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

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On 5/18/22 23:03, Ard Biesheuvel wrote:
On Wed, 18 May 2022 at 11:57, Sunil V L <sunilvl@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxx>
Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@xxxxxxxxxxxxx>
---
  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.

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.

Best regards

Heinrich

+       }
+       return status;
+}
+
  efi_status_t check_platform_features(void)
  {
         int ret;
+       efi_status_t status;

-       ret = get_boot_hartid_from_fdt();
-       if (ret) {
-               efi_err("/chosen/boot-hartid missing or invalid!\n");
-               return EFI_UNSUPPORTED;
+       status = get_boot_hartid_from_efi();
+       if (status != EFI_SUCCESS) {
+               ret = get_boot_hartid_from_fdt();
+               if (ret) {
+                       efi_err("Failed to get boot hartid!\n");
+                       return EFI_UNSUPPORTED;
+               }
         }
         return EFI_SUCCESS;
  }
diff --git a/include/linux/efi.h b/include/linux/efi.h
index ccd4d3f91c98..9822c730207c 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -380,6 +380,7 @@ void efi_native_runtime_setup(void);
  #define EFI_CONSOLE_OUT_DEVICE_GUID            EFI_GUID(0xd3b36f2c, 0xd551, 0x11d4,  0x9a, 0x46, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d)
  #define APPLE_PROPERTIES_PROTOCOL_GUID         EFI_GUID(0x91bd12fe, 0xf6c3, 0x44fb,  0xa5, 0xb7, 0x51, 0x22, 0xab, 0x30, 0x3a, 0xe0)
  #define EFI_TCG2_PROTOCOL_GUID                 EFI_GUID(0x607f766c, 0x7455, 0x42be,  0x93, 0x0b, 0xe4, 0xd7, 0x6d, 0xb2, 0x72, 0x0f)
+#define RISCV_EFI_BOOT_PROTOCOL_GUID           EFI_GUID(0xccd15fec, 0x6f73, 0x4eec,  0x83, 0x95, 0x3e, 0x69, 0xe4, 0xb9, 0x40, 0xbf)
  #define EFI_LOAD_FILE_PROTOCOL_GUID            EFI_GUID(0x56ec3091, 0x954c, 0x11d2,  0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b)
  #define EFI_LOAD_FILE2_PROTOCOL_GUID           EFI_GUID(0x4006c0c1, 0xfcb3, 0x403e,  0x99, 0x6d, 0x4a, 0x6c, 0x87, 0x24, 0xe0, 0x6d)
  #define EFI_RT_PROPERTIES_TABLE_GUID           EFI_GUID(0xeb66918a, 0x7eef, 0x402a,  0x84, 0x2e, 0x93, 0x1d, 0x21, 0xc3, 0x8a, 0xe9)
--
2.25.1




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