Lay the groundwork for processing #VC exceptions in the handler.
This includes clearing the GHCB, decoding the insn that triggered
this #VC, and continuing execution after the exception has been
processed.
Based on Linux 6d7d0603ca7c397a07efc88e314e38b4242a3a8d.
Signed-off-by: Varad Gautam <varad.gautam@xxxxxxxx>
Signed-off-by: Vasant Karasulli <vkarasulli@xxxxxxx>
---
lib/x86/amd_sev_vc.c | 87 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 87 insertions(+)
diff --git a/lib/x86/amd_sev_vc.c b/lib/x86/amd_sev_vc.c
index f622703..1eefaf0 100644
--- a/lib/x86/amd_sev_vc.c
+++ b/lib/x86/amd_sev_vc.c
@@ -1,15 +1,102 @@
// SPDX-License-Identifier: GPL-2.0
+/*
+ * AMD SEV-ES #VC exception handling.
+ * Adapted from Linux@6d7d0603ca:
+ * - arch/x86/kernel/sev.c
+ * - arch/x86/kernel/sev-shared.c
+ */
#include "amd_sev.h"
+#include "svm.h"
extern phys_addr_t ghcb_addr;
+static void vc_ghcb_invalidate(struct ghcb *ghcb)
+{
+ ghcb->save.sw_exit_code = 0;
+ memset(ghcb->save.valid_bitmap, 0, sizeof(ghcb->save.valid_bitmap));
+}
+
+static bool vc_decoding_needed(unsigned long exit_code)
+{
+ /* Exceptions don't require to decode the instruction */
+ return !(exit_code >= SVM_EXIT_EXCP_BASE &&
+ exit_code <= SVM_EXIT_LAST_EXCP);
+}
+
+static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
+{
+ unsigned char buffer[MAX_INSN_SIZE];
+ int ret;
+
+ memcpy(buffer, (unsigned char *)ctxt->regs->rip, MAX_INSN_SIZE);
+
+ ret = insn_decode(&ctxt->insn, buffer, MAX_INSN_SIZE, INSN_MODE_64);
+ if (ret < 0)
+ return ES_DECODE_FAILED;
+ else
+ return ES_OK;
+}
+
+static enum es_result vc_init_em_ctxt(struct es_em_ctxt *ctxt,
+ struct ex_regs *regs,
+ unsigned long exit_code)
+{
+ enum es_result ret = ES_OK;
+
+ memset(ctxt, 0, sizeof(*ctxt));
+ ctxt->regs = regs;
+
+ if (vc_decoding_needed(exit_code))
+ ret = vc_decode_insn(ctxt);
+
+ return ret;
+}
+
+static void vc_finish_insn(struct es_em_ctxt *ctxt)
+{
+ ctxt->regs->rip += ctxt->insn.length;
+}
+
+static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,
+ struct ghcb *ghcb,
+ unsigned long exit_code)
+{
+ enum es_result result;
+
+ switch (exit_code) {
+ default:
+ /*
+ * Unexpected #VC exception
+ */
+ result = ES_UNSUPPORTED;
+ }
+
+ return result;
+}
+
void handle_sev_es_vc(struct ex_regs *regs)
{
struct ghcb *ghcb = (struct ghcb *) ghcb_addr;
+ unsigned long exit_code = regs->error_code;
+ struct es_em_ctxt ctxt;
+ enum es_result result;
if (!ghcb) {
/* TODO: kill guest */
return;
}
+
+ vc_ghcb_invalidate(ghcb);
+ result = vc_init_em_ctxt(&ctxt, regs, exit_code);
+ if (result == ES_OK)
+ result = vc_handle_exitcode(&ctxt, ghcb, exit_code);
+ if (result == ES_OK) {
+ vc_finish_insn(&ctxt);
+ } else {
+ printf("Unable to handle #VC exitcode, exit_code=%lx result=%x\n",
+ exit_code, result);
+ }
+
+ return;
}
--
2.34.1
