x86/mm: Enable CR4.PCIDE on supported systems

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>

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 822ad36be17b79ab83649df672a2ed4d538ab1d2..9fc5968da8208b7f2176c28c09e750b71948cc4f 100644 (file)
--- 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)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index f4776a3afc8f9ef0236597cc7f059e0ee6b93c1f..aa1e7246b06b6e950fc7f735d5c9ba96907c4d6e 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -321,6 +321,25 @@ static __always_inline void setup_smap(struct cpuinfo_x86 *c)
        }
 }
 
+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_x86 *c)
        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."

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index ffa41591bff92fa7200d47a51265458ffeb8b031..cbef64b508e10cb1bb52dd8af18cea7211248fe5 100644 (file)
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -433,6 +433,12 @@ static void __init xen_init_cpuid_mask(void)
                ~((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 */