x86/mm: Factor out CR3-building code

Current, the code that assembles a value to load into CR3 is
open-coded everywhere.  Factor it out into helpers build_cr3() and
build_cr3_noflush().

This makes one semantic change: __get_current_cr3_fast() was wrong
on SME systems.  No one noticed because the only caller is in the
VMX code, and there are no CPUs with both SME and VMX.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <Thomas.Lendacky@amd.com>
Link: http://lkml.kernel.org/r/ce350cf11e93e2842d14d0b95b0199c7d881f527.1505663533.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 1ab3821..93fe97c 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -126,8 +126,7 @@
 	 * isn't free.
 	 */
 #ifdef CONFIG_DEBUG_VM
-	if (WARN_ON_ONCE(__read_cr3() !=
-			 (__sme_pa(real_prev->pgd) | prev_asid))) {
+	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev, 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.
@@ -172,7 +171,7 @@
 			 */
 			this_cpu_write(cpu_tlbstate.ctxs[prev_asid].tlb_gen,
 				       next_tlb_gen);
-			write_cr3(__sme_pa(next->pgd) | prev_asid);
+			write_cr3(build_cr3(next, prev_asid));
 			trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH,
 					TLB_FLUSH_ALL);
 		}
@@ -216,12 +215,12 @@
 		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(__sme_pa(next->pgd) | new_asid);
+			write_cr3(build_cr3(next, new_asid));
 			trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH,
 					TLB_FLUSH_ALL);
 		} else {
 			/* The new ASID is already up to date. */
-			write_cr3(__sme_pa(next->pgd) | new_asid | CR3_NOFLUSH);
+			write_cr3(build_cr3_noflush(next, new_asid));
 			trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, 0);
 		}
 
@@ -265,7 +264,7 @@
 		!(cr4_read_shadow() & X86_CR4_PCIDE));
 
 	/* Force ASID 0 and force a TLB flush. */
-	write_cr3(cr3 & ~CR3_PCID_MASK);
+	write_cr3(build_cr3(mm, 0));
 
 	/* Reinitialize tlbstate. */
 	this_cpu_write(cpu_tlbstate.loaded_mm_asid, 0);