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Subject[PATCH v3 1/7] x86/sgx: Provide indication of life-cycle of EPC pages
Date
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.

It would be good to use the sgx_epc_page->owner field as an indicator
of where an EPC page is currently in that cycle (owner != NULL means
the EPC page is IN-USE). But there is one caller, sgx_alloc_va_page(),
that calls with NULL.

Make the following changes:

1) Change the type of "owner" to "void *" (it can have other types
besides "struct sgx_encl_page *).
2) Add a check to sgx_free_epc_page(). If the caller specified the
owner as NULL, then set the owner field to self-reference the
SGX epc page itself.
3) Reset owner to NULL in sgx_free_epc_page().

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/cpu/sgx/main.c | 3 ++-
arch/x86/kernel/cpu/sgx/sgx.h | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 63d3de02bbcc..17d09186a6c2 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -581,7 +581,7 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
for ( ; ; ) {
page = __sgx_alloc_epc_page();
if (!IS_ERR(page)) {
- page->owner = owner;
+ page->owner = owner ? owner : page;
break;
}

@@ -624,6 +624,7 @@ void sgx_free_epc_page(struct sgx_epc_page *page)

spin_lock(&node->lock);

+ page->owner = NULL;
list_add_tail(&page->list, &node->free_page_list);
sgx_nr_free_pages++;

diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index 4628acec0009..4e1a410b8a62 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -29,7 +29,7 @@
struct sgx_epc_page {
unsigned int section;
unsigned int flags;
- struct sgx_encl_page *owner;
+ void *owner;
struct list_head list;
};

--
2.29.2
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