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| author | Andy Lutomirski <luto@kernel.org> | 2017-10-08 21:53:05 -0700 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2017-10-09 13:31:04 +0200 |
| commit | 924c6b900cfdf376b07bccfd80e62b21914f8a5a (patch) | |
| tree | 9b85f57af2c7b646e284b194636d925c6e265e7a | |
| parent | b664d57f39d01e775204d4f1a7e2f8bda77bc549 (diff) | |
| download | linux-924c6b900cfdf376b07bccfd80e62b21914f8a5a.tar.bz2 | |
x86/mm/64: Fix reboot interaction with CR4.PCIDE
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
| -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 54180fa6f66f..add33f600531 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -105,6 +105,10 @@ 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 */ |