hvmloader/pci: try to avoid placing BARs in RMRRs

Try to avoid placing PCI BARs over RMRRs:

- If mmio_hole_size is not specified, and the existing MMIO range has
  RMRRs in it, and there is space to expand the hole in lowmem without
  moving more memory, then make the MMIO hole as large as possible.

- When placing RMRRs, find the next RMRR higher than the current base
  in the lowmem mmio hole.  If it overlaps, skip ahead of it and find
  the next one.

This certainly won't work in all cases, but it should work in a
significant number of cases.  Additionally, users should be able to
work around problems by setting mmio_hole_size larger in the guest
config.

Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

--- a/tools/firmware/hvmloader/pci.c
+++ b/tools/firmware/hvmloader/pci.c
@@ -38,6 +38,45 @@ uint64_t pci_hi_mem_start = 0, pci_hi_mem_end = 0;
 enum virtual_vga virtual_vga = VGA_none;
 unsigned long igd_opregion_pgbase = 0;
 
+/* Check if the specified range conflicts with any reserved device memory. */
+static bool check_overlap_all(uint64_t start, uint64_t size)
+{
+    unsigned int i;
+
+    for ( i = 0; i < memory_map.nr_map; i++ )
+    {
+        if ( memory_map.map[i].type == E820_RESERVED &&
+             check_overlap(start, size,
+                           memory_map.map[i].addr,
+                           memory_map.map[i].size) )
+            return true;
+    }
+
+    return false;
+}
+
+/* Find the lowest RMRR ending above base but below 4G. */
+static int find_next_rmrr(uint32_t base)
+{
+    unsigned int i;
+    int next_rmrr = -1;
+    uint64_t end, min_end = 1ULL << 32;
+
+    for ( i = 0; i < memory_map.nr_map ; i++ )
+    {
+        end = memory_map.map[i].addr + memory_map.map[i].size;
+
+        if ( memory_map.map[i].type == E820_RESERVED &&
+             end > base && end <= min_end )
+        {
+            next_rmrr = i;
+            min_end = end;
+        }
+    }
+
+    return next_rmrr;
+}
+
 void pci_setup(void)
 {
     uint8_t is_64bar, using_64bar, bar64_relocate = 0;
@@ -46,6 +85,7 @@ void pci_setup(void)
     uint32_t vga_devfn = 256;
     uint16_t class, vendor_id, device_id;
     unsigned int bar, pin, link, isa_irq;
+    int next_rmrr;
 
     /* Resources assignable to PCI devices via BARs. */
     struct resource {
@@ -299,6 +339,15 @@ void pci_setup(void)
                     || (((pci_mem_start << 1) >> PAGE_SHIFT)
                         >= hvm_info->low_mem_pgend)) )
             pci_mem_start <<= 1;
+
+        /*
+         * Try to accommodate RMRRs in our MMIO region on a best-effort basis.
+         * If we have RMRRs in the range, then make pci_mem_start just after
+         * hvm_info->low_mem_pgend.
+         */
+        if ( pci_mem_start > (hvm_info->low_mem_pgend << PAGE_SHIFT) &&
+             check_overlap_all(pci_mem_start, pci_mem_end-pci_mem_start) )
+            pci_mem_start = hvm_info->low_mem_pgend << PAGE_SHIFT;
     }
 
     if ( mmio_total > (pci_mem_end - pci_mem_start) )
@@ -352,6 +401,8 @@ void pci_setup(void)
     io_resource.base = 0xc000;
     io_resource.max = 0x10000;
 
+    next_rmrr = find_next_rmrr(pci_mem_start);
+
     /* Assign iomem and ioport resources in descending order of size. */
     for ( i = 0; i < nr_bars; i++ )
     {
@@ -407,6 +459,18 @@ void pci_setup(void)
         }
 
         base = (resource->base  + bar_sz - 1) & ~(uint64_t)(bar_sz - 1);
+
+        /* If we're using mem_resource, check for RMRR conflicts. */
+        while ( resource == &mem_resource &&
+                next_rmrr >= 0 &&
+                check_overlap(base, bar_sz,
+                              memory_map.map[next_rmrr].addr,
+                              memory_map.map[next_rmrr].size) )
+        {
+            base = memory_map.map[next_rmrr].addr + memory_map.map[next_rmrr].size;
+            base = (base + bar_sz - 1) & ~(bar_sz - 1);
+            next_rmrr = find_next_rmrr(base);
+        }
+
         bar_data |= (uint32_t)base;
         bar_data_upper = (uint32_t)(base >> 32);
         base += bar_sz;