[xen master] hvmloader/PCI: skip huge BARs in certain calculations

[patchbot@xxxxxxx]

commit 57acad12a09ffa490e870ebe17596aad858f0191
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Mar 6 10:19:29 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Mar 6 10:19:29 2024 +0100

    hvmloader/PCI: skip huge BARs in certain calculations
    
    BARs of size 2Gb and up can't possibly fit below 4Gb: Both the bottom of
    the lower 2Gb range and the top of the higher 2Gb range have special
    purpose. Don't even have them influence whether to (perhaps) relocate
    low RAM.
    
    Reported-by: Neowutran <xen@xxxxxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 tools/firmware/hvmloader/pci.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/tools/firmware/hvmloader/pci.c b/tools/firmware/hvmloader/pci.c
index 257a6feb61..c3c61ca060 100644
--- a/tools/firmware/hvmloader/pci.c
+++ b/tools/firmware/hvmloader/pci.c
@@ -33,6 +33,13 @@ uint32_t pci_mem_start = HVM_BELOW_4G_MMIO_START;
 const uint32_t pci_mem_end = RESERVED_MEMBASE;
 uint64_t pci_hi_mem_start = 0, pci_hi_mem_end = 0;
 
+/*
+ * BARs larger than this value are put in 64-bit space unconditionally.  That
+ * is, such BARs also don't play into the determination of how big the lowmem
+ * MMIO hole needs to be.
+ */
+#define BAR_RELOC_THRESH GB(1)
+
 enum virtual_vga virtual_vga = VGA_none;
 unsigned long igd_opregion_pgbase = 0;
 
@@ -286,9 +293,11 @@ void pci_setup(void)
             bars[i].bar_reg = bar_reg;
             bars[i].bar_sz  = bar_sz;
 
-            if ( ((bar_data & PCI_BASE_ADDRESS_SPACE) ==
-                  PCI_BASE_ADDRESS_SPACE_MEMORY) ||
-                 (bar_reg == PCI_ROM_ADDRESS) )
+            if ( is_64bar && bar_sz > BAR_RELOC_THRESH )
+                bar64_relocate = 1;
+            else if ( ((bar_data & PCI_BASE_ADDRESS_SPACE) ==
+                       PCI_BASE_ADDRESS_SPACE_MEMORY) ||
+                      (bar_reg == PCI_ROM_ADDRESS) )
                 mmio_total += bar_sz;
 
             nr_bars++;
@@ -367,7 +376,7 @@ void pci_setup(void)
             pci_mem_start = hvm_info->low_mem_pgend << PAGE_SHIFT;
     }
 
-    if ( mmio_total > (pci_mem_end - pci_mem_start) )
+    if ( mmio_total > (pci_mem_end - pci_mem_start) || bar64_relocate )
     {
         printf("Low MMIO hole not large enough for all devices,"
                " relocating some BARs to 64-bit\n");
@@ -430,7 +439,8 @@ void pci_setup(void)
 
         /*
          * Relocate to high memory if the total amount of MMIO needed
-         * is more than the low MMIO available.  Because devices are
+         * is more than the low MMIO available or BARs bigger than
+         * BAR_RELOC_THRESH are present.  Because devices are
          * processed in order of bar_sz, this will preferentially
          * relocate larger devices to high memory first.
          *
@@ -446,8 +456,9 @@ void pci_setup(void)
          *   the code here assumes it to be.)
          * Should either of those two conditions change, this code will break.
          */
-        using_64bar = bars[i].is_64bar && bar64_relocate
-            && (mmio_total > (mem_resource.max - mem_resource.base));
+        using_64bar = bars[i].is_64bar && bar64_relocate &&
+            (mmio_total > (mem_resource.max - mem_resource.base) ||
+             bar_sz > BAR_RELOC_THRESH);
         bar_data = pci_readl(devfn, bar_reg);
 
         if ( (bar_data & PCI_BASE_ADDRESS_SPACE) ==
@@ -467,7 +478,8 @@ void pci_setup(void)
                 resource = &mem_resource;
                 bar_data &= ~PCI_BASE_ADDRESS_MEM_MASK;
             }
-            mmio_total -= bar_sz;
+            if ( bar_sz <= BAR_RELOC_THRESH )
+                mmio_total -= bar_sz;
         }
         else
         {
--
generated by git-patchbot for /home/xen/git/xen.git#master