[Xen-devel] [PATCH] ioemu: passthough: add no_wb option for pci conf write

[Qing He <qing.he@xxxxxxxxx>]

Current pt_pci_write_config always writes back to real pci conf
space. However, in the case of MSI address and data registers,
if guest changes the affinity of the interrupt, stale data will
be written to these registers. This is particularly a problem
if Xen uses per-CPU vector, where the interrupt in question fails
to work. This patch fixes this by adding an option to disable the
write back of certain controls.

Signed-off-by: Qing He <qing.he@xxxxxxxxx>
---

diff --git a/hw/pass-through.c b/hw/pass-through.c
index 8d80755..b1a3b09 100644
--- a/hw/pass-through.c
+++ b/hw/pass-through.c
@@ -626,6 +626,7 @@ static struct pt_reg_info_tbl pt_emu_reg_msi_tbl[] = {
         .init_val   = 0x00000000,
         .ro_mask    = 0x00000003,
         .emu_mask   = 0xFFFFFFFF,
+        .no_wb      = 1,
         .init       = pt_common_reg_init,
         .u.dw.read  = pt_long_reg_read,
         .u.dw.write = pt_msgaddr32_reg_write,
@@ -638,6 +639,7 @@ static struct pt_reg_info_tbl pt_emu_reg_msi_tbl[] = {
         .init_val   = 0x00000000,
         .ro_mask    = 0x00000000,
         .emu_mask   = 0xFFFFFFFF,
+        .no_wb      = 1,
         .init       = pt_msgaddr64_reg_init,
         .u.dw.read  = pt_long_reg_read,
         .u.dw.write = pt_msgaddr64_reg_write,
@@ -650,6 +652,7 @@ static struct pt_reg_info_tbl pt_emu_reg_msi_tbl[] = {
         .init_val   = 0x0000,
         .ro_mask    = 0x0000,
         .emu_mask   = 0xFFFF,
+        .no_wb      = 1,
         .init       = pt_msgdata_reg_init,
         .u.w.read   = pt_word_reg_read,
         .u.w.write  = pt_msgdata_reg_write,
@@ -662,6 +665,7 @@ static struct pt_reg_info_tbl pt_emu_reg_msi_tbl[] = {
         .init_val   = 0x0000,
         .ro_mask    = 0x0000,
         .emu_mask   = 0xFFFF,
+        .no_wb      = 1,
         .init       = pt_msgdata_reg_init,
         .u.w.read   = pt_word_reg_read,
         .u.w.write  = pt_msgdata_reg_write,
@@ -1550,10 +1554,12 @@ static void pt_pci_write_config(PCIDevice *d, uint32_t 
address, uint32_t val,
     val >>= ((address & 3) << 3);
 
 out:
-    ret = pci_write_block(pci_dev, address, (uint8_t *)&val, len);
+    if (!reg->no_wb) {
+        ret = pci_write_block(pci_dev, address, (uint8_t *)&val, len);
 
-    if (!ret)
-        PT_LOG("Error: pci_write_block failed. return value[%d].\n", ret);
+        if (!ret)
+            PT_LOG("Error: pci_write_block failed. return value[%d].\n", ret);
+    }
 
     if (pm_state != NULL && pm_state->flags & PT_FLAG_TRANSITING)
         /* set QEMUTimer */
diff --git a/hw/pass-through.h b/hw/pass-through.h
index 028a03e..3c79885 100644
--- a/hw/pass-through.h
+++ b/hw/pass-through.h
@@ -364,6 +364,8 @@ struct pt_reg_info_tbl {
     uint32_t ro_mask;
     /* reg emulate field mask (ON:emu, OFF:passthrough) */
     uint32_t emu_mask;
+    /* no write back allowed */
+    uint32_t no_wb;
     /* emul reg initialize method */
     conf_reg_init init;
     union {

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