[tip: x86/seves] x86/sev-es: Handle #DB Events

[tip-bot2 for Joerg Roedel]

The following commit has been merged into the x86/seves branch of tip:

Commit-ID:     cb1ad3ecea959593400dfac4f027dbc005e62c39
Gitweb:        https://git.kernel.org/tip/cb1ad3ecea959593400dfac4f027dbc005e62c39
Author:        Joerg Roedel <jroedel@xxxxxxx>
AuthorDate:    Mon, 07 Sep 2020 15:16:02 +02:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Wed, 09 Sep 2020 11:33:20 +02:00

x86/sev-es: Handle #DB Events

Handle #VC exceptions caused by #DB exceptions in the guest. Those
must be handled outside of instrumentation_begin()/end() so that the
handler will not be raised recursively.

Handle them by calling the kernel's debug exception handler.

Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lkml.kernel.org/r/20200907131613.12703-62-joro@xxxxxxxxxx
---
 arch/x86/kernel/sev-es.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 8867c48..79d5190 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -922,6 +922,14 @@ static enum es_result vc_handle_trap_ac(struct ghcb *ghcb,
 	return ES_EXCEPTION;
 }
 
+static __always_inline void vc_handle_trap_db(struct pt_regs *regs)
+{
+	if (user_mode(regs))
+		noist_exc_debug(regs);
+	else
+		exc_debug(regs);
+}
+
 static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,
 					 struct ghcb *ghcb,
 					 unsigned long exit_code)
@@ -1033,6 +1041,15 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
 	struct ghcb *ghcb;
 
 	lockdep_assert_irqs_disabled();
+
+	/*
+	 * Handle #DB before calling into !noinstr code to avoid recursive #DB.
+	 */
+	if (error_code == SVM_EXIT_EXCP_BASE + X86_TRAP_DB) {
+		vc_handle_trap_db(regs);
+		return;
+	}
+
 	instrumentation_begin();
 
 	/*