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Subject[patch V2 14/16] x86/tlb: Move PCID helpers where they are used
Aside of the fact that they are only used 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>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/tlbflush.h | 133 +---------------------------------------
arch/x86/mm/tlb.c | 120 ++++++++++++++++++++++++++++++++++++
2 files changed, 126 insertions(+), 127 deletions(-)

--- a/arch/x86/include/asm/tlbflush.h
+++ b/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 cpuma
#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;
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -49,6 +49,126 @@
#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
* necessary invalidation by clearing out the 'ctx_id' which
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