[SPARC64]: Move away from virtual page tables, part 1.

We now use the TSB hardware assist features of the UltraSPARC
MMUs.

SMP is currently knowingly broken, we need to find another place
to store the per-cpu base pointers.  We hid them away in the TSB
base register, and that obviously will not work any more :-)

Another known broken case is non-8KB base page size.

Also noticed that flush_tlb_all() is not referenced anywhere, only
the internal __flush_tlb_all() (local cpu only) is used by the
sparc64 port, so we can get rid of flush_tlb_all().

The kernel gets it's own 8KB TSB (swapper_tsb) and each address space
gets it's own private 8K TSB.  Later we can add code to dynamically
increase the size of per-process TSB as the RSS grows.  An 8KB TSB is
good enough for up to about a 4MB RSS, after which the TSB starts to
incur many capacity and conflict misses.

We even accumulate OBP translations into the kernel TSB.

Another area for refinement is large page size support.  We could use
a secondary address space TSB to handle those.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 165 insertions, 0 deletions

diff --git a/include/asm-sparc64/tsb.h b/include/asm-sparc64/tsb.h
new file mode 100644
index 0000000..03d272e
--- /dev/null
+++ b/include/asm-sparc64/tsb.h
@@ -0,0 +1,165 @@
+#ifndef _SPARC64_TSB_H
+#define _SPARC64_TSB_H
+
+/* The sparc64 TSB is similar to the powerpc hashtables.  It's a
+ * power-of-2 sized table of TAG/PTE pairs.  The cpu precomputes
+ * pointers into this table for 8K and 64K page sizes, and also a
+ * comparison TAG based upon the virtual address and context which
+ * faults.
+ *
+ * TLB miss trap handler software does the actual lookup via something
+ * of the form:
+ *
+ * 	ldxa		[%g0] ASI_{D,I}MMU_TSB_8KB_PTR, %g1
+ * 	ldxa		[%g0] ASI_{D,I}MMU, %g6
+ * 	ldda		[%g1] ASI_NUCLEUS_QUAD_LDD, %g4
+ * 	cmp		%g4, %g6
+ * 	bne,pn	%xcc, tsb_miss_{d,i}tlb
+ * 	 mov		FAULT_CODE_{D,I}TLB, %g3
+ * 	stxa		%g5, [%g0] ASI_{D,I}TLB_DATA_IN
+ * 	retry
+ *
+
+ * Each 16-byte slot of the TSB is the 8-byte tag and then the 8-byte
+ * PTE.  The TAG is of the same layout as the TLB TAG TARGET mmu
+ * register which is:
+ *
+ * -------------------------------------------------
+ * |  -  |  CONTEXT |  -  |    VADDR bits 63:22    |
+ * -------------------------------------------------
+ *  63 61 60      48 47 42 41                     0
+ *
+ * Like the powerpc hashtables we need to use locking in order to
+ * synchronize while we update the entries.  PTE updates need locking
+ * as well.
+ *
+ * We need to carefully choose a lock bits for the TSB entry.  We
+ * choose to use bit 47 in the tag.  Also, since we never map anything
+ * at page zero in context zero, we use zero as an invalid tag entry.
+ * When the lock bit is set, this forces a tag comparison failure.
+ *
+ * Currently, we allocate an 8K TSB per-process and we use it for both
+ * I-TLB and D-TLB misses.  Perhaps at some point we'll add code that
+ * monitors the number of active pages in the process as we get
+ * major/minor faults, and grow the TSB in response.  The only trick
+ * in implementing that is synchronizing the freeing of the old TSB
+ * wrt.  parallel TSB updates occuring on other processors.  On
+ * possible solution is to use RCU for the freeing of the TSB.
+ */
+
+#define TSB_TAG_LOCK	(1 << (47 - 32))
+
+#define TSB_MEMBAR	membar	#StoreStore
+
+#define TSB_LOCK_TAG(TSB, REG1, REG2)	\
+99:	lduwa	[TSB] ASI_N, REG1;	\
+	sethi	%hi(TSB_TAG_LOCK), REG2;\
+	andcc	REG1, REG2, %g0;	\
+	bne,pn	%icc, 99b;		\
+	 nop;				\
+	casa	[TSB] ASI_N, REG1, REG2;\
+	cmp	REG1, REG2;		\
+	bne,pn	%icc, 99b;		\
+	 nop;				\
+	TSB_MEMBAR
+
+#define TSB_WRITE(TSB, TTE, TAG)	   \
+	stx		TTE, [TSB + 0x08]; \
+	TSB_MEMBAR;			   \
+	stx		TAG, [TSB + 0x00];
+
+	/* Do a kernel page table walk.  Leaves physical PTE pointer in
+	 * REG1.  Jumps to FAIL_LABEL on early page table walk termination.
+	 * VADDR will not be clobbered, but REG2 will.
+	 */
+#define KERN_PGTABLE_WALK(VADDR, REG1, REG2, FAIL_LABEL)	\
+	sethi		%hi(swapper_pg_dir), REG1; \
+	or		REG1, %lo(swapper_pg_dir), REG1; \
+	sllx		VADDR, 64 - (PGDIR_SHIFT + PGDIR_BITS), REG2; \
+	srlx		REG2, 64 - PAGE_SHIFT, REG2; \
+	andn		REG2, 0x3, REG2; \
+	lduw		[REG1 + REG2], REG1; \
+	brz,pn		REG1, FAIL_LABEL; \
+	 sllx		VADDR, 64 - (PMD_SHIFT + PMD_BITS), REG2; \
+	srlx		REG2, 64 - PAGE_SHIFT, REG2; \
+	sllx		REG1, 11, REG1; \
+	andn		REG2, 0x3, REG2; \
+	lduwa		[REG1 + REG2] ASI_PHYS_USE_EC, REG1; \
+	brz,pn		REG1, FAIL_LABEL; \
+	 sllx		VADDR, 64 - PMD_SHIFT, REG2; \
+	srlx		REG2, 64 - PAGE_SHIFT, REG2; \
+	sllx		REG1, 11, REG1; \
+	andn		REG2, 0x7, REG2; \
+	add		REG1, REG2, REG1;
+
+	/* Do a user page table walk in MMU globals.  Leaves physical PTE
+	 * pointer in REG1.  Jumps to FAIL_LABEL on early page table walk
+	 * termination.  Physical base of page tables is in PHYS_PGD which
+	 * will not be modified.
+	 *
+	 * VADDR will not be clobbered, but REG1 and REG2 will.
+	 */
+#define USER_PGTABLE_WALK_TL1(VADDR, PHYS_PGD, REG1, REG2, FAIL_LABEL)	\
+	sllx		VADDR, 64 - (PGDIR_SHIFT + PGDIR_BITS), REG2; \
+	srlx		REG2, 64 - PAGE_SHIFT, REG2; \
+	andn		REG2, 0x3, REG2; \
+	lduwa		[PHYS_PGD + REG2] ASI_PHYS_USE_EC, REG1; \
+	brz,pn		REG1, FAIL_LABEL; \
+	 sllx		VADDR, 64 - (PMD_SHIFT + PMD_BITS), REG2; \
+	srlx		REG2, 64 - PAGE_SHIFT, REG2; \
+	sllx		REG1, 11, REG1; \
+	andn		REG2, 0x3, REG2; \
+	lduwa		[REG1 + REG2] ASI_PHYS_USE_EC, REG1; \
+	brz,pn		REG1, FAIL_LABEL; \
+	 sllx		VADDR, 64 - PMD_SHIFT, REG2; \
+	srlx		REG2, 64 - PAGE_SHIFT, REG2; \
+	sllx		REG1, 11, REG1; \
+	andn		REG2, 0x7, REG2; \
+	add		REG1, REG2, REG1;
+
+/* Lookup a OBP mapping on VADDR in the prom_trans[] table at TL>0.
+ * If no entry is found, FAIL_LABEL will be branched to.  On success
+ * the resulting PTE value will be left in REG1.  VADDR is preserved
+ * by this routine.
+ */
+#define OBP_TRANS_LOOKUP(VADDR, REG1, REG2, REG3, FAIL_LABEL) \
+	sethi		%hi(prom_trans), REG1; \
+	or		REG1, %lo(prom_trans), REG1; \
+97:	ldx		[REG1 + 0x00], REG2; \
+	brz,pn		REG2, FAIL_LABEL; \
+	 nop; \
+	ldx		[REG1 + 0x08], REG3; \
+	add		REG2, REG3, REG3; \
+	cmp		REG2, VADDR; \
+	bgu,pt		%xcc, 98f; \
+	 cmp		VADDR, REG3; \
+	bgeu,pt		%xcc, 98f; \
+	 ldx		[REG1 + 0x10], REG3; \
+	sub		VADDR, REG2, REG2; \
+	ba,pt		%xcc, 99f; \
+	 add		REG3, REG2, REG1; \
+98:	ba,pt		%xcc, 97b; \
+	 add		REG1, (3 * 8), REG1; \
+99:
+
+	/* Do a kernel TSB lookup at tl>0 on VADDR+TAG, branch to OK_LABEL
+	 * on TSB hit.  REG1, REG2, REG3, and REG4 are used as temporaries
+	 * and the found TTE will be left in REG1.  REG3 and REG4 must
+	 * be an even/odd pair of registers.
+	 *
+	 * VADDR and TAG will be preserved and not clobbered by this macro.
+	 */
+	/* XXX non-8K base page size support... */
+#define KERN_TSB_LOOKUP_TL1(VADDR, TAG, REG1, REG2, REG3, REG4, OK_LABEL) \
+	sethi		%hi(swapper_tsb), REG1; \
+	or		REG1, %lo(swapper_tsb), REG1; \
+	srlx		VADDR, 13, REG2; \
+	and		REG2, (512 - 1), REG2; \
+	sllx		REG2, 4, REG2; \
+	add		REG1, REG2, REG2; \
+	ldda		[REG2] ASI_NUCLEUS_QUAD_LDD, REG3; \
+	cmp		REG3, TAG; \
+	be,a,pt		%xcc, OK_LABEL; \
+	 mov		REG4, REG1;
+
+#endif /* !(_SPARC64_TSB_H) */