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Re: [Qemu-devel] [PATCH V2 2/4] pci: reserve 64 bit MMIO range for PCI h


From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] [PATCH V2 2/4] pci: reserve 64 bit MMIO range for PCI hotplug
Date: Wed, 18 May 2016 17:33:59 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0

On 05/18/2016 05:31 PM, Igor Mammedov wrote:
On Wed, 18 May 2016 17:12:09 +0300
Marcel Apfelbaum <address@hidden> wrote:

On 05/18/2016 05:11 PM, Michael S. Tsirkin wrote:
On Wed, May 18, 2016 at 03:59:29PM +0200, Igor Mammedov wrote:
On Sun, 15 May 2016 22:23:32 +0300
Marcel Apfelbaum <address@hidden> wrote:

Using the firmware assigned MMIO ranges for 64-bit PCI window
leads to zero space for hot-plugging PCI devices over 4G.

PC machines can use the whole CPU addressable range after
the space reserved for memory-hotplug.

Signed-off-by: Marcel Apfelbaum <address@hidden>
that patch also has side effect of unconditionally adding
QWordMemory() resource in PCI0._CRS
on all machine types with QEMU generated ACPI tables.

Have you tested that it won't break boot of legacy OSes
(XP, WS2003, old linux with 32bit kernel)?

It's almost sure it break it.
Maybe you can check _REV in _CRS to work around this for XP.

I'll try it.
but only after you check if just presence of QWord would crash XP,
so in case it doesn't crash we would keep _CRS simple static
structure.

I very vaguely recall that XP ignored QWord in PCI0._CRS,
but it was long time ago so it won't hurt to recheck.

Thanks for the pointer!
Marcel



Thanks,
Marcel


---
   hw/pci/pci.c | 16 ++++++++++++++--
   1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index bb605ef..44dd949 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -41,6 +41,7 @@
   #include "hw/hotplug.h"
   #include "hw/boards.h"
   #include "qemu/cutils.h"
+#include "hw/i386/pc.h"

   //#define DEBUG_PCI
   #ifdef DEBUG_PCI
@@ -2467,8 +2468,19 @@ static void pci_dev_get_w64(PCIBus *b, PCIDevice *dev, 
void *opaque)

   void pci_bus_get_w64_range(PCIBus *bus, Range *range)
   {
-    range->begin = range->end = 0;
-    pci_for_each_device_under_bus(bus, pci_dev_get_w64, range);
+    Object *machine = qdev_get_machine();
+    if (object_dynamic_cast(machine, TYPE_PC_MACHINE)) {
+        PCMachineState *pcms = PC_MACHINE(machine);
+        range->begin = pc_machine_get_reserved_memory_end(pcms);
+        if (!range->begin) {
+            range->begin = ROUND_UP(0x100000000ULL + pcms->above_4g_mem_size,
+                                    1ULL << 30);
+        }
+        range->end = 1ULL << 40; /* 40 bits physical */
+    } else {
+        range->begin = range->end = 0;
+        pci_for_each_device_under_bus(bus, pci_dev_get_w64, range);
+    }
   }

   static bool pcie_has_upstream_port(PCIDevice *dev)






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