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Date: Tue, 9 Jan 2024 13:48:24 +0800
From: Jun Miao <jun.miao@...el.com>
To: kirill.shutemov@...ux.intel.com,
dave.hansen@...ux.intel.com
Cc: jun.miao@...el.com,
x86@...nel.org,
linux-coco@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: [PATCH] x86/tdx: Optimize try_accept_memory() to reduce 1GB page accepted failed times
Since the current TDX module ABI spec TDG.MEM.PAGE.ACCEPT Leaf show:
"Level of the Secure EPT leaf entry that maps the private page to be
accepted: either 0 (4KB) or 1 (2MB)".
There is not 1G page accept dynamically, if every time try to accept 1G
size but always fail, then cost more time from two cases:
- When size < 1G, judge failed return 0
- Really TDCALL<ACCEPT_PAGE> 1G failed when size >= 1G
So skip the 1G and optimize it to 2M directly to save time.
Run the eatmemory with different memories to get the cost time as follow:
[root@...guest ~]# ./eatmemory 8G
Currently total memory: 100169027584
Currently avail memory: 99901911040
Eating 8589934592 bytes in chunks of 1024...
Start time：1704699207487 ms
End time：1704699222966 ms
Cost time: 15479 ms
#
# Compare with/without this optimization
#
# Hardware: ArcherCity Sapphire Rapids 128cores
# Test eatmemory: https://github.com/jmiao2018/eatmemory.git
# Detail test log link: https://github.com/jmiao2018/eatmemory/blob/master/log-tdx.txt
#
# Accept Memeory Sizes Before(ms) After(ms) Trigger 1G Failed Times Reduce Time%
# .................... .......... ......... ....................... .............
#
1G 3414 3402 751824 -12(-0.035%)
2G 3853 3804 1015126 -349(-0.128%)
4G 7773 7561 1557834 -212(-0.281%)
8G 15479 15173 2633686 -306(-0.201%)
16G 31527 30379 4785649 -1148(-0.378%)
32G 65058 63723 9087686 -1335(-0.209%)
64G 133379 128354 17693366 -5025(-0.391%)
Co-developed-by: Zhiquan Li <zhiquan1.li@...el.com>
Signed-off-by: Jun Miao <jun.miao@...el.com>
---
arch/x86/coco/tdx/tdx-shared.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
index 1655aa56a0a5..1694b7eba93b 100644
--- a/arch/x86/coco/tdx/tdx-shared.c
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -18,7 +18,7 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
* Pass the page physical address to the TDX module to accept the
* pending, private page.
*
- * Bits 2:0 of RCX encode page size: 0 - 4K, 1 - 2M, 2 - 1G.
+ * Bits 2:0 of RCX encode page size: 0 - 4K, 1 - 2M.
*/
switch (pg_level) {
case PG_LEVEL_4K:
@@ -27,9 +27,6 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
case PG_LEVEL_2M:
page_size = TDX_PS_2M;
break;
- case PG_LEVEL_1G:
- page_size = TDX_PS_1G;
- break;
default:
return 0;
}
@@ -55,11 +52,14 @@ bool tdx_accept_memory(phys_addr_t start, phys_addr_t end)
* Try larger accepts first. It gives chance to VMM to keep
* 1G/2M Secure EPT entries where possible and speeds up
* process by cutting number of hypercalls (if successful).
- */
+ * Since per current TDX spec, only support for adding 4KB or
+ * 2MB page dynamically.
+ * /
- accept_size = try_accept_one(start, len, PG_LEVEL_1G);
- if (!accept_size)
+ if (IS_ALIGNED(start, PMD_SIZE) && len >= PMD_SIZE)
accept_size = try_accept_one(start, len, PG_LEVEL_2M);
+
+ /* The 4KB page case or accept 2MB page failed case. */
if (!accept_size)
accept_size = try_accept_one(start, len, PG_LEVEL_4K);
if (!accept_size)
--
2.32.0
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