linux-kernel - [PATCH v11 1/7] x86/sgx: Add new sgx_epc

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Message-Id: <20211026220050.697075-2-tony.luck@intel.com>
Date:   Tue, 26 Oct 2021 15:00:44 -0700
From:   Tony Luck <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>, x86@...nel.org
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        naoya.horiguchi@....com, Andrew Morton <akpm@...ux-foundation.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Cathy Zhang <cathy.zhang@...el.com>, linux-sgx@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>
Subject: [PATCH v11 1/7] 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.

Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
Tested-by: Reinette Chatre <reinette.chatre@...el.com>
Signed-off-by: Tony Luck <tony.luck@...el.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 63d3de02bbcc..825aa91516c8 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 4628acec0009..5906471156c5 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;
-- 
2.31.1