Patch "x86/mm: Enable CR4.PCIDE on supported systems" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    x86/mm: Enable CR4.PCIDE on supported systems

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-mm-enable-cr4.pcide-on-supported-systems.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 660da7c9228f685b2ebe664f9fd69aaddcc420b5 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@kernel.org>
Date: Thu, 29 Jun 2017 08:53:21 -0700
Subject: x86/mm: Enable CR4.PCIDE on supported systems

From: Andy Lutomirski <luto@kernel.org>

commit 660da7c9228f685b2ebe664f9fd69aaddcc420b5 upstream.

We can use PCID if the CPU has PCID and PGE and we're not on Xen.

By itself, this has no effect. A followup patch will start using PCID.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Nadav Amit <nadav.amit@gmail.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/6327ecd907b32f79d5aa0d466f04503bbec5df88.1498751203.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/include/asm/tlbflush.h |    8 ++++++++
 arch/x86/kernel/cpu/common.c    |   22 ++++++++++++++++++++++
 arch/x86/xen/enlighten.c        |    6 ++++++
 3 files changed, 36 insertions(+)

--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -190,6 +190,14 @@ static inline void __flush_tlb_all(void)
 		__flush_tlb_global();
 	else
 		__flush_tlb();
+
+	/*
+	 * Note: if we somehow had PCID but not PGE, then this wouldn't work --
+	 * we'd end up flushing kernel translations for the current ASID but
+	 * we might fail to flush kernel translations for other cached ASIDs.
+	 *
+	 * To avoid this issue, we force PCID off if PGE is off.
+	 */
 }
 
 static inline void __flush_tlb_one(unsigned long addr)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -321,6 +321,25 @@ static __always_inline void setup_smap(s
 	}
 }
 
+static void setup_pcid(struct cpuinfo_x86 *c)
+{
+	if (cpu_has(c, X86_FEATURE_PCID)) {
+		if (cpu_has(c, X86_FEATURE_PGE)) {
+			cr4_set_bits(X86_CR4_PCIDE);
+		} else {
+			/*
+			 * flush_tlb_all(), as currently implemented, won't
+			 * work if PCID is on but PGE is not.  Since that
+			 * combination doesn't exist on real hardware, there's
+			 * no reason to try to fully support it, but it's
+			 * polite to avoid corrupting data if we're on
+			 * an improperly configured VM.
+			 */
+			clear_cpu_cap(c, X86_FEATURE_PCID);
+		}
+	}
+}
+
 /*
  * Some CPU features depend on higher CPUID levels, which may not always
  * be available due to CPUID level capping or broken virtualization
@@ -952,6 +971,9 @@ static void identify_cpu(struct cpuinfo_
 	setup_smep(c);
 	setup_smap(c);
 
+	/* Set up PCID */
+	setup_pcid(c);
+
 	/*
 	 * The vendor-specific functions might have changed features.
 	 * Now we do "generic changes."
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -433,6 +433,12 @@ static void __init xen_init_cpuid_mask(v
 		~((1 << X86_FEATURE_MTRR) |  /* disable MTRR */
 		  (1 << X86_FEATURE_ACC));   /* thermal monitoring */
 
+	/*
+	 * Xen PV would need some work to support PCID: CR3 handling as well
+	 * as xen_flush_tlb_others() would need updating.
+	 */
+	cpuid_leaf1_ecx_mask &= ~(1 << X86_FEATURE_PCID);  /* disable PCID */
+
 	if (!xen_initial_domain())
 		cpuid_leaf1_edx_mask &=
 			~((1 << X86_FEATURE_ACPI));  /* disable ACPI */


Patches currently in stable-queue which might be from luto@kernel.org are

queue-4.4/x86-vm86-32-switch-to-flush_tlb_mm_range-in-mark_screen_rdonly.patch
queue-4.4/x86-mm-add-the-nopcid-boot-option-to-turn-off-pcid.patch
queue-4.4/x86-mm-enable-cr4.pcide-on-supported-systems.patch
queue-4.4/x86-mm-remove-the-up-asm-tlbflush.h-code-always-use-the-formerly-smp-code.patch
queue-4.4/x86-mm-reimplement-flush_tlb_page-using-flush_tlb_mm_range.patch
queue-4.4/x86-mm-make-flush_tlb_mm_range-more-predictable.patch
queue-4.4/x86-mm-remove-flush_tlb-and-flush_tlb_current_task.patch
queue-4.4/x86-mm-disable-pcid-on-32-bit-kernels.patch
queue-4.4/x86-mm-64-fix-reboot-interaction-with-cr4.pcide.patch