[PATCH 5/9] vpci/header: Implement guest BAR register handlers

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

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@xxxxxxxx>
---
 xen/drivers/vpci/header.c  | 69 +++++++++++++++++++++++++++++++++++++-
 xen/include/xen/pci_regs.h |  1 +
 xen/include/xen/vpci.h     |  3 ++
 3 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
index 5218b1af247e..793f79ece831 100644
--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -400,12 +400,72 @@ 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;
+    bar->guest_addr &= ~(0xffffffffull << (hi ? 32 : 0));
+    bar->guest_addr |= (uint64_t)val << (hi ? 32 : 0);
 }
 
 static uint32_t guest_bar_read(const struct pci_dev *pdev, unsigned int reg,
                                void *data)
 {
-    return 0xffffffff;
+    struct vpci_bar *bar = data;
+    uint32_t val;
+    bool hi = false;
+
+    switch ( bar->type )
+    {
+    case VPCI_BAR_MEM64_HI:
+        ASSERT(reg > PCI_BASE_ADDRESS_0);
+        bar--;
+        hi = true;
+        /* fallthrough */
+    case VPCI_BAR_MEM64_LO:
+    {
+        if ( hi )
+            val = bar->guest_addr >> 32;
+        else
+            val = bar->guest_addr & 0xffffffff;
+        if ( (val & PCI_BASE_ADDRESS_MEM_MASK_32) ==  
PCI_BASE_ADDRESS_MEM_MASK_32 )
+        {
+            /* Guests detects BAR's properties and sizes. */
+            if ( hi )
+                val = bar->size >> 32;
+            else
+                val = 0xffffffff & ~(bar->size - 1);
+        }
+        if ( !hi )
+        {
+            val |= 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);
+        break;
+    }
+    case VPCI_BAR_MEM32:
+    {
+        val = bar->guest_addr;
+        if ( (val & PCI_BASE_ADDRESS_MEM_MASK_32) ==  
PCI_BASE_ADDRESS_MEM_MASK_32 )
+            val = 0xffffffff & ~(bar->size - 1);
+        val |= PCI_BASE_ADDRESS_MEM_TYPE_32;
+        val |= bar->prefetchable ? PCI_BASE_ADDRESS_MEM_PREFETCH : 0;
+        break;
+    }
+    default:
+        val = bar->guest_addr;
+        break;
+    }
+    return val;
 }
 
 static void rom_write(const struct pci_dev *pdev, unsigned int reg,
@@ -522,6 +582,13 @@ static int add_bar_handlers(struct pci_dev *pdev, bool 
is_hwdom)
             if ( rc )
                 return rc;
         }
+        /*
+         * It is neither safe nor secure to initialize guest's view of the BARs
+         * with real values which are used by the hardware domain, so assign
+         * all zeros to guest's view of the BARs, so the guest can perform
+         * proper PCI device enumeration and assign BARs on its own.
+         */
+        bars[i].guest_addr = 0;
     }
     return 0;
 }
diff --git a/xen/include/xen/pci_regs.h b/xen/include/xen/pci_regs.h
index cc4ee3b83e5c..038eb18c5357 100644
--- a/xen/include/xen/pci_regs.h
+++ b/xen/include/xen/pci_regs.h
@@ -103,6 +103,7 @@
 #define  PCI_BASE_ADDRESS_MEM_TYPE_64  0x04    /* 64 bit address */
 #define  PCI_BASE_ADDRESS_MEM_PREFETCH 0x08    /* prefetchable? */
 #define  PCI_BASE_ADDRESS_MEM_MASK     (~0x0fUL)
+#define  PCI_BASE_ADDRESS_MEM_MASK_32  (~0x0fU)
 #define  PCI_BASE_ADDRESS_IO_MASK      (~0x03UL)
 /* bit 1 is reserved if address_space = 1 */
 
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index 4aa2941a1081..db86b8e7fa3c 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -77,7 +77,10 @@ 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