[PATCH 18/23] x86, mm: Move CR3 construction functions

[Dave Hansen]

For flushing the TLB, we need to know which ASID has been programmed
into the hardware.  Since that differs from what is in 'cpu_tlbstate',
we need to be able to transform the ASID in cpu_tlbstate to the one
programmed into the hardware.

It's not easy to include mmu_context.h into tlbflush.h, so just move
the CR3 building over to tlbflush.h.

Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Moritz Lipp <moritz.lipp@xxxxxxxxxxxxxx>
Cc: Daniel Gruss <daniel.gruss@xxxxxxxxxxxxxx>
Cc: Michael Schwarz <michael.schwarz@xxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
---

 b/arch/x86/include/asm/mmu_context.h |   29 +----------------------------
 b/arch/x86/include/asm/tlbflush.h    |   27 +++++++++++++++++++++++++++
 b/arch/x86/mm/tlb.c                  |    8 ++++----
 3 files changed, 32 insertions(+), 32 deletions(-)

diff -puN arch/x86/include/asm/mmu_context.h~kaiser-pcid-pre-build-func-move arch/x86/include/asm/mmu_context.h
--- a/arch/x86/include/asm/mmu_context.h~kaiser-pcid-pre-build-func-move	2017-10-31 15:03:58.508498981 -0700
+++ b/arch/x86/include/asm/mmu_context.h	2017-10-31 15:03:58.516499360 -0700
@@ -281,33 +281,6 @@ static inline bool arch_vma_access_permi
 }
 
 /*
- * 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.
- */
-
-static inline unsigned long build_cr3(struct mm_struct *mm, u16 asid)
-{
-	if (static_cpu_has(X86_FEATURE_PCID)) {
-		VM_WARN_ON_ONCE(asid > 4094);
-		return __sme_pa(mm->pgd) | (asid + 1);
-	} else {
-		VM_WARN_ON_ONCE(asid != 0);
-		return __sme_pa(mm->pgd);
-	}
-}
-
-static inline unsigned long build_cr3_noflush(struct mm_struct *mm, u16 asid)
-{
-	VM_WARN_ON_ONCE(asid > 4094);
-	return __sme_pa(mm->pgd) | (asid + 1) | CR3_NOFLUSH;
-}
-
-/*
  * This can be used from process context to figure out what the value of
  * CR3 is without needing to do a (slow) __read_cr3().
  *
@@ -316,7 +289,7 @@ static inline unsigned long build_cr3_no
  */
 static inline unsigned long __get_current_cr3_fast(void)
 {
-	unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm),
+	unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
 		this_cpu_read(cpu_tlbstate.loaded_mm_asid));
 
 	/* For now, be very restrictive about when this can be called. */
diff -puN arch/x86/include/asm/tlbflush.h~kaiser-pcid-pre-build-func-move arch/x86/include/asm/tlbflush.h
--- a/arch/x86/include/asm/tlbflush.h~kaiser-pcid-pre-build-func-move	2017-10-31 15:03:58.510499076 -0700
+++ b/arch/x86/include/asm/tlbflush.h	2017-10-31 15:03:58.518499454 -0700
@@ -74,6 +74,33 @@ static inline u64 inc_mm_tlb_gen(struct
 	return new_tlb_gen;
 }
 
+/*
+ * 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.
+ */
+struct pgd_t;
+static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
+{
+	if (static_cpu_has(X86_FEATURE_PCID)) {
+		VM_WARN_ON_ONCE(asid > 4094);
+		return __sme_pa(pgd) | (asid + 1);
+	} 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 > 4094);
+	return __sme_pa(pgd) | (asid + 1) | CR3_NOFLUSH;
+}
+
 #ifdef CONFIG_PARAVIRT
 #include <asm/paravirt.h>
 #else
diff -puN arch/x86/mm/tlb.c~kaiser-pcid-pre-build-func-move arch/x86/mm/tlb.c
--- a/arch/x86/mm/tlb.c~kaiser-pcid-pre-build-func-move	2017-10-31 15:03:58.512499170 -0700
+++ b/arch/x86/mm/tlb.c	2017-10-31 15:03:58.518499454 -0700
@@ -127,7 +127,7 @@ void switch_mm_irqs_off(struct mm_struct
 	 * isn't free.
 	 */
 #ifdef CONFIG_DEBUG_VM
-	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev, prev_asid))) {
+	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev->pgd, prev_asid))) {
 		/*
 		 * 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.
@@ -194,12 +194,12 @@ void switch_mm_irqs_off(struct mm_struct
 		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);
-			write_cr3(build_cr3(next, new_asid));
+			write_cr3(build_cr3(next->pgd, new_asid));
 			trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH,
 					TLB_FLUSH_ALL);
 		} else {
 			/* The new ASID is already up to date. */
-			write_cr3(build_cr3_noflush(next, new_asid));
+			write_cr3(build_cr3_noflush(next->pgd, new_asid));
 			trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, 0);
 		}
 
@@ -277,7 +277,7 @@ void initialize_tlbstate_and_flush(void)
 		!(cr4_read_shadow() & X86_CR4_PCIDE));
 
 	/* Force ASID 0 and force a TLB flush. */
-	write_cr3(build_cr3(mm, 0));
+	write_cr3(build_cr3(mm->pgd, 0));
 
 	/* Reinitialize tlbstate. */
 	this_cpu_write(cpu_tlbstate.loaded_mm_asid, 0);
_