From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
First, it's nice to remove the magic numbers.
Second, PAGE_TABLE_ISOLATION 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>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Eduardo Valentin <eduval@xxxxxxxxxx>
Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: aliguori@xxxxxxxxxx
Cc: daniel.gruss@xxxxxxxxxxxxxx
Cc: hughd@xxxxxxxxxx
Cc: keescook@xxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
---
arch/x86/include/asm/tlbflush.h | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -69,6 +69,22 @@ static inline u64 inc_mm_tlb_gen(struct
return atomic64_inc_return(&mm->context.tlb_gen);
}
+/* There are 12 bits of space for ASIDS in CR3 */
+#define CR3_HW_ASID_BITS 12
+/*
+ * When enabled, PAGE_TABLE_ISOLATION consumes a single bit for
+ * user/kernel switches
+ */
+#define PTI_CONSUMED_ASID_BITS 0
+
+#define CR3_AVAIL_ASID_BITS (CR3_HW_ASID_BITS - PTI_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 which
@@ -81,7 +97,7 @@ 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);
@@ -91,7 +107,7 @@ 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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