[PATCH] x86/sgx: Add poison handling to reclaimer

From: Reinette Chatre
Date: Tue Jan 18 2022 - 18:05:16 EST


The machine check recovery handling in SGX added the changes
listed below to the freeing of pages in sgx_free_epc_page().
The SGX reclaimer contains an open coded version of
sgx_free_epc_page() and thus did not obtain the changes in
support of poison handling.

The changes made to EPC page freeing in support of poison handling
are:
1) A new SGX_EPC_PAGE_IS_FREE flag is set when the EPC page is
freed. Introduced in commit d6d261bded8a ("x86/sgx: Add new
sgx_epc_page flag bit to mark free pages").
2) A new "poison" field in struct sgx_epc_page is used to
determine whether a newly freed EPC page should be placed
on the list of poisoned or list of free pages. Introduced
in commit 992801ae9243 ("x86/sgx: Initial poison handling
for dirty and free pages").
3) The owner field in struct sgx_epc_page is cleared when the EPC
page is freed. Introduced in commit 992801ae9243 ("x86/sgx:
Initial poison handling for dirty and free pages").

Replace the open coded enclave page freeing code in the reclaimer
with sgx_free_epc_page() to obtain support for poison page handling.

Fixes: d6d261bded8a ("x86/sgx: Add new sgx_epc_page flag bit to mark free pages")
Fixes: 992801ae9243 ("x86/sgx: Initial poison handling for dirty and free pages")
Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
---
arch/x86/kernel/cpu/sgx/main.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 4b41efc9e367..997a5d0bc488 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -418,13 +418,7 @@ static void sgx_reclaim_pages(void)
kref_put(&encl_page->encl->refcount, sgx_encl_release);
epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;

- section = &sgx_epc_sections[epc_page->section];
- node = section->node;
-
- spin_lock(&node->lock);
- list_add_tail(&epc_page->list, &node->free_page_list);
- spin_unlock(&node->lock);
- atomic_long_inc(&sgx_nr_free_pages);
+ sgx_free_epc_page(epc_page);
}
}

--
2.25.1