linux-kernel - [PATCH 4.14 27/74] x86/mm: Put MMU to hardware ASID translation in one place

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Date:   Wed, 27 Dec 2017 17:46:00 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        David Laight <David.Laight@...lab.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will.deacon@....com>, aliguori@...zon.com,
        daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com,
        linux-mm@...ck.org, Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.14 27/74] x86/mm: Put MMU to hardware ASID translation in one place

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Hansen <dave.hansen@...ux.intel.com>

commit dd95f1a4b5ca904c78e6a097091eb21436478abb upstream.

There are effectively two ASID types:

 1. The one stored in the mmu_context that goes from 0..5
 2. The one programmed into the hardware that goes from 1..6

This consolidates the locations where converting between the two (by doing
a +1) to a single place which gives us a nice place to comment.
PAGE_TABLE_ISOLATION will also need to, given an ASID, know which hardware
ASID to flush for the userspace mapping.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: David Laight <David.Laight@...lab.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Eduardo Valentin <eduval@...zon.com>
Cc: Greg KH <gregkh@...uxfoundation.org>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Will Deacon <will.deacon@....com>
Cc: aliguori@...zon.com
Cc: daniel.gruss@...k.tugraz.at
Cc: hughd@...gle.com
Cc: keescook@...gle.com
Cc: linux-mm@...ck.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/include/asm/tlbflush.h |   29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -85,20 +85,26 @@ static inline u64 inc_mm_tlb_gen(struct
  */
 #define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_ASID_BITS) - 2)
 
-/*
- * 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 u16 kern_pcid(u16 asid)
+{
+	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
+	/*
+	 * 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.
+	 */
+	return asid + 1;
+}
+
 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 > MAX_ASID_AVAILABLE);
-		return __sme_pa(pgd) | (asid + 1);
+		return __sme_pa(pgd) | kern_pcid(asid);
 	} else {
 		VM_WARN_ON_ONCE(asid != 0);
 		return __sme_pa(pgd);
@@ -108,7 +114,8 @@ static inline unsigned long build_cr3(pg
 static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
 {
 	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
-	return __sme_pa(pgd) | (asid + 1) | CR3_NOFLUSH;
+	VM_WARN_ON_ONCE(!this_cpu_has(X86_FEATURE_PCID));
+	return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
 }
 
 #ifdef CONFIG_PARAVIRT