x86/mm: Put MMU to hardware ASID translation in one place

hansendc · Ingo Molnar · commit dd95f1a4b5ca · 2017-12-22T20:13:04.000+01:00
There are effectively two ASID types:

 1. The one stored in the mmu_context that goes from 0..5
 2. The one programmed into the hardware that goes from 1..6

This consolidates the locations where converting between the two (by doing
a +1) to a single place which gives us a nice place to comment.
PAGE_TABLE_ISOLATION will also need to, given an ASID, know which hardware
ASID to flush for the userspace mapping.

Signed-off-by: Dave Hansen &lt;dave.hansen@linux.intel.com&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Andy Lutomirski &lt;luto@kernel.org&gt;
Cc: Boris Ostrovsky &lt;boris.ostrovsky@oracle.com&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Brian Gerst &lt;brgerst@gmail.com&gt;
Cc: Dave Hansen &lt;dave.hansen@intel.com&gt;
Cc: David Laight &lt;David.Laight@aculab.com&gt;
Cc: Denys Vlasenko &lt;dvlasenk@redhat.com&gt;
Cc: Eduardo Valentin &lt;eduval@amazon.com&gt;
Cc: Greg KH &lt;gregkh@linuxfoundation.org&gt;
Cc: H. Peter Anvin &lt;hpa@zytor.com&gt;
Cc: Josh Poimboeuf &lt;jpoimboe@redhat.com&gt;
Cc: Juergen Gross &lt;jgross@suse.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Will Deacon &lt;will.deacon@arm.com&gt;
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
@@ -85,20 +85,26 @@ static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
  */
 #define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_ASID_BITS) - 2)
 
-/*
- * If PCID is on, ASID-aware code paths put the ASID+1 into the PCID bits.
- * This serves two purposes.  It prevents a nasty situation in which
- * PCID-unaware code saves CR3, loads some other value (with PCID == 0),
- * and then restores CR3, thus corrupting the TLB for ASID 0 if the saved
- * ASID was nonzero.  It also means that any bugs involving loading a
- * PCID-enabled CR3 with CR4.PCIDE off will trigger deterministically.
- */
+static inline u16 kern_pcid(u16 asid)
+{
+	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
+	/*
+	 * If PCID is on, ASID-aware code paths put the ASID+1 into the
+	 * PCID bits.  This serves two purposes.  It prevents a nasty
+	 * situation in which PCID-unaware code saves CR3, loads some other
+	 * value (with PCID == 0), and then restores CR3, thus corrupting
+	 * the TLB for ASID 0 if the saved ASID was nonzero.  It also means
+	 * that any bugs involving loading a PCID-enabled CR3 with
+	 * CR4.PCIDE off will trigger deterministically.
+	 */
+	return asid + 1;
+}
+
 struct pgd_t;
 static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
 {
 	if (static_cpu_has(X86_FEATURE_PCID)) {
-		VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
-		return __sme_pa(pgd) | (asid + 1);
+		return __sme_pa(pgd) | kern_pcid(asid);
 	} else {
 		VM_WARN_ON_ONCE(asid != 0);
 		return __sme_pa(pgd);
@@ -108,7 +114,8 @@ static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
 static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
 {
 	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
-	return __sme_pa(pgd) | (asid + 1) | CR3_NOFLUSH;
+	VM_WARN_ON_ONCE(!this_cpu_has(X86_FEATURE_PCID));
+	return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
 }
 
 #ifdef CONFIG_PARAVIRT
