[PATCH V4 1/1] riscv/efi_stub: Add support for RISCV_EFI_BOOT_PROTOCOL

[Sunil V L]

On Thu, May 19, 2022 at 11:07:28AM -0700, Atish Patra wrote:
> On Thu, May 19, 2022 at 1:14 AM Ard Biesheuvel <ardb at kernel.org> wrote:
> >
> > On Thu, 19 May 2022 at 08:17, Heinrich Schuchardt
> > <heinrich.schuchardt at canonical.com> wrote:
> > >
> > >
> > >
> > > On 5/18/22 23:03, Ard Biesheuvel wrote:
> > > > On Wed, 18 May 2022 at 11:57, Sunil V L <sunilvl at ventanamicro.com> wrote:
> > > >>
> > > >> This patch adds the support for getting the boot hart ID in
> > > >> Linux EFI stub using RISCV_EFI_BOOT_PROTOCOL. This protocol
> > > >> is preferred method over existing DT based solution since it
> > > >> works irrespective of DT or ACPI.
> > > >>
> > > >> The specification of the protocol is hosted at:
> > > >> https://github.com/riscv-non-isa/riscv-uefi
> > > >>
> > > >> Signed-off-by: Sunil V L <sunilvl at ventanamicro.com>
> > > >> Acked-by: Palmer Dabbelt <palmer at rivosinc.com>
> > > >> Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> > > >> ---
> > > >>   drivers/firmware/efi/libstub/efistub.h    |  7 ++++++
> > > >>   drivers/firmware/efi/libstub/riscv-stub.c | 29 +++++++++++++++++++----
> > > >>   include/linux/efi.h                       |  1 +
> > > >>   3 files changed, 32 insertions(+), 5 deletions(-)
> > > >>
> > > >> diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
> > > >> index edb77b0621ea..aced62a0907e 100644
> > > >> --- a/drivers/firmware/efi/libstub/efistub.h
> > > >> +++ b/drivers/firmware/efi/libstub/efistub.h
> > > >> @@ -720,6 +720,13 @@ union efi_tcg2_protocol {
> > > >>          } mixed_mode;
> > > >>   };
> > > >>
> > > >> +struct riscv_efi_boot_protocol {
> > > >> +       u64 revision;
> > > >> +
> > > >> +       efi_status_t (__efiapi * get_boot_hartid)(struct riscv_efi_boot_protocol *this,
> > > >> +                                                 size_t *boot_hartid);
> > > >
> > > > size_t is not a EFI type, and your spec uses UINTN here, which is
> > > > equivalent to 'unsigned long'. However, jump_kernel_func() takes a
> > > > unsigned int for the hartid. Please clean this up.
> > >
> > > unsigned long and size_t have the same number of bits. This seems to be
> > > a question of taste where we should follow the maintainer.
> > >
> >
> > We use unsigned long wherever the UEFI spec uses UINTN. This is not a
> > matter of taste, really.
> >
> > > jump_kernel_func() assuming boot hart ID to be an unsigned int is not in
> > > line with the RISC-V ISA which allows to use all xlen bits.
> > >
> > > >
> > > >
> > > >> +};
> > > >> +
> > > >>   typedef union efi_load_file_protocol efi_load_file_protocol_t;
> > > >>   typedef union efi_load_file_protocol efi_load_file2_protocol_t;
> > > >>
> > > >> diff --git a/drivers/firmware/efi/libstub/riscv-stub.c b/drivers/firmware/efi/libstub/riscv-stub.c
> > > >> index 9c460843442f..012504f6f9a4 100644
> > > >> --- a/drivers/firmware/efi/libstub/riscv-stub.c
> > > >> +++ b/drivers/firmware/efi/libstub/riscv-stub.c
> > > >> @@ -23,7 +23,7 @@
> > > >>
> > > >>   typedef void __noreturn (*jump_kernel_func)(unsigned int, unsigned long);
> > > >>
> > > >> -static u32 hartid;
> > > >> +static size_t hartid;
> > > >>
> > > >
> > > > and here
> > > >
> > > >>   static int get_boot_hartid_from_fdt(void)
> > > >>   {
> > > >> @@ -47,14 +47,33 @@ static int get_boot_hartid_from_fdt(void)
> > > >>          return 0;
> > > >>   }
> > > >>
> > > >> +static efi_status_t get_boot_hartid_from_efi(void)
> > > >> +{
> > > >> +       efi_guid_t boot_protocol_guid = RISCV_EFI_BOOT_PROTOCOL_GUID;
> > > >> +       efi_status_t status;
> > > >> +       struct riscv_efi_boot_protocol *boot_protocol;
> > > >> +
> > > >> +       status = efi_bs_call(locate_protocol, &boot_protocol_guid, NULL,
> > > >> +                            (void **)&boot_protocol);
> > > >> +       if (status == EFI_SUCCESS) {
> > > >> +               status = efi_call_proto(boot_protocol,
> > > >> +                                       get_boot_hartid, &hartid);
> > >
> > > A lot of the kernel code seems to be unfit to handle hart IDs exceeding
> > > INT_MAX (e.g. sbi_cpu_is_stopped()). Until this is fixed we have to
> > > treat hartid > INT_MAX as an error.
> > >
> >
> > This is an issue in the core kernel code, not in the EFI stub. As you
> > pointed out, the ISA implies UINTN / unsigned long here, and if the
> > startup code cannot deal with that, it can be fixed separately.
> 
> It was kept as unsigned int because hartid > INT_MAX is very unlikely to happen.
> But I agree that we should just follow the spec(allowing XLEN bits for
> hartid) and
> change "unsigned int" to "unsigned long" wherever hartid is concerned.
> 
> As the hartid is changed to unsigned long, get_boot_hartid_from_fdt
> should be fixed as well.
> Currently, it is using fdt32_to_cpu.

I am working on a separate patch series to modify these instances. Will send
soon for your feedback.

Thanks
Sunil
> 
> 
> 
> --
> Regards,
> Atish