cc-swiotlb: Allow set swiotlb watermark from cmdline

Signed-off-by: GuoRui.Yu <GuoRui.Yu@linux.alibaba.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -6090,6 +6090,17 @@
 			         wouldn't be automatically used by the kernel
 			noforce -- Never use bounce buffers (for debugging)
 
+	cc_swiotlb=	[X86]
+			Format: { [<int>, <int>, <int>, <int>]| force ]}
+			Set the swiotlb TLB buffer initial size for Confidential Computing like
+			TDX and SEV-SNP.
+			<int> -- Number of I/O TLB of 256 bytes
+			<int> -- Number of I/O TLB of 4 KiB
+			<int> -- Number of I/O TLB of 64 KiB
+			<int> -- Number of I/O TLB of 256 KiB
+			force -- force using of cc bounce buffers even if they
+			         wouldn't be automatically used by the kernel (for debugging)
+
 	switches=	[HW,M68k]
 
 	sysctl.*=	[KNL]

kernel/dma/cc-swiotlb.c

@@ -52,6 +52,32 @@ enum SLOT_SIZE {
 
 const unsigned int SLOT_SIZES[NR_OF_SIZES] = {512, 2048, 4096, 16 * 1024, 512 * 1024};
 unsigned int WATERMARK_SLOT_SIZE[NR_OF_SIZES] = {256, 16384, 8192, 1024, 32};
+static bool swiotlb_force_bounce = false;
+
+static int __init
+setup_io_tlb_watermark(char *str)
+{
+	int i;
+	size_t size;
+
+	for (i = 0; i < NR_OF_SIZES; i++) {
+		if (isdigit(*str)) {
+			size = simple_strtoul(str, &str, 0);
+			WATERMARK_SLOT_SIZE[i] = size;
+
+			if (*str == ',')
+				++str;
+		}
+		else
+			break;
+	}
+
+	if (!strcmp(str, "force"))
+		swiotlb_force_bounce = true;
+
+	return 0;
+}
+early_param("cc_swiotlb", setup_io_tlb_watermark);
 
 struct slot_terrace {
 	struct list_head slots_by_size[NR_OF_SIZES];
@@ -330,6 +356,7 @@ static void cc_populate_pages(void)
 	size_t i, j, k;
 	const size_t max_bytes_per_alloc = (MAX_ORDER_NR_PAGES << PAGE_SHIFT);
 	size_t remain_alloc_size, rounds, round_size, round_slot_nr;
+	size_t size = 0;
 
 	for (i = 0; i < NR_OF_SIZES; i++) {
 		if (atomic_read(&terrace.free_count_by_size[i]) > WATERMARK_SLOT_SIZE[i])
@@ -377,6 +404,11 @@ static void cc_populate_pages(void)
 			spin_unlock_irqrestore(&terrace.lock_by_size[i], flags);
 		}
 	}
+
+	for (i = 0; i < NR_OF_SIZES; i++) {
+		size += (size_t)atomic_read(&terrace.total_count_by_size[i]) * SLOT_SIZES[i];
+	}
+	pr_info("bounce buffer size adjusted to %luMB", size >> 20);
 }
 
 static int kccd(void *p)
@@ -437,7 +469,7 @@ void __init swiotlb_init(bool addressing_limit, unsigned int flags)
 		return;
 	}
 
-	io_tlb_default_mem.force_bounce = cc_platform_has(CC_ATTR_MEM_ENCRYPT);
+	io_tlb_default_mem.force_bounce = cc_platform_has(CC_ATTR_MEM_ENCRYPT) || swiotlb_force_bounce;
 
 	xa_init_flags(io_tlb_default_mem.mapping, 0);