[PATCH 4/4] cc-swiotlb: Allow set swiotlb watermark from cmdline

GuoRui.Yu
2023-01-28T08:33:36Z

Signed-off-by: GuoRui.Yu <GuoRui.Yu@linux.alibaba.com>
---
.../admin-guide/kernel-parameters.txt | 11 ++++++
kernel/dma/cc-swiotlb.c | 34 ++++++++++++++++++-
2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6cfa6e3996cf..ad510e392998 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/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]
diff --git a/kernel/dma/cc-swiotlb.c b/kernel/dma/cc-swiotlb.c
index e85d3ce2272f..ff1cc52189b9 100644
--- a/kernel/dma/cc-swiotlb.c
+++ b/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);

--
2.31.1