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Subject[patch 50/60] x86/mm: Put MMU to hardware ASID translation in one place
From: Dave Hansen <dave.hansen@linux.intel.com>

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.
KERNEL_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@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: keescook@google.com
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: moritz.lipp@iaik.tugraz.at
Cc: linux-mm@kvack.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: hughd@google.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: michael.schwarz@iaik.tugraz.at
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: richard.fellner@student.tugraz.at
Link: https://lkml.kernel.org/r/20171123003506.67E81D7F@viggo.jf.intel.com

---
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
@@ -91,20 +91,26 @@ 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);
@@ -114,7 +120,8 @@ 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

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