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Subject[tip: x86/sgx] x86/sgx: Add new sgx_epc_page flag bit to mark free pages
The following commit has been merged into the x86/sgx branch of tip:

Commit-ID: d6d261bded8a57aed4faa12d08a5b193418d3aa4
Gitweb: https://git.kernel.org/tip/d6d261bded8a57aed4faa12d08a5b193418d3aa4
Author: Tony Luck <tony.luck@intel.com>
AuthorDate: Tue, 26 Oct 2021 15:00:44 -07:00
Committer: Dave Hansen <dave.hansen@linux.intel.com>
CommitterDate: Mon, 15 Nov 2021 11:13:16 -08:00

x86/sgx: Add new sgx_epc_page flag bit to mark free pages

SGX EPC pages go through the following life cycle:

DIRTY ---> FREE ---> IN-USE --\
^ |
\-----------------/

Recovery action for poison for a DIRTY or FREE page is simple. Just
make sure never to allocate the page. IN-USE pages need some extra
handling.

Add a new flag bit SGX_EPC_PAGE_IS_FREE that is set when a page
is added to a free list and cleared when the page is allocated.

Notes:

1) These transitions are made while holding the node->lock so that
future code that checks the flags while holding the node->lock
can be sure that if the SGX_EPC_PAGE_IS_FREE bit is set, then the
page is on the free list.

2) Initially while the pages are on the dirty list the
SGX_EPC_PAGE_IS_FREE bit is cleared.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lkml.kernel.org/r/20211026220050.697075-2-tony.luck@intel.com
---
arch/x86/kernel/cpu/sgx/main.c | 2 ++
arch/x86/kernel/cpu/sgx/sgx.h | 3 +++
2 files changed, 5 insertions(+)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 63d3de0..825aa91 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -472,6 +472,7 @@ static struct sgx_epc_page *__sgx_alloc_epc_page_from_node(int nid)
page = list_first_entry(&node->free_page_list, struct sgx_epc_page, list);
list_del_init(&page->list);
sgx_nr_free_pages--;
+ page->flags = 0;

spin_unlock(&node->lock);

@@ -626,6 +627,7 @@ void sgx_free_epc_page(struct sgx_epc_page *page)

list_add_tail(&page->list, &node->free_page_list);
sgx_nr_free_pages++;
+ page->flags = SGX_EPC_PAGE_IS_FREE;

spin_unlock(&node->lock);
}
diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index 4628ace..5906471 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -26,6 +26,9 @@
/* Pages, which are being tracked by the page reclaimer. */
#define SGX_EPC_PAGE_RECLAIMER_TRACKED BIT(0)

+/* Pages on free list */
+#define SGX_EPC_PAGE_IS_FREE BIT(1)
+
struct sgx_epc_page {
unsigned int section;
unsigned int flags;
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