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

["tip-bot2 for Tony Luck" <tip-bot2@xxxxxxxxxxxxx>]

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@xxxxxxxxx>
AuthorDate:    Tue, 26 Oct 2021 15:00:44 -07:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Tested-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Link: https://lkml.kernel.org/r/20211026220050.697075-2-tony.luck@xxxxxxxxx
---
 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;