[PATCH] x86/sgx: Do not update sgx_nr_free_pages in sgx_setup_epc_section()

[PATCH] x86/sgx: Do not update sgx_nr_free_pages in sgx_setup_epc_section()

[Jarkko Sakkinen]

NUMA patches introduced this change to __sgx_sanitize_pages():

-		if (!ret)
-			list_move(&page->list, &section->page_list);
-		else
+		if (!ret) {
+			/*
+			 * page is now sanitized.  Make it available via the SGX
+			 * page allocator:
+			 */
+			list_del(&page->list);
+			sgx_free_epc_page(page);
+		} else {
+			/* The page is not yet clean - move to the dirty list. */
 			list_move_tail(&page->list, &dirty);
-
-		spin_unlock(&section->lock);
+		}

This was done for the reason that it is best to keep the logic to assign
available-for-use EPC pages to the correct NUMA lists in a single location.

The problem is that the sgx_nr_free_pages is also incremented by
sgx_free_epc_pages(), and thus it ends up having double the number of pages
available.

The count was even before NUMA patches kind of out-of-sync, i.e. free pages
count was incremented before putting them to the free list, but it didn't
matter that much, because sanitization is fairly fast and it only prevented
ksgxd to trigger small time after the system had powered on.

Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v2:
* Wrote more verbose and detailed description what is going on.
* Split out from the patches. This is urgent - the attributes can wait.
 arch/x86/kernel/cpu/sgx/main.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 13a7599ce7d4..7df7048cb1c9 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -657,7 +657,6 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
 		list_add_tail(&section->pages[i].list, &sgx_dirty_page_list);
 	}
 
-	sgx_nr_free_pages += nr_pages;
 	return true;
 }
 
-- 
2.31.1

[tip: x86/sgx] x86/sgx: Do not update sgx_nr_free_pages in sgx_setup_epc_section()

[tip-bot2 for Jarkko Sakkinen]

The following commit has been merged into the x86/sgx branch of tip:

Commit-ID:     ae40aaf6bdbf0354a75b8284a0de453fcf5f4d32
Gitweb:        https://git.kernel.org/tip/ae40aaf6bdbf0354a75b8284a0de453fcf5f4d32
Author:        Jarkko Sakkinen <jarkko@kernel.org>
AuthorDate:    Thu, 08 Apr 2021 12:29:24 +03:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Thu, 08 Apr 2021 17:24:42 +02:00

x86/sgx: Do not update sgx_nr_free_pages in sgx_setup_epc_section()

The commit in Fixes: changed the SGX EPC page sanitization to end up in
sgx_free_epc_page() which puts clean and sanitized pages on the free
list.

This was done for the reason that it is best to keep the logic to assign
available-for-use EPC pages to the correct NUMA lists in a single
location.

sgx_nr_free_pages is also incremented by sgx_free_epc_pages() but those
pages which are being added there per EPC section do not belong to the
free list yet because they haven't been sanitized yet - they land on the
dirty list first and the sanitization happens later when ksgxd starts
massaging them.

So remove that addition there and have sgx_free_epc_page() do that
solely.

 [ bp: Sanitize commit message too. ]

Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210408092924.7032-1-jarkko@kernel.org
---
 arch/x86/kernel/cpu/sgx/main.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 92cb11d..ad90474 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -656,7 +656,6 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
 		list_add_tail(&section->pages[i].list, &sgx_dirty_page_list);
 	}
 
-	sgx_nr_free_pages += nr_pages;
 	return true;
 }