[PATCH 4.9 21/75] x86/mm: Enable CR4.PCIDE on supported systems

Greg Kroah-Hartman
2018-01-01T15:22:25Z

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
@@ -191,6 +191,14 @@ 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
@@ -324,6 +324,25 @@ 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);
+ }
+ }
+}
+
/*
* Protection Keys are not available in 32-bit mode.
*/
@@ -1082,6 +1101,9 @@ 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
@@ -444,6 +444,12 @@ 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 % 32)); /* disable PCID */
+
if (!xen_initial_domain())
cpuid_leaf1_edx_mask &=
~((1 << X86_FEATURE_ACPI)); /* disable ACPI */