diff mbox series

[PATCHv6,05/16] x86/cpu: Defer CR pinning setup until after EFI initialization

Message ID 20250620135325.3300848-6-kirill.shutemov@linux.intel.com
State New
Headers show
Series x86: Enable Linear Address Space Separation support | expand

Commit Message

Kirill A. Shutemov June 20, 2025, 1:53 p.m. UTC 
From: Alexander Shishkin <alexander.shishkin@linux.intel.com>

In order to map the EFI runtime services, set_virtual_address_map()
needs to be called, which resides in the lower half of the address
space. This means that LASS needs to be temporarily disabled around
this call. This can only be done before the CR pinning is set up.

Move CR pinning setup behind the EFI initialization.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/kernel/cpu/common.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 4f430be285de..1a779e302872 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2081,7 +2081,6 @@  static __init void identify_boot_cpu(void)
 	enable_sep_cpu();
 #endif
 	cpu_detect_tlb(&boot_cpu_data);
-	setup_cr_pinning();
 
 	tsx_init();
 	tdx_init();
@@ -2532,10 +2531,21 @@  void __init arch_cpu_finalize_init(void)
 
 	/*
 	 * This needs to follow the FPU initializtion, since EFI depends on it.
+	 *
+	 * It also needs to precede the CR pinning setup, because the CR4.LASS
+	 * bit has to be cleared temporarily in order to execute the
+	 * set_virtual_address_map() EFI call, which resides in lower addresses
+	 * and would trip LASS if enabled.
+	 *
+	 * Wrapping efi_enter_virtual_mode() into lass_stac()/clac() is not
+	 * enough because AC flag gates data accesses, but not instruction
+	 * fetch. Clearing the CR4 bit is required.
 	 */
 	if (efi_enabled(EFI_RUNTIME_SERVICES))
 		efi_enter_virtual_mode();
 
+	setup_cr_pinning();
+
 	/*
 	 * Ensure that access to the per CPU representation has the initial
 	 * boot CPU configuration.