dm: pci: fix the MMIO regions overlap when getting bar size

PCI spec says that the procedure of sizing a BAR is as follows:
1) disable the decode via command register
2) save the original value of BAR register
3) write all-1 to the BAR register
4) read BAR register back, calculate the size
5) restore the original value to BAR register
6) re-enable the decode via command register

Some driver does not disable the decode of BAR register via the
command register before sizing a BAR. This will lead to a overlay
of the BAR addresses when trying to register the intermediate
BAR address via register_bar. A stateful variable sizing is used
to keep track of such kind of BAR address changes and workaroud
this violation.

Currently this issue is only found when audio device is passed
through to Windows 10 guest. When it is fixed in the Windows
audio driver, this patch should be reverted.

v1 -> v2:
- change the commit message to add the procedure of BAR sizing from
  PCI spec

Tracked-On: #2962
Signed-off-by: Jian Jun Chen <jian.jun.chen@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@intel.com>
Acked-by: Yu Wang <yu1.wang@intel.com>

Author: chejianj

devicemodel/hw/pci/core.c

@@ -595,15 +595,17 @@ memen(struct pci_vdev *dev)
  */
 static void
 update_bar_address(struct vmctx *ctx, struct pci_vdev *dev, uint64_t addr,
-	int idx, int type)
+	int idx, int type, bool ignore_reg_unreg)
 {
-	bool decode;
+	bool decode = false;
 	uint64_t orig_addr = dev->bar[idx].addr;
 
-	if (dev->bar[idx].type == PCIBAR_IO)
-		decode = porten(dev);
-	else
-		decode = memen(dev);
+	if (!ignore_reg_unreg) {
+		if (dev->bar[idx].type == PCIBAR_IO)
+			decode = porten(dev);
+		else
+			decode = memen(dev);
+	}
 
 	if (decode)
 		unregister_bar(dev, idx);
@@ -629,7 +631,7 @@ update_bar_address(struct vmctx *ctx, struct pci_vdev *dev, uint64_t addr,
 		register_bar(dev, idx);
 
 	/* update bar mapping */
-	if (dev->dev_ops->vdev_update_bar_map)
+	if (dev->dev_ops->vdev_update_bar_map && decode)
 		dev->dev_ops->vdev_update_bar_map(ctx, dev, idx, orig_addr);
 }
 
@@ -2048,6 +2050,7 @@ pci_cfgrw(struct vmctx *ctx, int vcpu, int in, int bus, int slot, int func,
 	struct pci_vdev_ops *ops;
 	int idx, needcfg;
 	uint64_t addr, bar, mask;
+	bool decode, ignore_reg_unreg = false;
 
 	bi = pci_businfo[bus];
 	if (bi != NULL) {
@@ -2130,6 +2133,30 @@ pci_cfgrw(struct vmctx *ctx, int vcpu, int in, int bus, int slot, int func,
 				return;
 			idx = (coff - PCIR_BAR(0)) / 4;
 			mask = ~(dev->bar[idx].size - 1);
+
+			if (dev->bar[idx].type == PCIBAR_IO)
+				decode = porten(dev);
+			else
+				decode = memen(dev);
+
+			/* Some driver does not disable the decode of BAR
+			 * register via the command register before sizing a
+			 * BAR. This will lead to a overlay of the BAR
+			 * addresses when trying to register the intermediate
+			 * BAR address via register_bar. A stateful variable
+			 * sizing is used to keep track of such kind of BAR
+			 * address changes and workaroud this violation.
+			 */
+			if (decode) {
+				if (!dev->bar[idx].sizing && (*eax == ~0U)) {
+					dev->bar[idx].sizing = true;
+					ignore_reg_unreg = true;
+				} else if (dev->bar[idx].sizing && (*eax != ~0U)) {
+					dev->bar[idx].sizing = false;
+					ignore_reg_unreg = true;
+				}
+			}
+
 			switch (dev->bar[idx].type) {
 			case PCIBAR_NONE:
 				dev->bar[idx].addr = bar = 0;
@@ -2143,15 +2170,17 @@ pci_cfgrw(struct vmctx *ctx, int vcpu, int in, int bus, int slot, int func,
 				 */
 				if (addr != dev->bar[idx].addr) {
 					update_bar_address(ctx, dev, addr, idx,
-							   PCIBAR_IO);
+							   PCIBAR_IO,
+							   ignore_reg_unreg);
 				}
 				break;
 			case PCIBAR_MEM32:
 				addr = bar = *eax & mask;
 				bar |= PCIM_BAR_MEM_SPACE | PCIM_BAR_MEM_32;
 				if (addr != dev->bar[idx].addr) {
 					update_bar_address(ctx, dev, addr, idx,
-							   PCIBAR_MEM32);
+							   PCIBAR_MEM32,
+							   ignore_reg_unreg);
 				}
 				break;
 			case PCIBAR_MEM64:
@@ -2160,7 +2189,8 @@ pci_cfgrw(struct vmctx *ctx, int vcpu, int in, int bus, int slot, int func,
 				       PCIM_BAR_MEM_PREFETCH;
 				if (addr != (uint32_t)dev->bar[idx].addr) {
 					update_bar_address(ctx, dev, addr, idx,
-							   PCIBAR_MEM64);
+							   PCIBAR_MEM64,
+							   ignore_reg_unreg);
 				}
 				break;
 			case PCIBAR_MEMHI64:
@@ -2170,7 +2200,8 @@ pci_cfgrw(struct vmctx *ctx, int vcpu, int in, int bus, int slot, int func,
 				bar = addr >> 32;
 				if (bar != dev->bar[idx - 1].addr >> 32) {
 					update_bar_address(ctx, dev, addr, idx - 1,
-							   PCIBAR_MEMHI64);
+							   PCIBAR_MEMHI64,
+							   ignore_reg_unreg);
 				}
 				break;
 			default:

devicemodel/include/pci_core.h

@@ -32,6 +32,7 @@
 #include <sys/queue.h>
 
 #include <assert.h>
+#include <stdbool.h>
 #include "types.h"
 #include "pcireg.h"
 
@@ -104,6 +105,7 @@ struct pcibar {
 	enum pcibar_type	type;		/* io or memory */
 	uint64_t		size;
 	uint64_t		addr;
+	bool			sizing;
 };
 
 #define PI_NAMESZ	40