[PATCH v3 71/75] x86/head/64: Don't call verify_cpu() on starting APs

Joerg Roedel
2020-04-28T15:19:00Z

From: Joerg Roedel <jroedel@suse.de>

The APs are not ready to handle exceptions when verify_cpu() is called
in secondary_startup_64.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/include/asm/realmode.h | 1 +
arch/x86/kernel/head_64.S | 1 +
arch/x86/realmode/init.c | 6 ++++++
3 files changed, 8 insertions(+)

diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
index 6590394af309..5c97807c38a4 100644
--- a/arch/x86/include/asm/realmode.h
+++ b/arch/x86/include/asm/realmode.h
@@ -69,6 +69,7 @@ extern unsigned char startup_32_smp[];
extern unsigned char boot_gdt[];
#else
extern unsigned char secondary_startup_64[];
+extern unsigned char secondary_startup_64_no_verify[];
#endif

static inline size_t real_mode_size_needed(void)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 7f2d5e14db73..72b8f0834de1 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -150,6 +150,7 @@ SYM_CODE_START(secondary_startup_64)
/* Sanitize CPU configuration */
call verify_cpu

+SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
/*
* Retrieve the modifier (SME encryption mask if SME is active) to be
* added to the initial pgdir entry that will be programmed into CR3.
diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
index 1c5cbfd102d5..030c38268069 100644
--- a/arch/x86/realmode/init.c
+++ b/arch/x86/realmode/init.c
@@ -109,6 +109,12 @@ static void __init setup_real_mode(void)
trampoline_header->flags |= TH_FLAGS_SME_ACTIVE;

if (sev_es_active()) {
+ /*
+ * Skip the call to verify_cpu() in secondary_startup_64 as it
+ * will cause #VC exceptions when the AP can't handle them yet.
+ */
+ trampoline_header->start = (u64) secondary_startup_64_no_verify;
+
if (sev_es_setup_ap_jump_table(real_mode_header))
panic("Failed to update SEV-ES AP Jump Table");
}
--
2.17.1