x86/mm: Handle LAM on context switch

Linear Address Masking mode for userspace pointers encoded in CR3 bits.
The mode is selected per-process and stored in mm_context_t.

switch_mm_irqs_off() now respects selected LAM mode and constructs CR3
accordingly.

The active LAM mode gets recorded in the tlb_state.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Alexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/all/20230312112612.31869-5-kirill.shutemov%40linux.intel.com

1 files changed, 37 insertions, 16 deletions

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 92d73ccede70..724f98d0e10f 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -154,26 +154,30 @@ static inline u16 user_pcid(u16 asid)
 	return ret;
 }
 
-static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
+static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, unsigned long lam)
 {
+	unsigned long cr3 = __sme_pa(pgd) | lam;
+
 	if (static_cpu_has(X86_FEATURE_PCID)) {
-		return __sme_pa(pgd) | kern_pcid(asid);
+		VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
+		cr3 |= kern_pcid(asid);
 	} else {
 		VM_WARN_ON_ONCE(asid != 0);
-		return __sme_pa(pgd);
 	}
+
+	return cr3;
 }
 
-static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
+static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid,
+					      unsigned long lam)
 {
-	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;
+	return build_cr3(pgd, asid, lam) | CR3_NOFLUSH;
 }
 
 /*
@@ -274,15 +278,16 @@ static inline void invalidate_user_asid(u16 asid)
 		  (unsigned long *)this_cpu_ptr(&cpu_tlbstate.user_pcid_flush_mask));
 }
 
-static void load_new_mm_cr3(pgd_t *pgdir, u16 new_asid, bool need_flush)
+static void load_new_mm_cr3(pgd_t *pgdir, u16 new_asid, unsigned long lam,
+			    bool need_flush)
 {
 	unsigned long new_mm_cr3;
 
 	if (need_flush) {
 		invalidate_user_asid(new_asid);
-		new_mm_cr3 = build_cr3(pgdir, new_asid);
+		new_mm_cr3 = build_cr3(pgdir, new_asid, lam);
 	} else {
-		new_mm_cr3 = build_cr3_noflush(pgdir, new_asid);
+		new_mm_cr3 = build_cr3_noflush(pgdir, new_asid, lam);
 	}
 
 	/*
@@ -491,6 +496,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 {
 	struct mm_struct *real_prev = this_cpu_read(cpu_tlbstate.loaded_mm);
 	u16 prev_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+	unsigned long new_lam = mm_lam_cr3_mask(next);
 	bool was_lazy = this_cpu_read(cpu_tlbstate_shared.is_lazy);
 	unsigned cpu = smp_processor_id();
 	u64 next_tlb_gen;
@@ -520,7 +526,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 	 * isn't free.
 	 */
 #ifdef CONFIG_DEBUG_VM
-	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev->pgd, prev_asid))) {
+	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev->pgd, prev_asid,
+						   tlbstate_lam_cr3_mask()))) {
 		/*
 		 * If we were to BUG here, we'd be very likely to kill
 		 * the system so hard that we don't see the call trace.
@@ -552,10 +559,16 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 	 * instruction.
 	 */
 	if (real_prev == next) {
+		/* Not actually switching mm's */
 		VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) !=
 			   next->context.ctx_id);
 
 		/*
+		 * If this races with another thread that enables lam, 'new_lam'
+		 * might not match tlbstate_lam_cr3_mask().
+		 */
+
+		/*
 		 * Even in lazy TLB mode, the CPU should stay set in the
 		 * mm_cpumask. The TLB shootdown code can figure out from
 		 * cpu_tlbstate_shared.is_lazy whether or not to send an IPI.
@@ -622,15 +635,16 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 		barrier();
 	}
 
+	set_tlbstate_lam_mode(next);
 	if (need_flush) {
 		this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id);
 		this_cpu_write(cpu_tlbstate.ctxs[new_asid].tlb_gen, next_tlb_gen);
-		load_new_mm_cr3(next->pgd, new_asid, true);
+		load_new_mm_cr3(next->pgd, new_asid, new_lam, true);
 
 		trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
 	} else {
 		/* The new ASID is already up to date. */
-		load_new_mm_cr3(next->pgd, new_asid, false);
+		load_new_mm_cr3(next->pgd, new_asid, new_lam, false);
 
 		trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, 0);
 	}
@@ -691,6 +705,10 @@ void initialize_tlbstate_and_flush(void)
 	/* Assert that CR3 already references the right mm. */
 	WARN_ON((cr3 & CR3_ADDR_MASK) != __pa(mm->pgd));
 
+	/* LAM expected to be disabled */
+	WARN_ON(cr3 & (X86_CR3_LAM_U48 | X86_CR3_LAM_U57));
+	WARN_ON(mm_lam_cr3_mask(mm));
+
 	/*
 	 * Assert that CR4.PCIDE is set if needed.  (CR4.PCIDE initialization
 	 * doesn't work like other CR4 bits because it can only be set from
@@ -699,8 +717,8 @@ void initialize_tlbstate_and_flush(void)
 	WARN_ON(boot_cpu_has(X86_FEATURE_PCID) &&
 		!(cr4_read_shadow() & X86_CR4_PCIDE));
 
-	/* Force ASID 0 and force a TLB flush. */
-	write_cr3(build_cr3(mm->pgd, 0));
+	/* Disable LAM, force ASID 0 and force a TLB flush. */
+	write_cr3(build_cr3(mm->pgd, 0, 0));
 
 	/* Reinitialize tlbstate. */
 	this_cpu_write(cpu_tlbstate.last_user_mm_spec, LAST_USER_MM_INIT);
@@ -708,6 +726,7 @@ void initialize_tlbstate_and_flush(void)
 	this_cpu_write(cpu_tlbstate.next_asid, 1);
 	this_cpu_write(cpu_tlbstate.ctxs[0].ctx_id, mm->context.ctx_id);
 	this_cpu_write(cpu_tlbstate.ctxs[0].tlb_gen, tlb_gen);
+	set_tlbstate_lam_mode(mm);
 
 	for (i = 1; i < TLB_NR_DYN_ASIDS; i++)
 		this_cpu_write(cpu_tlbstate.ctxs[i].ctx_id, 0);
@@ -1071,8 +1090,10 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end)
  */
 unsigned long __get_current_cr3_fast(void)
 {
-	unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
-		this_cpu_read(cpu_tlbstate.loaded_mm_asid));
+	unsigned long cr3 =
+		build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
+			  this_cpu_read(cpu_tlbstate.loaded_mm_asid),
+			  tlbstate_lam_cr3_mask());
 
 	/* For now, be very restrictive about when this can be called. */
 	VM_WARN_ON(in_nmi() || preemptible());