_compute_checksum(se, sizeof(struct smbios3_entry));
> >
> > With the checksum filled I can use dmidecode in Linux based on the
> > SMBIOS3 table:
> >
> > ubuntu at ubuntu:~$ sudo dmidecode
> > # dmidecode 3.5
> > # SMBIOS3 entry point at 0x27ef53000
> > Found SMBIOS entry point in EFI, reading table from /dev/mem.
> > SMBIOS 3.7.0 present.
> > # SMBIOS implementations newer than version 3.5.0 are not
> > # fully supported by this version of dmidecode.
> > Table at 0x27EF53020.
> >
> > Handle 0x0000, DMI type 0, 24 bytes
> > BIOS Information
> >          Vendor: U-Boot
>
> OK, great, thank you for figuring this out. Do you think this might be
> a reasonable solution for -next ?

What about [0] ? Do you expect this to land for 2024.01?
I think we should one or the other, unless this is a hotfix for the
upcoming release

[0] https://lore.kernel.org/u-boot/20231121025818.741258-1-sjg@chromium.org/

Thanks
/Ilias
>
> Regards,
> Simon