[PATCH 3/4] x86/sgx: Fine grained SGX MCA behavior for virtualization

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

When VM guest access a SGX EPC page with memory failure, current
behavior will kill the guest, expected only kill the SGX application
inside it.

To fix it we send SIGBUS with code BUS_MCEERR_AR and some extra
information for hypervisor to inject #MC information to guest, which is
helpful in SGX case.

Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>
---
 arch/x86/kernel/cpu/sgx/main.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 8e4bc6453d26..81801ab0009e 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -710,6 +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;
+	int ret = 0;
 
 	/*
 	 * mm/memory-failure.c calls this routine for all errors
@@ -726,8 +728,22 @@ int arch_memory_failure(unsigned long pfn, int flags)
 	 * error. The signal may help the task understand why the
 	 * enclave is broken.
 	 */
-	if (flags & MF_ACTION_REQUIRED)
-		force_sig(SIGBUS);
+	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,
+					PAGE_SHIFT);
+			if (ret < 0)
+				pr_err("Memory failure: Error sending signal to %s:%d: %d\n",
+					current->comm, current->pid, ret);
+		} else
+			force_sig(SIGBUS);
+	}
 
 	section = &sgx_epc_sections[page->section];
 	node = section->node;
-- 
2.25.1