0616-libxl-workaround-for-Windows-PV-drivers-removing-con.patch

From 13173fb5e3e683b97f6f8a7fdb1be7da1c4913ee Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
 <marmarek@invisiblethingslab.com>
Date: Thu, 27 Oct 2022 21:16:18 +0200
Subject: [PATCH] libxl: workaround for Windows PV drivers removing
 control/shutdown node
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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win-pv-drivers 8.x remove control/shutdown node as an acknowledgement,
instead of just clearing the content. This means the subsequent write
will create it anew, with default permissions (dom0 write, guest read).
Such permissions won't allow the guest to acknowledge subsequent
requests.

Workaround the issue by explicitly setting permissions after the write.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
 tools/libs/light/libxl_domain.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/tools/libs/light/libxl_domain.c b/tools/libs/light/libxl_domain.c
index 324a4c6607e7..25cde778352d 100644
--- a/tools/libs/light/libxl_domain.c
+++ b/tools/libs/light/libxl_domain.c
@@ -767,7 +767,12 @@ int libxl__domain_pvcontrol(libxl__egc *egc, libxl__xswait_state *pvcontrol,
                             domid_t domid, const char *cmd)
 {
     STATE_AO_GC(pvcontrol->ao);
+    libxl_ctx *ctx = libxl__gc_owner(gc);
     const char *shutdown_path;
+    xs_transaction_t t;
+    struct xs_permissions perms[] = {
+        { .id = domid, .perms = XS_PERM_NONE },
+    };
     int rc;
 
     rc = libxl__domain_pvcontrol_available(gc, domid);
@@ -781,9 +786,28 @@ int libxl__domain_pvcontrol(libxl__egc *egc, libxl__xswait_state *pvcontrol,
     if (!shutdown_path)
         return ERROR_FAIL;
 
-    rc = libxl__xs_printf(gc, XBT_NULL, shutdown_path, "%s", cmd);
-    if (rc)
+ retry_transaction:
+    t = xs_transaction_start(ctx->xsh);
+    if (!t)
+        return ERROR_FAIL;
+
+    rc = libxl__xs_printf(gc, t, shutdown_path, "%s", cmd);
+    if (rc) {
+        xs_transaction_end(ctx->xsh, t, 1);
         return rc;
+    }
+
+    if (!xs_set_permissions(ctx->xsh, t, shutdown_path, perms, ARRAY_SIZE(perms))) {
+        xs_transaction_end(ctx->xsh, t, 1);
+        return ERROR_FAIL;
+    }
+
+    if (!xs_transaction_end(ctx->xsh, t, 0)) {
+        if (errno == EAGAIN)
+            goto retry_transaction;
+        else
+            return ERROR_FAIL;
+    }
 
     pvcontrol->path = shutdown_path;
     pvcontrol->what = GCSPRINTF("guest acknowledgement of %s request", cmd);
-- 
2.44.0