diff options
| author | Andy Lutomirski <luto@kernel.org> | 2017-10-08 21:53:05 -0700 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2018-01-09 00:35:13 +0000 |
| commit | 7ebf71f82595bc72f9308d7bb193367cd6534f25 (patch) | |
| tree | d4f3b668e0d7053ee0b8859be17cb68601c1de0c | |
| parent | 7e031825d38f43a6c2a5b1010c2c087e57bfc853 (diff) | |
x86/mm/64: Fix reboot interaction with CR4.PCIDE
commit 924c6b900cfdf376b07bccfd80e62b21914f8a5a upstream.
Trying to reboot via real mode fails with PCID on: long mode cannot
be exited while CR4.PCIDE is set. (No, I have no idea why, but the
SDM and actual CPUs are in agreement here.) The result is a GPF and
a hang instead of a reboot.
I didn't catch this in testing because neither my computer nor my VM
reboots this way. I can trigger it with reboot=bios, though.
Fixes: 660da7c9228f ("x86/mm: Enable CR4.PCIDE on supported systems")
Reported-and-tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Link: https://lkml.kernel.org/r/f1e7d965998018450a7a70c2823873686a8b21c0.1507524746.git.luto@kernel.org
Cc: Hugh Dickins <hughd@google.com>
[bwh: Backported to 3.16: use clear_in_cr4()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | arch/x86/kernel/reboot.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index 5e8c0f1c99c4..281aa6bcafd9 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -92,6 +92,10 @@ void __noreturn machine_real_restart(unsigned int type) load_cr3(initial_page_table); #else write_cr3(real_mode_header->trampoline_pgd); + + /* Exiting long mode will fail if CR4.PCIDE is set. */ + if (static_cpu_has(X86_FEATURE_PCID)) + cr4_clear_bits(X86_CR4_PCIDE); #endif /* Jump to the identity-mapped low memory code */ |