[PATCH v2 4/4] x86/efistub: Don't bother enabling SEV in the EFI stub

Ard Biesheuvel
2025-04-16T16:58:09Z

One of the last things the EFI stub does before handing over to the core
kernel when booting as a SEV guest is enabling SEV, even though this is
mostly redundant: one of the first things the core kernel does is
calling sme_enable(), after setting up the early GDT and IDT but before
even setting up the kernel page tables.

So let's just drop this call to sev_enable(), and rely on the core
kernel to initiaize SEV correctly.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/include/asm/sev.h | 2 --
drivers/firmware/efi/libstub/x86-stub.c | 6 ------
2 files changed, 8 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 8637a65973ef..d762cc0fd47e 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -443,7 +443,6 @@ static __always_inline void sev_es_nmi_complete(void)
__sev_es_nmi_complete();
}
extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
-extern void sev_enable(struct boot_params *bp);

/*
* RMPADJUST modifies the RMP permissions of a page of a lesser-
@@ -531,7 +530,6 @@ static inline void sev_es_ist_exit(void) { }
static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; }
static inline void sev_es_nmi_complete(void) { }
static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
-static inline void sev_enable(struct boot_params *bp) { }
static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate) { return 0; }
static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs) { return 0; }
static inline void setup_ghcb(void) { }
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index d9ae1a230d39..6b4f5ac91e7f 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -936,12 +936,6 @@ void __noreturn efi_stub_entry(efi_handle_t handle,
goto fail;
}

- /*
- * Call the SEV init code while still running with the firmware's
- * GDT/IDT, so #VC exceptions will be handled by EFI.
- */
- sev_enable(boot_params);
-
efi_5level_switch();

enter_kernel(kernel_entry, boot_params);
--
2.49.0.805.g082f7c87e0-goog