powerpc/pseries: Read TLB Block Invalidate Characteristics

The PAPR document specifies the TLB Block Invalidate Characteristics
which tells for each pair of segment base page size, actual page size,
the size of the block the hcall H_BLOCK_REMOVE supports.

These characteristics are loaded at boot time in a new table
hblkr_size. The table is separate from the mmu_psize_def because this
is specific to the pseries platform.

A new init function, pseries_lpar_read_hblkrm_characteristics() is
added to read the characteristics. It is called from
pSeries_setup_arch().

Fixes: ba2dd8a2 ("powerpc/pseries/mm: call H_BLOCK_REMOVE")
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190920130523.20441-2-ldufour@linux.ibm.com

arch/powerpc/platforms/pseries/lpar.c

@@ -56,6 +56,15 @@ EXPORT_SYMBOL(plpar_hcall);
 EXPORT_SYMBOL(plpar_hcall9);
 EXPORT_SYMBOL(plpar_hcall_norets);
 
+/*
+ * H_BLOCK_REMOVE supported block size for this page size in segment who's base
+ * page size is that page size.
+ *
+ * The first index is the segment base page size, the second one is the actual
+ * page size.
+ */
+static int hblkrm_size[MMU_PAGE_COUNT][MMU_PAGE_COUNT] __ro_after_init;
+
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
 static u8 dtl_mask = DTL_LOG_PREEMPT;
 #else
@@ -1311,6 +1320,137 @@ static void do_block_remove(unsigned long number, struct ppc64_tlb_batch *batch,
 		(void)call_block_remove(pix, param, true);
 }
 
+/*
+ * TLB Block Invalidate Characteristics
+ *
+ * These characteristics define the size of the block the hcall H_BLOCK_REMOVE
+ * is able to process for each couple segment base page size, actual page size.
+ *
+ * The ibm,get-system-parameter properties is returning a buffer with the
+ * following layout:
+ *
+ * [ 2 bytes size of the RTAS buffer (excluding these 2 bytes) ]
+ * -----------------
+ * TLB Block Invalidate Specifiers:
+ * [ 1 byte LOG base 2 of the TLB invalidate block size being specified ]
+ * [ 1 byte Number of page sizes (N) that are supported for the specified
+ *          TLB invalidate block size ]
+ * [ 1 byte Encoded segment base page size and actual page size
+ *          MSB=0 means 4k segment base page size and actual page size
+ *          MSB=1 the penc value in mmu_psize_def ]
+ * ...
+ * -----------------
+ * Next TLB Block Invalidate Specifiers...
+ * -----------------
+ * [ 0 ]
+ */
+static inline void set_hblkrm_bloc_size(int bpsize, int psize,
+					unsigned int block_size)
+{
+	if (block_size > hblkrm_size[bpsize][psize])
+		hblkrm_size[bpsize][psize] = block_size;
+}
+
+/*
+ * Decode the Encoded segment base page size and actual page size.
+ * PAPR specifies:
+ *   - bit 7 is the L bit
+ *   - bits 0-5 are the penc value
+ * If the L bit is 0, this means 4K segment base page size and actual page size
+ * otherwise the penc value should be read.
+ */
+#define HBLKRM_L_MASK		0x80
+#define HBLKRM_PENC_MASK	0x3f
+static inline void __init check_lp_set_hblkrm(unsigned int lp,
+					      unsigned int block_size)
+{
+	unsigned int bpsize, psize;
+
+	/* First, check the L bit, if not set, this means 4K */
+	if ((lp & HBLKRM_L_MASK) == 0) {
+		set_hblkrm_bloc_size(MMU_PAGE_4K, MMU_PAGE_4K, block_size);
+		return;
+	}
+
+	lp &= HBLKRM_PENC_MASK;
+	for (bpsize = 0; bpsize < MMU_PAGE_COUNT; bpsize++) {
+		struct mmu_psize_def *def = &mmu_psize_defs[bpsize];
+
+		for (psize = 0; psize < MMU_PAGE_COUNT; psize++) {
+			if (def->penc[psize] == lp) {
+				set_hblkrm_bloc_size(bpsize, psize, block_size);
+				return;
+			}
+		}
+	}
+}
+
+#define SPLPAR_TLB_BIC_TOKEN		50
+
+/*
+ * The size of the TLB Block Invalidate Characteristics is variable. But at the
+ * maximum it will be the number of possible page sizes *2 + 10 bytes.
+ * Currently MMU_PAGE_COUNT is 16, which means 42 bytes. Use a cache line size
+ * (128 bytes) for the buffer to get plenty of space.
+ */
+#define SPLPAR_TLB_BIC_MAXLENGTH	128
+
+void __init pseries_lpar_read_hblkrm_characteristics(void)
+{
+	unsigned char local_buffer[SPLPAR_TLB_BIC_MAXLENGTH];
+	int call_status, len, idx, bpsize;
+
+	spin_lock(&rtas_data_buf_lock);
+	memset(rtas_data_buf, 0, RTAS_DATA_BUF_SIZE);
+	call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
+				NULL,
+				SPLPAR_TLB_BIC_TOKEN,
+				__pa(rtas_data_buf),
+				RTAS_DATA_BUF_SIZE);
+	memcpy(local_buffer, rtas_data_buf, SPLPAR_TLB_BIC_MAXLENGTH);
+	local_buffer[SPLPAR_TLB_BIC_MAXLENGTH - 1] = '\0';
+	spin_unlock(&rtas_data_buf_lock);
+
+	if (call_status != 0) {
+		pr_warn("%s %s Error calling get-system-parameter (0x%x)\n",
+			__FILE__, __func__, call_status);
+		return;
+	}
+
+	/*
+	 * The first two (2) bytes of the data in the buffer are the length of
+	 * the returned data, not counting these first two (2) bytes.
+	 */
+	len = be16_to_cpu(*((u16 *)local_buffer)) + 2;
+	if (len > SPLPAR_TLB_BIC_MAXLENGTH) {
+		pr_warn("%s too large returned buffer %d", __func__, len);
+		return;
+	}
+
+	idx = 2;
+	while (idx < len) {
+		u8 block_shift = local_buffer[idx++];
+		u32 block_size;
+		unsigned int npsize;
+
+		if (!block_shift)
+			break;
+
+		block_size = 1 << block_shift;
+
+		for (npsize = local_buffer[idx++];
+		     npsize > 0 && idx < len; npsize--)
+			check_lp_set_hblkrm((unsigned int) local_buffer[idx++],
+					    block_size);
+	}
+
+	for (bpsize = 0; bpsize < MMU_PAGE_COUNT; bpsize++)
+		for (idx = 0; idx < MMU_PAGE_COUNT; idx++)
+			if (hblkrm_size[bpsize][idx])
+				pr_info("H_BLOCK_REMOVE supports base psize:%d psize:%d block size:%d",
+					bpsize, idx, hblkrm_size[bpsize][idx]);
+}
+
 /*
  * Take a spinlock around flushes to avoid bouncing the hypervisor tlbie
  * lock.

arch/powerpc/platforms/pseries/pseries.h

@@ -112,5 +112,6 @@ static inline unsigned long cmo_get_page_size(void)
 int dlpar_workqueue_init(void);
 
 void pseries_setup_rfi_flush(void);
+void pseries_lpar_read_hblkrm_characteristics(void);
 
 #endif /* _PSERIES_PSERIES_H */

arch/powerpc/platforms/pseries/setup.c

@@ -744,6 +744,7 @@ static void __init pSeries_setup_arch(void)
 
 	pseries_setup_rfi_flush();
 	setup_stf_barrier();
+	pseries_lpar_read_hblkrm_characteristics();
 
 	/* By default, only probe PCI (can be overridden by rtas_pci) */
 	pci_add_flags(PCI_PROBE_ONLY);