[xen stable-4.7] xen/x86: use invpcid for flushing the TLB

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[xen stable-4.7] xen/x86: use invpcid for flushing the TLB

patchbot
commit acdf07d3f02b177604d79da07917eb2e44a4f53f
Author:     Juergen Gross <[hidden email]>
AuthorDate: Thu Apr 26 13:33:13 2018 +0200
Commit:     Jan Beulich <[hidden email]>
CommitDate: Tue May 29 10:44:19 2018 +0200

    xen/x86: use invpcid for flushing the TLB
   
    If possible use the INVPCID instruction for flushing the TLB instead of
    toggling cr4.pge for that purpose.
   
    While at it remove the dependency on cr4.pge being required for mtrr
    loading, as this will be required later anyway.
   
    Add a command line option "invpcid" for controlling the use of
    INVPCID (default to true).
   
    Signed-off-by: Juergen Gross <[hidden email]>
    Reviewed-by: Jan Beulich <[hidden email]>
---
 docs/misc/xen-command-line.markdown |  9 +++++++
 xen/arch/x86/cpu/mtrr/generic.c     | 47 ++++++++++++++++++++-----------------
 xen/arch/x86/flushtlb.c             | 29 +++++++++++++++--------
 xen/arch/x86/setup.c                |  8 +++++++
 xen/include/asm-x86/invpcid.h       |  2 ++
 5 files changed, 63 insertions(+), 32 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index 843b3e82ba..f5c477f228 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1205,6 +1205,15 @@ Because responsibility for APIC setup is shared between Xen and the
 domain 0 kernel this option is automatically propagated to the domain
 0 command line.
 
+### invpcid (x86)
+> `= <boolean>`
+
+> Default: `true`
+
+By default, Xen will use the INVPCID instruction for TLB management if
+it is available.  This option can be used to cause Xen to fall back to
+older mechanisms, which are generally slower.
+
 ### noirqbalance
 > `= <boolean>`
 
diff --git a/xen/arch/x86/cpu/mtrr/generic.c b/xen/arch/x86/cpu/mtrr/generic.c
index 234d2ba50b..2a0feff6b2 100644
--- a/xen/arch/x86/cpu/mtrr/generic.c
+++ b/xen/arch/x86/cpu/mtrr/generic.c
@@ -4,6 +4,7 @@
 #include <xen/init.h>
 #include <xen/mm.h>
 #include <asm/flushtlb.h>
+#include <asm/invpcid.h>
 #include <asm/io.h>
 #include <asm/mtrr.h>
 #include <asm/msr.h>
@@ -390,7 +391,6 @@ static unsigned long set_mtrr_state(void)
 }
 
 
-static unsigned long cr4 = 0;
 static DEFINE_SPINLOCK(set_atomicity_lock);
 
 /*
@@ -400,9 +400,9 @@ static DEFINE_SPINLOCK(set_atomicity_lock);
  * has been called.
  */
 
-static void prepare_set(void)
+static bool_t prepare_set(void)
 {
- unsigned long cr0;
+ unsigned long cr0, cr4;
 
  /*  Note that this is not ideal, since the cache is only flushed/disabled
    for this CPU while the MTRRs are changed, but changing this requires
@@ -415,36 +415,38 @@ static void prepare_set(void)
  write_cr0(cr0);
  wbinvd();
 
- /*  Save value of CR4 and clear Page Global Enable (bit 7)  */
- if ( cpu_has_pge ) {
- cr4 = read_cr4();
+ cr4 = read_cr4();
+ if (cr4 & X86_CR4_PGE)
  write_cr4(cr4 & ~X86_CR4_PGE);
- }
-
- /* Flush all TLBs via a mov %cr3, %reg; mov %reg, %cr3 */
- flush_tlb_local();
+ else if (use_invpcid)
+ invpcid_flush_all();
+ else
+ write_cr3(read_cr3());
 
  /*  Save MTRR state */
  rdmsrl(MSR_MTRRdefType, deftype);
 
  /*  Disable MTRRs, and set the default type to uncached  */
  mtrr_wrmsr(MSR_MTRRdefType, deftype & ~0xcff);
+
+ return cr4 & X86_CR4_PGE;
 }
 
-static void post_set(void)
+static void post_set(bool_t pge)
 {
- /*  Flush TLBs (no need to flush caches - they are disabled)  */
- flush_tlb_local();
-
  /* Intel (P6) standard MTRRs */
  mtrr_wrmsr(MSR_MTRRdefType, deftype);
 
  /*  Enable caches  */
  write_cr0(read_cr0() & 0xbfffffff);
 
- /*  Restore value of CR4  */
- if ( cpu_has_pge )
- write_cr4(cr4);
+ if (pge)
+ write_cr4(read_cr4() | X86_CR4_PGE);
+ else if (use_invpcid)
+ invpcid_flush_all();
+ else
+ write_cr3(read_cr3());
+
  spin_unlock(&set_atomicity_lock);
 }
 
@@ -452,14 +454,15 @@ static void generic_set_all(void)
 {
  unsigned long mask, count;
  unsigned long flags;
+ bool_t pge;
 
  local_irq_save(flags);
- prepare_set();
+ pge = prepare_set();
 
  /* Actually set the state */
  mask = set_mtrr_state();
 
- post_set();
+ post_set(pge);
  local_irq_restore(flags);
 
  /*  Use the atomic bitops to update the global mask  */
@@ -468,7 +471,6 @@ static void generic_set_all(void)
  set_bit(count, &smp_changes_mask);
  mask >>= 1;
  }
-
 }
 
 static void generic_set_mtrr(unsigned int reg, unsigned long base,
@@ -485,11 +487,12 @@ static void generic_set_mtrr(unsigned int reg, unsigned long base,
 {
  unsigned long flags;
  struct mtrr_var_range *vr;
+ bool_t pge;
 
  vr = &mtrr_state.var_ranges[reg];
 
  local_irq_save(flags);
- prepare_set();
+ pge = prepare_set();
 
  if (size == 0) {
  /* The invalid bit is kept in the mask, so we simply clear the
@@ -510,7 +513,7 @@ static void generic_set_mtrr(unsigned int reg, unsigned long base,
  mtrr_wrmsr(MSR_IA32_MTRR_PHYSMASK(reg), vr->mask);
  }
 
- post_set();
+ post_set(pge);
  local_irq_restore(flags);
 }
 
diff --git a/xen/arch/x86/flushtlb.c b/xen/arch/x86/flushtlb.c
index e204b0a1e0..b619cb2de6 100644
--- a/xen/arch/x86/flushtlb.c
+++ b/xen/arch/x86/flushtlb.c
@@ -12,6 +12,7 @@
 #include <xen/smp.h>
 #include <xen/softirq.h>
 #include <asm/flushtlb.h>
+#include <asm/invpcid.h>
 #include <asm/page.h>
 
 /* Debug builds: Wrap frequently to stress-test the wrap logic. */
@@ -73,6 +74,23 @@ static void post_flush(u32 t)
     this_cpu(tlbflush_time) = t;
 }
 
+static void do_tlb_flush(void)
+{
+    u32 t = pre_flush();
+
+    if ( use_invpcid )
+        invpcid_flush_all();
+    else
+    {
+        unsigned long cr4 = read_cr4();
+
+        write_cr4(cr4 ^ X86_CR4_PGE);
+        write_cr4(cr4);
+    }
+
+    post_flush(t);
+}
+
 void switch_cr3(unsigned long cr3)
 {
     unsigned long flags, cr4;
@@ -120,16 +138,7 @@ unsigned int flush_area_local(const void *va, unsigned int flags)
                            : : "m" (*(const char *)(va)) : "memory" );
         }
         else
-        {
-            u32 t = pre_flush();
-            unsigned long cr4 = read_cr4();
-
-            write_cr4(cr4 & ~X86_CR4_PGE);
-            barrier();
-            write_cr4(cr4);
-
-            post_flush(t);
-        }
+            do_tlb_flush();
     }
 
     if ( flags & FLUSH_CACHE )
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 6ce807bf6d..ceb31c2cd1 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -70,6 +70,11 @@ boolean_param("smep", opt_smep);
 static bool_t __initdata opt_smap = 1;
 boolean_param("smap", opt_smap);
 
+/* opt_invpcid: If false, don't use INVPCID instruction even if available. */
+static bool_t __initdata opt_invpcid = 1;
+boolean_param("invpcid", opt_invpcid);
+bool_t __read_mostly use_invpcid;
+
 unsigned long __read_mostly cr4_pv32_mask;
 
 /* Boot dom0 in pvh mode */
@@ -1424,6 +1429,9 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     if ( cpu_has_fsgsbase )
         set_in_cr4(X86_CR4_FSGSBASE);
 
+    if ( opt_invpcid && cpu_has_invpcid )
+        use_invpcid = 1;
+
     init_speculation_mitigations();
 
     init_idle_domain();
diff --git a/xen/include/asm-x86/invpcid.h b/xen/include/asm-x86/invpcid.h
index b46624a865..586beb7ab9 100644
--- a/xen/include/asm-x86/invpcid.h
+++ b/xen/include/asm-x86/invpcid.h
@@ -3,6 +3,8 @@
 
 #include <xen/types.h>
 
+extern bool_t use_invpcid;
+
 #define INVPCID_TYPE_INDIV_ADDR      0
 #define INVPCID_TYPE_SINGLE_CTXT     1
 #define INVPCID_TYPE_ALL_INCL_GLOBAL 2
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.7

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