diff options
Diffstat (limited to 'arch/x86/include/asm/tlbflush.h')
| -rw-r--r-- | arch/x86/include/asm/tlbflush.h | 208 |
1 files changed, 175 insertions, 33 deletions
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index e1884cf35257..4a08dd2ab32a 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -10,38 +10,90 @@ #include <asm/special_insns.h> #include <asm/smp.h> #include <asm/invpcid.h> +#include <asm/pti.h> +#include <asm/processor-flags.h> -static inline u64 inc_mm_tlb_gen(struct mm_struct *mm) -{ - /* - * Bump the generation count. This also serves as a full barrier - * that synchronizes with switch_mm(): callers are required to order - * their read of mm_cpumask after their writes to the paging - * structures. - */ - return atomic64_inc_return(&mm->context.tlb_gen); -} +/* + * 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 */ -#define PTI_CONSUMED_ASID_BITS 0 +#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) -#define CR3_AVAIL_ASID_BITS (CR3_HW_ASID_BITS - PTI_CONSUMED_ASID_BITS) /* * ASIDs are zero-based: 0->MAX_AVAIL_ASID are valid. -1 below to account - * for them being zero-based. Another -1 is because ASID 0 is reserved for + * 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_ASID_BITS) - 2) +#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_SWITCH_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_SWITCH_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 @@ -53,6 +105,18 @@ static inline u16 kern_pcid(u16 asid) 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_SWITCH_BIT; +#endif + return ret; +} + struct pgd_t; static inline unsigned long build_cr3(pgd_t *pgd, u16 asid) { @@ -95,12 +159,6 @@ static inline bool tlb_defer_switch_to_init_mm(void) return !static_cpu_has(X86_FEATURE_PCID); } -/* - * 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; @@ -135,6 +193,24 @@ struct tlb_state { bool is_lazy; /* + * If set we changed the page tables in such a way that we + * needed an invalidation of all contexts (aka. PCIDs / ASIDs). + * This tells us to go invalidate all the non-loaded ctxs[] + * on the next context switch. + * + * The current ctx was kept up-to-date as it ran and does not + * need to be invalidated. + */ + bool invalidate_other; + + /* + * Mask that contains TLB_NR_DYN_ASIDS+1 bits to indicate + * the corresponding user PCID needs a flush next time we + * switch to it; see SWITCH_TO_USER_CR3. + */ + unsigned short user_pcid_flush_mask; + + /* * Access to this CR4 shadow and to H/W CR4 is protected by * disabling interrupts when modifying either one. */ @@ -215,6 +291,14 @@ static inline unsigned long cr4_read_shadow(void) } /* + * Mark all other ASIDs as invalid, preserves the current. + */ +static inline void invalidate_other_asid(void) +{ + this_cpu_write(cpu_tlbstate.invalidate_other, true); +} + +/* * Save some of cr4 feature set we're using (e.g. Pentium 4MB * enable and PPro Global page enable), so that any CPU's that boot * up after us can get the correct flags. This should only be used @@ -234,18 +318,47 @@ static inline void cr4_set_bits_and_update_boot(unsigned long mask) extern void initialize_tlbstate_and_flush(void); /* + * Given an ASID, flush the corresponding user ASID. We can delay this + * until the next time we switch to it. + * + * See SWITCH_TO_USER_CR3. + */ +static inline void invalidate_user_asid(u16 asid) +{ + /* There is no user ASID if address space separation is off */ + if (!IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION)) + return; + + /* + * We only have a single ASID if PCID is off and the CR3 + * write will have flushed it. + */ + if (!cpu_feature_enabled(X86_FEATURE_PCID)) + return; + + if (!static_cpu_has(X86_FEATURE_PTI)) + return; + + __set_bit(kern_pcid(asid), + (unsigned long *)this_cpu_ptr(&cpu_tlbstate.user_pcid_flush_mask)); +} + +/* * flush the entire current user mapping */ static inline void __native_flush_tlb(void) { /* - * If current->mm == NULL then we borrow a mm which may change during a - * task switch and therefore we must not be preempted while we write CR3 - * back: + * Preemption or interrupts must be disabled to protect the access + * to the per CPU variable and to prevent being preempted between + * read_cr3() and write_cr3(). */ - preempt_disable(); + WARN_ON_ONCE(preemptible()); + + invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid)); + + /* If current->mm == NULL then the read_cr3() "borrows" an mm */ native_write_cr3(__native_read_cr3()); - preempt_enable(); } /* @@ -259,6 +372,8 @@ static inline void __native_flush_tlb_global(void) /* * Using INVPCID is considerably faster than a pair of writes * to CR4 sandwiched inside an IRQ flag save/restore. + * + * Note, this works with CR4.PCIDE=0 or 1. */ invpcid_flush_all(); return; @@ -285,7 +400,21 @@ static inline void __native_flush_tlb_global(void) */ static inline void __native_flush_tlb_single(unsigned long addr) { + u32 loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid); + asm volatile("invlpg (%0)" ::"r" (addr) : "memory"); + + if (!static_cpu_has(X86_FEATURE_PTI)) + return; + + /* + * Some platforms #GP if we call invpcid(type=1/2) before CR4.PCIDE=1. + * Just use invalidate_user_asid() in case we are called early. + */ + if (!this_cpu_has(X86_FEATURE_INVPCID_SINGLE)) + invalidate_user_asid(loaded_mm_asid); + else + invpcid_flush_one(user_pcid(loaded_mm_asid), addr); } /* @@ -301,14 +430,6 @@ static inline void __flush_tlb_all(void) */ __flush_tlb(); } - - /* - * Note: if we somehow had PCID but not PGE, then this wouldn't work -- - * we'd end up flushing kernel translations for the current ASID but - * we might fail to flush kernel translations for other cached ASIDs. - * - * To avoid this issue, we force PCID off if PGE is off. - */ } /* @@ -318,6 +439,16 @@ static inline void __flush_tlb_one(unsigned long addr) { count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE); __flush_tlb_single(addr); + + if (!static_cpu_has(X86_FEATURE_PTI)) + return; + + /* + * __flush_tlb_single() will have cleared the TLB entry for this ASID, + * but since kernel space is replicated across all, we must also + * invalidate all others. + */ + invalidate_other_asid(); } #define TLB_FLUSH_ALL -1UL @@ -378,6 +509,17 @@ static inline void flush_tlb_page(struct vm_area_struct *vma, unsigned long a) void native_flush_tlb_others(const struct cpumask *cpumask, const struct flush_tlb_info *info); +static inline u64 inc_mm_tlb_gen(struct mm_struct *mm) +{ + /* + * Bump the generation count. This also serves as a full barrier + * that synchronizes with switch_mm(): callers are required to order + * their read of mm_cpumask after their writes to the paging + * structures. + */ + return atomic64_inc_return(&mm->context.tlb_gen); +} + static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch, struct mm_struct *mm) { |