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@@ -10,38 +10,90 @@
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#include <asm/special_insns.h>
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#include <asm/smp.h>
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#include <asm/invpcid.h>
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+#include <asm/pti.h>
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+#include <asm/processor-flags.h>
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-static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
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-{
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- /*
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- * Bump the generation count. This also serves as a full barrier
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- * that synchronizes with switch_mm(): callers are required to order
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- * their read of mm_cpumask after their writes to the paging
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- * structures.
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- */
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- return atomic64_inc_return(&mm->context.tlb_gen);
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-}
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+/*
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+ * The x86 feature is called PCID (Process Context IDentifier). It is similar
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+ * to what is traditionally called ASID on the RISC processors.
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+ *
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+ * We don't use the traditional ASID implementation, where each process/mm gets
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+ * its own ASID and flush/restart when we run out of ASID space.
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+ *
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+ * Instead we have a small per-cpu array of ASIDs and cache the last few mm's
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+ * that came by on this CPU, allowing cheaper switch_mm between processes on
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+ * this CPU.
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+ *
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+ * We end up with different spaces for different things. To avoid confusion we
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+ * use different names for each of them:
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+ *
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+ * ASID - [0, TLB_NR_DYN_ASIDS-1]
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+ * the canonical identifier for an mm
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+ *
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+ * kPCID - [1, TLB_NR_DYN_ASIDS]
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+ * the value we write into the PCID part of CR3; corresponds to the
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+ * ASID+1, because PCID 0 is special.
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+ *
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+ * uPCID - [2048 + 1, 2048 + TLB_NR_DYN_ASIDS]
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+ * for KPTI each mm has two address spaces and thus needs two
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+ * PCID values, but we can still do with a single ASID denomination
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+ * for each mm. Corresponds to kPCID + 2048.
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+ *
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+ */
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/* There are 12 bits of space for ASIDS in CR3 */
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#define CR3_HW_ASID_BITS 12
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+
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/*
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* When enabled, PAGE_TABLE_ISOLATION consumes a single bit for
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* user/kernel switches
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*/
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-#define PTI_CONSUMED_ASID_BITS 0
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+#ifdef CONFIG_PAGE_TABLE_ISOLATION
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+# define PTI_CONSUMED_PCID_BITS 1
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+#else
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+# define PTI_CONSUMED_PCID_BITS 0
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+#endif
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+
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+#define CR3_AVAIL_PCID_BITS (X86_CR3_PCID_BITS - PTI_CONSUMED_PCID_BITS)
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-#define CR3_AVAIL_ASID_BITS (CR3_HW_ASID_BITS - PTI_CONSUMED_ASID_BITS)
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/*
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* ASIDs are zero-based: 0->MAX_AVAIL_ASID are valid. -1 below to account
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- * for them being zero-based. Another -1 is because ASID 0 is reserved for
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+ * for them being zero-based. Another -1 is because PCID 0 is reserved for
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* use by non-PCID-aware users.
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*/
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-#define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_ASID_BITS) - 2)
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+#define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_PCID_BITS) - 2)
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+
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+/*
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+ * 6 because 6 should be plenty and struct tlb_state will fit in two cache
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+ * lines.
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+ */
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+#define TLB_NR_DYN_ASIDS 6
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+/*
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+ * Given @asid, compute kPCID
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+ */
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static inline u16 kern_pcid(u16 asid)
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{
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VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
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+
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+#ifdef CONFIG_PAGE_TABLE_ISOLATION
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+ /*
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+ * Make sure that the dynamic ASID space does not confict with the
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+ * bit we are using to switch between user and kernel ASIDs.
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+ */
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+ BUILD_BUG_ON(TLB_NR_DYN_ASIDS >= (1 << X86_CR3_PTI_SWITCH_BIT));
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+
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/*
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+ * The ASID being passed in here should have respected the
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+ * MAX_ASID_AVAILABLE and thus never have the switch bit set.
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+ */
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+ VM_WARN_ON_ONCE(asid & (1 << X86_CR3_PTI_SWITCH_BIT));
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+#endif
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+ /*
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+ * The dynamically-assigned ASIDs that get passed in are small
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+ * (<TLB_NR_DYN_ASIDS). They never have the high switch bit set,
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+ * so do not bother to clear it.
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+ *
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* If PCID is on, ASID-aware code paths put the ASID+1 into the
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* PCID bits. This serves two purposes. It prevents a nasty
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* situation in which PCID-unaware code saves CR3, loads some other
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@@ -53,6 +105,18 @@ static inline u16 kern_pcid(u16 asid)
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return asid + 1;
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}
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+/*
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+ * Given @asid, compute uPCID
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+ */
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+static inline u16 user_pcid(u16 asid)
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+{
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+ u16 ret = kern_pcid(asid);
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+#ifdef CONFIG_PAGE_TABLE_ISOLATION
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+ ret |= 1 << X86_CR3_PTI_SWITCH_BIT;
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+#endif
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+ return ret;
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+}
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+
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struct pgd_t;
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static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
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{
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@@ -95,12 +159,6 @@ static inline bool tlb_defer_switch_to_init_mm(void)
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return !static_cpu_has(X86_FEATURE_PCID);
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}
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-/*
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- * 6 because 6 should be plenty and struct tlb_state will fit in
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- * two cache lines.
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- */
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-#define TLB_NR_DYN_ASIDS 6
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-
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struct tlb_context {
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u64 ctx_id;
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u64 tlb_gen;
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@@ -134,6 +192,24 @@ struct tlb_state {
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*/
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bool is_lazy;
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+ /*
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+ * If set we changed the page tables in such a way that we
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+ * needed an invalidation of all contexts (aka. PCIDs / ASIDs).
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+ * This tells us to go invalidate all the non-loaded ctxs[]
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+ * on the next context switch.
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+ *
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+ * The current ctx was kept up-to-date as it ran and does not
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+ * need to be invalidated.
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+ */
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+ bool invalidate_other;
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+
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+ /*
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+ * Mask that contains TLB_NR_DYN_ASIDS+1 bits to indicate
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+ * the corresponding user PCID needs a flush next time we
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+ * switch to it; see SWITCH_TO_USER_CR3.
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+ */
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+ unsigned short user_pcid_flush_mask;
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+
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/*
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* Access to this CR4 shadow and to H/W CR4 is protected by
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* disabling interrupts when modifying either one.
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@@ -214,6 +290,14 @@ static inline unsigned long cr4_read_shadow(void)
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return this_cpu_read(cpu_tlbstate.cr4);
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}
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+/*
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+ * Mark all other ASIDs as invalid, preserves the current.
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+ */
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+static inline void invalidate_other_asid(void)
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+{
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+ this_cpu_write(cpu_tlbstate.invalidate_other, true);
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+}
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+
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/*
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* Save some of cr4 feature set we're using (e.g. Pentium 4MB
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* enable and PPro Global page enable), so that any CPU's that boot
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@@ -233,19 +317,48 @@ static inline void cr4_set_bits_and_update_boot(unsigned long mask)
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extern void initialize_tlbstate_and_flush(void);
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+/*
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+ * Given an ASID, flush the corresponding user ASID. We can delay this
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+ * until the next time we switch to it.
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+ *
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+ * See SWITCH_TO_USER_CR3.
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+ */
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+static inline void invalidate_user_asid(u16 asid)
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+{
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+ /* There is no user ASID if address space separation is off */
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+ if (!IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION))
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+ return;
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+
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+ /*
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+ * We only have a single ASID if PCID is off and the CR3
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+ * write will have flushed it.
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+ */
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+ if (!cpu_feature_enabled(X86_FEATURE_PCID))
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+ return;
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+
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+ if (!static_cpu_has(X86_FEATURE_PTI))
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+ return;
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+
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+ __set_bit(kern_pcid(asid),
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+ (unsigned long *)this_cpu_ptr(&cpu_tlbstate.user_pcid_flush_mask));
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+}
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+
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/*
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* flush the entire current user mapping
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*/
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static inline void __native_flush_tlb(void)
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{
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/*
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- * If current->mm == NULL then we borrow a mm which may change during a
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- * task switch and therefore we must not be preempted while we write CR3
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- * back:
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+ * Preemption or interrupts must be disabled to protect the access
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+ * to the per CPU variable and to prevent being preempted between
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+ * read_cr3() and write_cr3().
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*/
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- preempt_disable();
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+ WARN_ON_ONCE(preemptible());
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+
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+ invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
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+
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+ /* If current->mm == NULL then the read_cr3() "borrows" an mm */
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native_write_cr3(__native_read_cr3());
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- preempt_enable();
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}
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/*
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@@ -259,6 +372,8 @@ static inline void __native_flush_tlb_global(void)
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/*
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* Using INVPCID is considerably faster than a pair of writes
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* to CR4 sandwiched inside an IRQ flag save/restore.
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+ *
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+ * Note, this works with CR4.PCIDE=0 or 1.
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*/
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invpcid_flush_all();
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return;
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@@ -285,7 +400,21 @@ static inline void __native_flush_tlb_global(void)
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*/
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static inline void __native_flush_tlb_single(unsigned long addr)
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{
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+ u32 loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
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+
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asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
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+
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+ if (!static_cpu_has(X86_FEATURE_PTI))
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+ return;
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+
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+ /*
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+ * Some platforms #GP if we call invpcid(type=1/2) before CR4.PCIDE=1.
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+ * Just use invalidate_user_asid() in case we are called early.
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+ */
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+ if (!this_cpu_has(X86_FEATURE_INVPCID_SINGLE))
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+ invalidate_user_asid(loaded_mm_asid);
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+ else
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+ invpcid_flush_one(user_pcid(loaded_mm_asid), addr);
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}
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/*
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@@ -301,14 +430,6 @@ static inline void __flush_tlb_all(void)
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*/
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__flush_tlb();
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}
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-
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- /*
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- * Note: if we somehow had PCID but not PGE, then this wouldn't work --
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- * we'd end up flushing kernel translations for the current ASID but
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- * we might fail to flush kernel translations for other cached ASIDs.
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- *
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- * To avoid this issue, we force PCID off if PGE is off.
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- */
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}
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/*
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@@ -318,6 +439,16 @@ static inline void __flush_tlb_one(unsigned long addr)
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{
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count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE);
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__flush_tlb_single(addr);
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+
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+ if (!static_cpu_has(X86_FEATURE_PTI))
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+ return;
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+
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+ /*
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+ * __flush_tlb_single() will have cleared the TLB entry for this ASID,
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+ * but since kernel space is replicated across all, we must also
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+ * invalidate all others.
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+ */
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+ invalidate_other_asid();
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}
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#define TLB_FLUSH_ALL -1UL
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@@ -378,6 +509,17 @@ static inline void flush_tlb_page(struct vm_area_struct *vma, unsigned long a)
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void native_flush_tlb_others(const struct cpumask *cpumask,
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const struct flush_tlb_info *info);
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+static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
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+{
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+ /*
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+ * Bump the generation count. This also serves as a full barrier
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+ * that synchronizes with switch_mm(): callers are required to order
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+ * their read of mm_cpumask after their writes to the paging
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+ * structures.
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+ */
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+ return atomic64_inc_return(&mm->context.tlb_gen);
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+}
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+
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static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch,
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struct mm_struct *mm)
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{
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