xen/pt: allow QEMU to request MSI unmasking at bind time

When a MSI interrupt is bound to a guest using
xc_domain_update_msi_irq (XEN_DOMCTL_bind_pt_irq) the interrupt is
left masked by default.

This causes problems with guests that first configure interrupts and
clean the per-entry MSIX table mask bit and afterwards enable MSIX
globally. In such scenario the Xen internal msixtbl handlers would not
detect the unmasking of MSIX entries because vectors are not yet
registered since MSIX is not enabled, and vectors would be left
masked.

Introduce a new flag in the gflags field to signal Xen whether a MSI
interrupt should be unmasked after being bound.

This also requires to track the mask register for MSI interrupts, so
QEMU can also notify to Xen whether the MSI interrupt should be bound
masked or unmasked

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reported-by: Andreas Kinzler <hfp@posteo.de>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>

1 files changed, 18 insertions, 2 deletions

diff --git a/hw/xen/xen_pt_config_init.c b/hw/xen/xen_pt_config_init.c
index 1f04ec5eec..a3ce33e78b 100644
--- a/hw/xen/xen_pt_config_init.c
+++ b/hw/xen/xen_pt_config_init.c
@@ -1315,6 +1315,22 @@ static int xen_pt_msgdata_reg_write(XenPCIPassthroughState *s,
     return 0;
 }
 
+static int xen_pt_mask_reg_write(XenPCIPassthroughState *s, XenPTReg *cfg_entry,
+                                 uint32_t *val, uint32_t dev_value,
+                                 uint32_t valid_mask)
+{
+    int rc;
+
+    rc = xen_pt_long_reg_write(s, cfg_entry, val, dev_value, valid_mask);
+    if (rc) {
+        return rc;
+    }
+
+    s->msi->mask = *val;
+
+    return 0;
+}
+
 /* MSI Capability Structure reg static information table */
 static XenPTRegInfo xen_pt_emu_reg_msi[] = {
     /* Next Pointer reg */
@@ -1393,7 +1409,7 @@ static XenPTRegInfo xen_pt_emu_reg_msi[] = {
         .emu_mask   = 0xFFFFFFFF,
         .init       = xen_pt_mask_reg_init,
         .u.dw.read  = xen_pt_long_reg_read,
-        .u.dw.write = xen_pt_long_reg_write,
+        .u.dw.write = xen_pt_mask_reg_write,
     },
     /* Mask reg (if PCI_MSI_FLAGS_MASKBIT set, for 64-bit devices) */
     {
@@ -1404,7 +1420,7 @@ static XenPTRegInfo xen_pt_emu_reg_msi[] = {
         .emu_mask   = 0xFFFFFFFF,
         .init       = xen_pt_mask_reg_init,
         .u.dw.read  = xen_pt_long_reg_read,
-        .u.dw.write = xen_pt_long_reg_write,
+        .u.dw.write = xen_pt_mask_reg_write,
     },
     /* Pending reg (if PCI_MSI_FLAGS_MASKBIT set, for 32-bit devices) */
     {