[Qemu-devel] [PATCH 3/4] hw/pci: allow the caller of pci_bar_address() to ignore command register

[Laszlo Ersek]

The pci_bar_address() function calculates the start address of a given PCI
BAR. Its main purpose is supporting MemoryRegion mapping / unmapping in
pci_update_mappings(), which is guest-observable.

For that reason it contains heavy logic to enforce the validity of the
BAR, and this logic includes checks for the PCI command register:
- If the PCI_COMMAND_IO bit is clear in the command register, then all IO
  space BARs will be reported unmapped (all bits one),
- If the PCI_COMMAND_MEMORY bit is clear in the command register, then all
  MMIO space BARs will be reported unmapped (all bits one).

For an upcoming use case, we'd like pci_bar_address() to calculate the BAR
address from the config space *regardless* of the command register. Add a
new parameter that allows the caller to cut out the command register
verification.

All current callers preserve their behaviors.

Cc: Marcel Apfelbaum <mar...@redhat.com>
Cc: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Laszlo Ersek <ler...@redhat.com>
---
 include/hw/pci/pci.h |  2 ++
 hw/pci/pci.c         | 18 +++++++++++-------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index d44bc84..16b467b 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -314,6 +314,8 @@ void pci_register_vga(PCIDevice *pci_dev, MemoryRegion *mem,
                       MemoryRegion *io_lo, MemoryRegion *io_hi);
 void pci_unregister_vga(PCIDevice *pci_dev);
 pcibus_t pci_get_bar_addr(PCIDevice *pci_dev, int region_num);
+pcibus_t pci_bar_address(PCIDevice *d, int reg, uint8_t type, pcibus_t size,
+                         bool respect_command);
 
 int pci_add_capability(PCIDevice *pdev, uint8_t cap_id,
                        uint8_t offset, uint8_t size);
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 750f3da..61a70de 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1054,15 +1054,19 @@ pcibus_t pci_get_bar_addr(PCIDevice *pci_dev, int 
region_num)
     return pci_dev->io_regions[region_num].addr;
 }
 
-static pcibus_t pci_bar_address(PCIDevice *d,
-                               int reg, uint8_t type, pcibus_t size)
+pcibus_t pci_bar_address(PCIDevice *d, int reg, uint8_t type, pcibus_t size,
+                         bool respect_command)
 {
     pcibus_t new_addr, last_addr;
     int bar = pci_bar(d, reg);
-    uint16_t cmd = pci_get_word(d->config + PCI_COMMAND);
+    uint16_t cmd;
+
+    if (respect_command) {
+        cmd = pci_get_word(d->config + PCI_COMMAND);
+    }
 
     if (type & PCI_BASE_ADDRESS_SPACE_IO) {
-        if (!(cmd & PCI_COMMAND_IO)) {
+        if (respect_command && !(cmd & PCI_COMMAND_IO)) {
             return PCI_BAR_UNMAPPED;
         }
         new_addr = pci_get_long(d->config + bar) & ~(size - 1);
@@ -1076,7 +1080,7 @@ static pcibus_t pci_bar_address(PCIDevice *d,
         return new_addr;
     }
 
-    if (!(cmd & PCI_COMMAND_MEMORY)) {
+    if (respect_command && !(cmd & PCI_COMMAND_MEMORY)) {
         return PCI_BAR_UNMAPPED;
     }
     if (type & PCI_BASE_ADDRESS_MEM_TYPE_64) {
@@ -1134,7 +1138,7 @@ static void pci_update_mappings(PCIDevice *d)
         if (!r->size)
             continue;
 
-        new_addr = pci_bar_address(d, i, r->type, r->size);
+        new_addr = pci_bar_address(d, i, r->type, r->size, true);
 
         /* This bar isn't changed */
         if (new_addr == r->addr)
@@ -2427,7 +2431,7 @@ static void pci_dev_get_w64(PCIBus *b, PCIDevice *dev, 
void *opaque)
             !(r->type & PCI_BASE_ADDRESS_MEM_TYPE_64)) {
             continue;
         }
-        region_range.begin = pci_bar_address(dev, i, r->type, r->size);
+        region_range.begin = pci_bar_address(dev, i, r->type, r->size, true);
         region_range.end = region_range.begin + r->size;
 
         if (region_range.begin == PCI_BAR_UNMAPPED) {
-- 
1.8.3.1