[PATCH 40/62] x86/sev-es: Filter exceptions not supported from user-space

[Joerg Roedel]

From: Joerg Roedel <jroedel@xxxxxxx>

Currently only CPUID caused #VC exceptions are supported from
user-space. Filter the others out early.

Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
---
 arch/x86/kernel/sev-es.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index d128a9397639..84b5b8f7897a 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -209,6 +209,26 @@ static enum es_result handle_vc_exception(struct es_em_ctxt *ctxt,
 	return result;
 }
 
+static enum es_result context_filter(struct pt_regs *regs, long exit_code)
+{
+	enum es_result r = ES_OK;
+
+	if (user_mode(regs)) {
+		switch (exit_code) {
+		/* List of #VC exit-codes we support in user-space */
+		case SVM_EXIT_EXCP_BASE ... SVM_EXIT_LAST_EXCP:
+		case SVM_EXIT_CPUID:
+			r = ES_OK;
+			break;
+		default:
+			r = ES_UNSUPPORTED;
+			break;
+		}
+	}
+
+	return r;
+}
+
 static void forward_exception(struct es_em_ctxt *ctxt)
 {
 	long error_code = ctxt->fi.error_code;
@@ -245,6 +265,10 @@ dotraplinkage void do_vmm_communication(struct pt_regs *regs, unsigned long exit
 	ghcb_invalidate(ghcb);
 	result = init_em_ctxt(&ctxt, regs, exit_code);
 
+	/* Check if the exception is supported in the context we came from. */
+	if (result == ES_OK)
+		result = context_filter(regs, exit_code);
+
 	if (result == ES_OK)
 		result = handle_vc_exception(&ctxt, ghcb, exit_code);
 
-- 
2.17.1