[PATCH v10 28/45] x86/compressed/acpi: Move EFI kexec handling into common code

Brijesh Singh
2022-02-09T18:12:24Z

From: Michael Roth <michael.roth@amd.com>

Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally move the related code
into a set of helpers that can be re-used for that purpose.

In this instance, the current acpi.c kexec handling is mainly used to
get the alternative EFI config table address provided by kexec via a
setup_data entry of type SETUP_EFI. If not present, the code then falls
back to normal EFI config table address provided by EFI system table.
This would need to be done by all call-sites attempting to access the
EFI config table, so just have efi_get_conf_table() handle that
automatically.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/boot/compressed/acpi.c | 59 ---------------------------------
arch/x86/boot/compressed/efi.c | 46 ++++++++++++++++++++++++-
2 files changed, 45 insertions(+), 60 deletions(-)

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index b0c1dffc5510..64b172dabd5c 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -47,57 +47,6 @@ __efi_get_rsdp_addr(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len)
return 0;
}

-/* EFI/kexec support is 64-bit only. */
-#ifdef CONFIG_X86_64
-static struct efi_setup_data *get_kexec_setup_data_addr(void)
-{
- struct setup_data *data;
- u64 pa_data;
-
- pa_data = boot_params->hdr.setup_data;
- while (pa_data) {
- data = (struct setup_data *)pa_data;
- if (data->type == SETUP_EFI)
- return (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
-
- pa_data = data->next;
- }
- return NULL;
-}
-
-static acpi_physical_address kexec_get_rsdp_addr(void)
-{
- efi_system_table_64_t *systab;
- struct efi_setup_data *esd;
- struct efi_info *ei;
- enum efi_type et;
-
- esd = (struct efi_setup_data *)get_kexec_setup_data_addr();
- if (!esd)
- return 0;
-
- if (!esd->tables) {
- debug_putstr("Wrong kexec SETUP_EFI data.\n");
- return 0;
- }
-
- et = efi_get_type(boot_params);
- if (et != EFI_TYPE_64) {
- debug_putstr("Unexpected kexec EFI environment (expected 64-bit EFI).\n");
- return 0;
- }
-
- /* Get systab from boot params. */
- systab = (efi_system_table_64_t *)efi_get_system_table(boot_params);
- if (!systab)
- error("EFI system table not found in kexec boot_params.");
-
- return __efi_get_rsdp_addr((unsigned long)esd->tables, systab->nr_tables);
-}
-#else
-static acpi_physical_address kexec_get_rsdp_addr(void) { return 0; }
-#endif /* CONFIG_X86_64 */
-
static acpi_physical_address efi_get_rsdp_addr(void)
{
#ifdef CONFIG_EFI
@@ -210,14 +159,6 @@ acpi_physical_address get_rsdp_addr(void)

pa = boot_params->acpi_rsdp_addr;

- /*
- * Try to get EFI data from setup_data. This can happen when we're a
- * kexec'ed kernel and kexec(1) has passed all the required EFI info to
- * us.
- */
- if (!pa)
- pa = kexec_get_rsdp_addr();
-
if (!pa)
pa = efi_get_rsdp_addr();

diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
index f8d26db22659..ff2e2eaba1d4 100644
--- a/arch/x86/boot/compressed/efi.c
+++ b/arch/x86/boot/compressed/efi.c
@@ -78,6 +78,46 @@ unsigned long efi_get_system_table(struct boot_params *bp)
return sys_tbl_pa;
}

+/*
+ * EFI config table address changes to virtual address after boot, which may
+ * not be accessible for the kexec'd kernel. To address this, kexec provides
+ * the initial physical address via a struct setup_data entry, which is
+ * checked for here, along with some sanity checks.
+ */
+static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp,
+ enum efi_type et)
+{
+#ifdef CONFIG_X86_64
+ struct efi_setup_data *esd = NULL;
+ struct setup_data *data;
+ u64 pa_data;
+
+ pa_data = bp->hdr.setup_data;
+ while (pa_data) {
+ data = (struct setup_data *)pa_data;
+ if (data->type == SETUP_EFI) {
+ esd = (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
+ break;
+ }
+
+ pa_data = data->next;
+ }
+
+ /*
+ * Original ACPI code falls back to attempting normal EFI boot in these
+ * cases, so maintain existing behavior by indicating non-kexec
+ * environment to the caller, but print them for debugging.
+ */
+ if (esd && !esd->tables) {
+ debug_putstr("kexec EFI environment missing valid configuration table.\n");
+ return NULL;
+ }
+
+ return esd;
+#endif
+ return NULL;
+}
+
/**
* efi_get_conf_table - Given a pointer to boot_params, locate and return the physical
* address of EFI configuration table.
@@ -106,8 +146,12 @@ int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa,
et = efi_get_type(bp);
if (et == EFI_TYPE_64) {
efi_system_table_64_t *stbl = (efi_system_table_64_t *)sys_tbl_pa;
+ struct efi_setup_data *esd;

- *cfg_tbl_pa = stbl->tables;
+ /* kexec provides an alternative EFI conf table, check for it. */
+ esd = get_kexec_setup_data(bp, et);
+
+ *cfg_tbl_pa = esd ? esd->tables : stbl->tables;
*cfg_tbl_len = stbl->nr_tables;
} else if (et == EFI_TYPE_32) {
efi_system_table_32_t *stbl = (efi_system_table_32_t *)sys_tbl_pa;
--
2.25.1