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Re: [PATCH] rumpkernel dependencies

From: Samuel Thibault
Subject: Re: [PATCH] rumpkernel dependencies
Date: Sun, 29 Mar 2020 01:19:47 +0100
User-agent: NeoMutt/20170609 (1.8.3)

--- a/src/common_interface.c
+++ b/src/common_interface.c
@@ -290,11 +290,13 @@ pci_device_map_range(struct pci_device *dev, pciaddr_t 

     /* Make sure that there isn't already a mapping with the same base and
      * size.
+     * If there is, use it.
     for (i = 0; i < devp->num_mappings; i++) {
         if ((devp->mappings[i].base == base)
             && (devp->mappings[i].size == size)) {
-            return EINVAL;
+            *addr = devp->mappings[i].memory;
+            return 0;

I don't think we can just return it. Think of a process that uses
libpciaccess in several components, which happen to use the same
mapping. One will call pci_device_map_range(), the other will call
pci_device_map_range(), at some point the first will call
pci_device_unmap_memory_range() and then oops the second has unexpected
lost access to the mapping.

I don't really know why libpciaccess maintainers thought it should
exclude mapping the same base&size. Maybe you need to confront the rump
usage case with upstream libpciaccess, so they perhaps just drop that
check entirely, and thus allow *several* mappings of the region?


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