x86/tlb: Move PCID helpers where they are used

Aside of the fact that they are used only in the TLB code, especially
having the comment close to the actual implementation makes a lot of
sense.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200421092600.145772183@linutronix.de

arch/x86/include/asm/tlbflush.h

@@ -13,133 +13,6 @@
 #include <asm/pti.h>
 #include <asm/processor-flags.h>
 
-/*
- * The x86 feature is called PCID (Process Context IDentifier). It is similar
- * to what is traditionally called ASID on the RISC processors.
- *
- * We don't use the traditional ASID implementation, where each process/mm gets
- * its own ASID and flush/restart when we run out of ASID space.
- *
- * Instead we have a small per-cpu array of ASIDs and cache the last few mm's
- * that came by on this CPU, allowing cheaper switch_mm between processes on
- * this CPU.
- *
- * We end up with different spaces for different things. To avoid confusion we
- * use different names for each of them:
- *
- * ASID  - [0, TLB_NR_DYN_ASIDS-1]
- *         the canonical identifier for an mm
- *
- * kPCID - [1, TLB_NR_DYN_ASIDS]
- *         the value we write into the PCID part of CR3; corresponds to the
- *         ASID+1, because PCID 0 is special.
- *
- * uPCID - [2048 + 1, 2048 + TLB_NR_DYN_ASIDS]
- *         for KPTI each mm has two address spaces and thus needs two
- *         PCID values, but we can still do with a single ASID denomination
- *         for each mm. Corresponds to kPCID + 2048.
- *
- */
-
-/* There are 12 bits of space for ASIDS in CR3 */
-#define CR3_HW_ASID_BITS		12
-
-/*
- * When enabled, PAGE_TABLE_ISOLATION consumes a single bit for
- * user/kernel switches
- */
-#ifdef CONFIG_PAGE_TABLE_ISOLATION
-# define PTI_CONSUMED_PCID_BITS	1
-#else
-# define PTI_CONSUMED_PCID_BITS	0
-#endif
-
-#define CR3_AVAIL_PCID_BITS (X86_CR3_PCID_BITS - PTI_CONSUMED_PCID_BITS)
-
-/*
- * ASIDs are zero-based: 0->MAX_AVAIL_ASID are valid.  -1 below to account
- * for them being zero-based.  Another -1 is because PCID 0 is reserved for
- * use by non-PCID-aware users.
- */
-#define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_PCID_BITS) - 2)
-
-/*
- * 6 because 6 should be plenty and struct tlb_state will fit in two cache
- * lines.
- */
-#define TLB_NR_DYN_ASIDS	6
-
-/*
- * Given @asid, compute kPCID
- */
-static inline u16 kern_pcid(u16 asid)
-{
-	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
-
-#ifdef CONFIG_PAGE_TABLE_ISOLATION
-	/*
-	 * Make sure that the dynamic ASID space does not confict with the
-	 * bit we are using to switch between user and kernel ASIDs.
-	 */
-	BUILD_BUG_ON(TLB_NR_DYN_ASIDS >= (1 << X86_CR3_PTI_PCID_USER_BIT));
-
-	/*
-	 * The ASID being passed in here should have respected the
-	 * MAX_ASID_AVAILABLE and thus never have the switch bit set.
-	 */
-	VM_WARN_ON_ONCE(asid & (1 << X86_CR3_PTI_PCID_USER_BIT));
-#endif
-	/*
-	 * The dynamically-assigned ASIDs that get passed in are small
-	 * (<TLB_NR_DYN_ASIDS).  They never have the high switch bit set,
-	 * so do not bother to clear it.
-	 *
-	 * 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;
-}
-
-/*
- * Given @asid, compute uPCID
- */
-static inline u16 user_pcid(u16 asid)
-{
-	u16 ret = kern_pcid(asid);
-#ifdef CONFIG_PAGE_TABLE_ISOLATION
-	ret |= 1 << X86_CR3_PTI_PCID_USER_BIT;
-#endif
-	return ret;
-}
-
-struct pgd_t;
-static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
-{
-	if (static_cpu_has(X86_FEATURE_PCID)) {
-		return __sme_pa(pgd) | kern_pcid(asid);
-	} else {
-		VM_WARN_ON_ONCE(asid != 0);
-		return __sme_pa(pgd);
-	}
-}
-
-static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
-{
-	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
-	/*
-	 * Use boot_cpu_has() instead of this_cpu_has() as this function
-	 * might be called during early boot. This should work even after
-	 * boot because all CPU's the have same capabilities:
-	 */
-	VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
-	return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
-}
-
 struct flush_tlb_info;
 
 void __flush_tlb_all(void);
@@ -153,6 +26,12 @@ void flush_tlb_others(const struct cpumask *cpumask,
 #include <asm/paravirt.h>
 #endif
 
+/*
+ * 6 because 6 should be plenty and struct tlb_state will fit in two cache
+ * lines.
+ */
+#define TLB_NR_DYN_ASIDS	6
+
 struct tlb_context {
 	u64 ctx_id;
 	u64 tlb_gen;

arch/x86/mm/tlb.c

@@ -48,6 +48,126 @@
  */
 #define LAST_USER_MM_IBPB	0x1UL
 
+/*
+ * The x86 feature is called PCID (Process Context IDentifier). It is similar
+ * to what is traditionally called ASID on the RISC processors.
+ *
+ * We don't use the traditional ASID implementation, where each process/mm gets
+ * its own ASID and flush/restart when we run out of ASID space.
+ *
+ * Instead we have a small per-cpu array of ASIDs and cache the last few mm's
+ * that came by on this CPU, allowing cheaper switch_mm between processes on
+ * this CPU.
+ *
+ * We end up with different spaces for different things. To avoid confusion we
+ * use different names for each of them:
+ *
+ * ASID  - [0, TLB_NR_DYN_ASIDS-1]
+ *         the canonical identifier for an mm
+ *
+ * kPCID - [1, TLB_NR_DYN_ASIDS]
+ *         the value we write into the PCID part of CR3; corresponds to the
+ *         ASID+1, because PCID 0 is special.
+ *
+ * uPCID - [2048 + 1, 2048 + TLB_NR_DYN_ASIDS]
+ *         for KPTI each mm has two address spaces and thus needs two
+ *         PCID values, but we can still do with a single ASID denomination
+ *         for each mm. Corresponds to kPCID + 2048.
+ *
+ */
+
+/* There are 12 bits of space for ASIDS in CR3 */
+#define CR3_HW_ASID_BITS		12
+
+/*
+ * When enabled, PAGE_TABLE_ISOLATION consumes a single bit for
+ * user/kernel switches
+ */
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+# define PTI_CONSUMED_PCID_BITS	1
+#else
+# define PTI_CONSUMED_PCID_BITS	0
+#endif
+
+#define CR3_AVAIL_PCID_BITS (X86_CR3_PCID_BITS - PTI_CONSUMED_PCID_BITS)
+
+/*
+ * ASIDs are zero-based: 0->MAX_AVAIL_ASID are valid.  -1 below to account
+ * for them being zero-based.  Another -1 is because PCID 0 is reserved for
+ * use by non-PCID-aware users.
+ */
+#define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_PCID_BITS) - 2)
+
+/*
+ * Given @asid, compute kPCID
+ */
+static inline u16 kern_pcid(u16 asid)
+{
+	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
+
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+	/*
+	 * Make sure that the dynamic ASID space does not confict with the
+	 * bit we are using to switch between user and kernel ASIDs.
+	 */
+	BUILD_BUG_ON(TLB_NR_DYN_ASIDS >= (1 << X86_CR3_PTI_PCID_USER_BIT));
+
+	/*
+	 * The ASID being passed in here should have respected the
+	 * MAX_ASID_AVAILABLE and thus never have the switch bit set.
+	 */
+	VM_WARN_ON_ONCE(asid & (1 << X86_CR3_PTI_PCID_USER_BIT));
+#endif
+	/*
+	 * The dynamically-assigned ASIDs that get passed in are small
+	 * (<TLB_NR_DYN_ASIDS).  They never have the high switch bit set,
+	 * so do not bother to clear it.
+	 *
+	 * 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;
+}
+
+/*
+ * Given @asid, compute uPCID
+ */
+static inline u16 user_pcid(u16 asid)
+{
+	u16 ret = kern_pcid(asid);
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+	ret |= 1 << X86_CR3_PTI_PCID_USER_BIT;
+#endif
+	return ret;
+}
+
+static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
+{
+	if (static_cpu_has(X86_FEATURE_PCID)) {
+		return __sme_pa(pgd) | kern_pcid(asid);
+	} else {
+		VM_WARN_ON_ONCE(asid != 0);
+		return __sme_pa(pgd);
+	}
+}
+
+static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
+{
+	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
+	/*
+	 * Use boot_cpu_has() instead of this_cpu_has() as this function
+	 * might be called during early boot. This should work even after
+	 * boot because all CPU's the have same capabilities:
+	 */
+	VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
+	return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
+}
+
 /*
  * We get here when we do something requiring a TLB invalidation
  * but could not go invalidate all of the contexts.  We do the