[PATCH 4/4] x86/sgx: Fine grained SGX MCA behavior for normal case

[Zhiquan Li <zhiquan1.li@intel.com>]

When the application accesses a SGX EPC page with memory failure, the
task will receive a SIGBUS signal without any extra info, unless the EPC
page has SGX_EPC_PAGE_IS_VEPC flag. However, in some cases, we only use
SGX in sub-task and we don’t expect the entire task group be killed due
to a SGX EPC page for a sub-task has memory failure.

To fix it, we extend the solution for normal case. That is, the SGX
regular EPC page with memory failure will trigger a SIGBUS signal with
code BUS_MCEERR_AR and additional info, so that the user has opportunity
to make further decision.

Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>
---
 arch/x86/kernel/cpu/sgx/main.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 81801ab0009e..b43fb374b5cd 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -710,7 +710,8 @@ int arch_memory_failure(unsigned long pfn, int flags)
 	struct sgx_epc_page *page = sgx_paddr_to_page(pfn << PAGE_SHIFT);
 	struct sgx_epc_section *section;
 	struct sgx_numa_node *node;
-	struct sgx_vepc_page *owner;
+	struct sgx_encl_page *owner;
+	unsigned long vaddr;
 	int ret = 0;
 
 	/*
@@ -729,14 +730,17 @@ int arch_memory_failure(unsigned long pfn, int flags)
 	 * enclave is broken.
 	 */
 	if (flags & MF_ACTION_REQUIRED) {
-		/*
-		 * In case the error memory is accessed by VM guest, provide
-		 * extra info for hypervisor to make further decision but not
-		 * simply kill it.
-		 */
-		if (page->flags & SGX_EPC_PAGE_IS_VEPC) {
-			owner = (struct sgx_vepc_page *)page->owner;
-			ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)owner->vaddr,
+		owner = page->owner;
+		if (owner) {
+			/*
+			 * Provide extra info to the task so that it can make further
+			 * decision but not simply kill it.
+			 */
+			if (page->flags & SGX_EPC_PAGE_IS_VEPC)
+				vaddr = ((struct sgx_vepc_page *)owner)->vaddr;
+			else
+				vaddr = owner->desc & PAGE_MASK;
+			ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)vaddr,
 					PAGE_SHIFT);
 			if (ret < 0)
 				pr_err("Memory failure: Error sending signal to %s:%d: %d\n",
-- 
2.25.1