linux-kernel - [PATCH 1/4] x86/mm: Factor out CR3-building code

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Message-Id: <ce350cf11e93e2842d14d0b95b0199c7d881f527.1505663533.git.luto@kernel.org>
Date:   Sun, 17 Sep 2017 09:03:48 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     X86 ML <x86@...nel.org>
Cc:     Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Tom Lendacky <Thomas.Lendacky@....com>
Subject: [PATCH 1/4] 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.

Cc: Tom Lendacky <Thomas.Lendacky@....com>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/include/asm/mmu_context.h | 15 +++++++++++----
 arch/x86/mm/tlb.c                  | 11 +++++------
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 7ae318c340d9..a999ba6b721f 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -286,6 +286,15 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
 	return __pkru_allows_pkey(vma_pkey(vma), write);
 }
 
+static inline unsigned long build_cr3(struct mm_struct *mm, u16 asid)
+{
+	return __sme_pa(mm->pgd) | asid;
+}
+
+static inline unsigned long build_cr3_noflush(struct mm_struct *mm, u16 asid)
+{
+	return __sme_pa(mm->pgd) | asid | CR3_NOFLUSH;
+}
 
 /*
  * This can be used from process context to figure out what the value of
@@ -296,10 +305,8 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
  */
 static inline unsigned long __get_current_cr3_fast(void)
 {
-	unsigned long cr3 = __pa(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd);
-
-	if (static_cpu_has(X86_FEATURE_PCID))
-		cr3 |= this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+	unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm),
+		this_cpu_read(cpu_tlbstate.loaded_mm_asid));
 
 	/* For now, be very restrictive about when this can be called. */
 	VM_WARN_ON(in_nmi() || preemptible());
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 1ab3821f9e26..93fe97cce581 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -126,8 +126,7 @@ 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() !=
-			 (__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 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 			 */
 			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 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *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);
-			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 @@ void initialize_tlbstate_and_flush(void)
 		!(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);
-- 
2.13.5