Commit 33e20b07 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86/realmode: Make stack lock work in trampoline_compat() 



The stack locking and stack assignment macro LOAD_REALMODE_ESP fails to
work when invoked from the 64bit trampoline entry point:

trampoline_start64
  trampoline_compat
    LOAD_REALMODE_ESP <- lock

Accessing tr_lock is only possible from 16bit mode. For the compat entry
point this needs to be pa_tr_lock so that the required relocation entry is
generated. Otherwise it locks the non-relocated address which is
aside of being wrong never cleared in secondary_startup_64() causing all
but the first CPU to get stuck on the lock.

Make the macro take an argument lock_pa which defaults to 0 and rename it
to LOCK_AND_LOAD_REALMODE_ESP to make it clear what this is about.

Fixes: f6f1ae91 ("x86/smpboot: Implement a bit spinlock to protect the realmode stack")
Reported-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/87h6rujdvl.ffs@tglx
parent 5da80b28

arch/x86/realmode/rm/trampoline_64.S

+8 −4
Original line number Diff line number Diff line
@@ -37,12 +37,16 @@ 
	.text

	.code16



.macro LOAD_REALMODE_ESP

.macro LOCK_AND_LOAD_REALMODE_ESP lock_pa=0

	/*

	 * Make sure only one CPU fiddles with the realmode stack

	 */

.Llock_rm\@:

	.if \lock_pa

        lock btsl       $0, pa_tr_lock

	.else

        lock btsl       $0, tr_lock

	.endif

        jnc             2f

        pause

        jmp             .Llock_rm\@
@@ -63,7 +67,7 @@ SYM_CODE_START(trampoline_start) 
	mov	%ax, %es

	mov	%ax, %ss



	LOAD_REALMODE_ESP

	LOCK_AND_LOAD_REALMODE_ESP



	call	verify_cpu		# Verify the cpu supports long mode

	testl   %eax, %eax		# Check for return code
@@ -106,7 +110,7 @@ SYM_CODE_START(sev_es_trampoline_start) 
	mov	%ax, %es

	mov	%ax, %ss



	LOAD_REALMODE_ESP

	LOCK_AND_LOAD_REALMODE_ESP



	jmp	.Lswitch_to_protected

SYM_CODE_END(sev_es_trampoline_start)
@@ -189,7 +193,7 @@ SYM_CODE_START(pa_trampoline_compat) 
	 * In compatibility mode.  Prep ESP and DX for startup_32, then disable

	 * paging and complete the switch to legacy 32-bit mode.

	 */

	LOAD_REALMODE_ESP

	LOCK_AND_LOAD_REALMODE_ESP lock_pa=1

	movw	$__KERNEL_DS, %dx



	movl	$(CR0_STATE & ~X86_CR0_PG), %eax