[PATCH v3 63/75] x86/sev-es: Handle #DB Events

Joerg Roedel
2020-04-28T15:17:13Z

From: Joerg Roedel <jroedel@suse.de>

Handle #VC exceptions caused by #DB exceptions in the guest. Do not
forward them to the hypervisor and handle them with do_debug() instead.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/kernel/sev-es.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 050a15da9ae5..03095bc7b563 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -882,6 +882,19 @@ static enum es_result vc_handle_trap_ac(struct ghcb *ghcb,
return ES_EXCEPTION;
}

+static enum es_result vc_handle_trap_db(struct ghcb *ghcb,
+ struct es_em_ctxt *ctxt)
+{
+ /*
+ * Calling do_debug() directly does not work, because it might enable
+ * IRQs and the GHCB is active. Forward the exception and call it later
+ * from vc_forward_exception().
+ */
+ ctxt->fi.vector = X86_TRAP_DB;
+ ctxt->fi.error_code = 0;
+ return ES_EXCEPTION;
+}
+
static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,
struct ghcb *ghcb,
unsigned long exit_code)
@@ -895,6 +908,9 @@ static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,
case SVM_EXIT_WRITE_DR7:
result = vc_handle_dr7_write(ghcb, ctxt);
break;
+ case SVM_EXIT_EXCP_BASE + X86_TRAP_DB:
+ result = vc_handle_trap_db(ghcb, ctxt);
+ break;
case SVM_EXIT_EXCP_BASE + X86_TRAP_AC:
result = vc_handle_trap_ac(ghcb, ctxt);
break;
@@ -960,6 +976,9 @@ static void vc_forward_exception(struct es_em_ctxt *ctxt)
case X86_TRAP_AC:
do_alignment_check(ctxt->regs, error_code);
break;
+ case X86_TRAP_DB:
+ do_debug(ctxt->regs, error_code);
+ break;
default:
pr_emerg("Unsupported exception in #VC instruction emulation - can't continue\n");
BUG();
--
2.17.1