On Mon, 9 Oct 2017 04:36:01 -0700 tip-bot for Andy Lutomirski <[email protected]> wrote:
> Commit-ID: 924c6b900cfdf376b07bccfd80e62b21914f8a5a > Gitweb: > https://git.kernel.org/tip/924c6b900cfdf376b07bccfd80e62b21914f8a5a > Author: Andy Lutomirski <[email protected]> > AuthorDate: Sun, 8 Oct 2017 21:53:05 -0700 > Committer: Thomas Gleixner <[email protected]> > CommitDate: Mon, 9 Oct 2017 13:31:04 +0200 > > 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) <[email protected]> Didn't someone somewhere say not to combine tags? Have them always be separate. I noticed they were separate when Andy submitted it, but I'm assuming that Thomas combined it. -- Steve > Signed-off-by: Andy Lutomirski <[email protected]> > Signed-off-by: Thomas Gleixner <[email protected]> > Cc: Borislav Petkov <[email protected]> > Link: > https://lkml.kernel.org/r/f1e7d965998018450a7a70c2823873686a8b21c0.1507524746.git.l...@kernel.org > > --- > arch/x86/kernel/reboot.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c > index 54180fa..add33f6 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 */
