From: tip-bot for Andy Lutomirski <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: bp@alien8.de, tglx@linutronix.de, linux-kernel@vger.kernel.org,
mingo@kernel.org, hpa@zytor.com, rostedt@goodmis.org,
luto@kernel.org
Subject: [tip:x86/urgent] x86/mm/64: Fix reboot interaction with CR4.PCIDE
Date: Mon, 9 Oct 2017 04:36:01 -0700 [thread overview]
Message-ID: <tip-924c6b900cfdf376b07bccfd80e62b21914f8a5a@git.kernel.org> (raw)
In-Reply-To: <f1e7d965998018450a7a70c2823873686a8b21c0.1507524746.git.luto@kernel.org>
Commit-ID: 924c6b900cfdf376b07bccfd80e62b21914f8a5a
Gitweb: https://git.kernel.org/tip/924c6b900cfdf376b07bccfd80e62b21914f8a5a
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Sun, 8 Oct 2017 21:53:05 -0700
Committer: Thomas Gleixner <tglx@linutronix.de>
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) <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
---
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 */
next prev parent reply other threads:[~2017-10-09 11:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-09 4:53 [PATCH] x86/mm/64: Fix reboot interaction with CR4.PCIDE Andy Lutomirski
2017-10-09 11:36 ` tip-bot for Andy Lutomirski [this message]
2017-10-09 12:42 ` [tip:x86/urgent] " Steven Rostedt
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