[PATCH v2 05/11] vpci/header: Implement guest BAR register handlers

[Oleksandr Andrushchenko <andr2000@gmail.com>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

Emulate guest BAR register values: this allows creating a guest view
of the registers and emulates size and properties probe as it is done
during PCI device enumeration by the guest.

ROM BAR is only handled for the hardware domain and for guest domains
there is a stub: at the moment PCI expansion ROM is x86 only, so it
might not be used by other architectures without emulating x86. Other
use-cases may include using that expansion ROM before Xen boots, hence
no emulation is needed in Xen itself. Or when a guest wants to use the
ROM code which seems to be rare.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

---
Since v1:
 - re-work guest read/write to be much simpler and do more work on write
   than read which is expected to be called more frequently
 - removed one too obvious comment

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 xen/drivers/vpci/header.c | 30 +++++++++++++++++++++++++++++-
 xen/include/xen/vpci.h    |  3 +++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
index 1ce98795fcca..ec4d215f36ff 100644
--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -400,12 +400,38 @@ static void bar_write(const struct pci_dev *pdev, unsigned int reg,
 static void guest_bar_write(const struct pci_dev *pdev, unsigned int reg,
                             uint32_t val, void *data)
 {
+    struct vpci_bar *bar = data;
+    bool hi = false;
+
+    if ( bar->type == VPCI_BAR_MEM64_HI )
+    {
+        ASSERT(reg > PCI_BASE_ADDRESS_0);
+        bar--;
+        hi = true;
+    }
+    else
+    {
+        val &= PCI_BASE_ADDRESS_MEM_MASK;
+        val |= bar->type == VPCI_BAR_MEM32 ? PCI_BASE_ADDRESS_MEM_TYPE_32
+                                           : PCI_BASE_ADDRESS_MEM_TYPE_64;
+        val |= bar->prefetchable ? PCI_BASE_ADDRESS_MEM_PREFETCH : 0;
+    }
+
+    bar->guest_addr &= ~(0xffffffffull << (hi ? 32 : 0));
+    bar->guest_addr |= (uint64_t)val << (hi ? 32 : 0);
+
+    bar->guest_addr &= ~(bar->size - 1) | ~PCI_BASE_ADDRESS_MEM_MASK;
 }
 
 static uint32_t guest_bar_read(const struct pci_dev *pdev, unsigned int reg,
                                void *data)
 {
-    return 0xffffffff;
+    const struct vpci_bar *bar = data;
+
+    if ( bar->type == VPCI_BAR_MEM64_HI )
+        return bar->guest_addr >> 32;
+
+    return bar->guest_addr;
 }
 
 static void rom_write(const struct pci_dev *pdev, unsigned int reg,
@@ -522,6 +548,8 @@ static int add_bar_handlers(const struct pci_dev *pdev, bool is_hwdom)
             if ( rc )
                 return rc;
         }
+
+        bars[i].guest_addr = 0;
     }
     return 0;
 }
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index 912cbc6aa7ad..9eaf99f356fe 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -81,7 +81,10 @@ struct vpci {
     struct vpci_header {
         /* Information about the PCI BARs of this device. */
         struct vpci_bar {
+            /* Physical view of the BAR. */
             uint64_t addr;
+            /* Guest view of the BAR. */
+            uint64_t guest_addr;
             uint64_t size;
             enum {
                 VPCI_BAR_EMPTY,
-- 
2.25.1