From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
First, it's nice to remove the magic numbers.
Second, KAISER is going to consume half of the available ASID
space. The space is currently unused, but add a comment to spell
out this new restriction.
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: Richard Fellner <richard.fellner@xxxxxxxxxxxxxxxxx>
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/tlbflush.h | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff -puN arch/x86/include/asm/tlbflush.h~kaiser-pcid-pre-build-asids-macros arch/x86/include/asm/tlbflush.h
--- a/arch/x86/include/asm/tlbflush.h~kaiser-pcid-pre-build-asids-macros 2017-11-22 15:45:51.814619732 -0800
+++ b/arch/x86/include/asm/tlbflush.h 2017-11-22 15:45:51.818619732 -0800
@@ -75,6 +75,19 @@ static inline u64 inc_mm_tlb_gen(struct
return new_tlb_gen;
}
+/* There are 12 bits of space for ASIDS in CR3 */
+#define CR3_HW_ASID_BITS 12
+/* When enabled, KAISER consumes a single bit for user/kernel switches */
+#define KAISER_CONSUMED_ASID_BITS 0
+
+#define CR3_AVAIL_ASID_BITS (CR3_HW_ASID_BITS - KAISER_CONSUMED_ASID_BITS)
+/*
+ * ASIDs are zero-based: 0->MAX_AVAIL_ASID are valid. -1 below
+ * to account for them being zero-based. Another -1 is because ASID 0
+ * is reserved for use by non-PCID-aware users.
+ */
+#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
@@ -88,7 +101,7 @@ 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);
+ VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
return __sme_pa(pgd) | (asid + 1);
} else {
VM_WARN_ON_ONCE(asid != 0);
@@ -98,7 +111,7 @@ static inline unsigned long build_cr3(pg
static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
{
- VM_WARN_ON_ONCE(asid > 4094);
+ VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
return __sme_pa(pgd) | (asid + 1) | CR3_NOFLUSH;
}
_
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