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| author | Thomas Gleixner <tglx@linutronix.de> | 2023-05-30 12:46:22 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2023-05-30 14:11:47 +0200 |
| commit | 33e20b07bec4991c169e3c6ff28c2126583724fc (patch) | |
| tree | d4995aef3605ac5ee4e899500af620b54f449a4e /arch/x86/realmode | |
| parent | 5da80b28bf25c3458c7beb23794ff53622ce7eb4 (diff) | |
| download | lwn-33e20b07bec4991c169e3c6ff28c2126583724fc.tar.gz lwn-33e20b07bec4991c169e3c6ff28c2126583724fc.zip | |
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: f6f1ae9128d2 ("x86/smpboot: Implement a bit spinlock to protect the realmode stack")
Reported-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/87h6rujdvl.ffs@tglx
Diffstat (limited to 'arch/x86/realmode')
| -rw-r--r-- | arch/x86/realmode/rm/trampoline_64.S | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/arch/x86/realmode/rm/trampoline_64.S b/arch/x86/realmode/rm/trampoline_64.S index 4822ad2a5e89..c9f76fae902e 100644 --- a/arch/x86/realmode/rm/trampoline_64.S +++ b/arch/x86/realmode/rm/trampoline_64.S @@ -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 |