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| author | Andy Lutomirski <luto@kernel.org> | 2017-10-08 21:53:05 -0700 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2018-01-07 01:46:49 +0000 |
| commit | add19752eb782379610a01ea0d8cfce83cf071b0 (patch) | |
| tree | b48f6cd3468558bb3d37864e79d5e7305c323cf7 | |
| parent | 92f128b6ac894a4ad9e0d24de1d9e6919494111c (diff) | |
| download | linux-stable-add19752eb782379610a01ea0d8cfce83cf071b0.tar.gz linux-stable-add19752eb782379610a01ea0d8cfce83cf071b0.tar.bz2 linux-stable-add19752eb782379610a01ea0d8cfce83cf071b0.zip | |
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
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | arch/x86/kernel/reboot.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index a34bdddeca85..04da0bf5c314 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -357,6 +357,12 @@ void machine_real_restart(unsigned int type) lowmem_gdt[1] = GDT_ENTRY(0x009b, restart_pa, 0xffff); +#ifdef CONFIG_X86_64 + /* Exiting long mode will fail if CR4.PCIDE is set. */ + if (static_cpu_has(X86_FEATURE_PCID)) + clear_in_cr4(X86_CR4_PCIDE); +#endif + /* Jump to the identity-mapped low memory code */ restart_lowmem(type); } |