hardenedbsd/HardenedBSD
1
0
Fork 0
mirror of https://git.hardenedbsd.org/hardenedbsd/HardenedBSD.git synced 2024-11-14 06:12:01 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity

x86/xen: use UNUSABLE e820 regions for external mappings

Browse Source 
Using holes in the memory map to create external mappings (for example grants
or foreign maps) can be dangerous, as the guest might not have enough knowledge
of whether such holes are maybe MMIO of some devices.

Workaround this by using UNUSABLE e820 ranges as scratch space for external
mappings.  The e820 memory map provided to dom0 is based on the native one, but
since PVH dom0 uses second stage translation, the UNUSABLE ranges on the host
memory map doesn't affect it, and we can also guarantee no device MMIO uses
those.

Additionally, any RAM in the e820 not available to dom0 because dom0
memory has been limited on the command line, or because those are in use by
Xen, are converted to UNUSABLE in the dom0 memory map.

Note that domU don't usually have UNUSABLE ranges in their memory maps, and
hence the logic introduced here won't help in avoiding conflicts with MMIO
regions.  However the usage of external mappings on domUs is in general
limited, and the logic introduced here simply won't be helpful to them, but
won't regress the current state.

Sponsored by: Cloud Software Group
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D46123
This commit is contained in:
Roger Pau Monné 2024-02-15 11:42:17 +01:00
parent baa006f342
commit 69c47485b5
1 changed files with 50 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
sys/x86/xen/hvm.c
View File

@ -47,6 +47,7 @@
#include <machine/cpu.h>
#include <machine/md_var.h>
#include <machine/metadata.h>
#include <machine/pc/bios.h>
#include <machine/smp.h>
#include <x86/apicreg.h>
@ -548,3 +549,52 @@ xen_has_iommu_maps(void)
return (regs[0] & XEN_HVM_CPUID_IOMMU_MAPPINGS);
}
int
xen_arch_init_physmem(device_t dev, struct rman *mem)
{
static struct bios_smap smap[128];
struct xen_memory_map memmap = {
.nr_entries = nitems(smap),
};
unsigned int i;
int error;
set_xen_guest_handle(memmap.buffer, smap);
error = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
if (error != 0)
return (error);
/*
* Fill with UNUSABLE regions, as it's always fine to use those for
* foreign mappings, they will never be populated.
*/
for (i = 0; i < memmap.nr_entries; i++) {
const vm_paddr_t max_phys = cpu_getmaxphyaddr();
vm_paddr_t start, end;
if (smap[i].type != SMAP_TYPE_ACPI_ERROR)
continue;
start = round_page(smap[i].base);
/* In 32bit mode we possibly need to truncate the addresses. */
end = MIN(trunc_page(smap[i].base + smap[i].length) - 1,
max_phys);
if (start >= end)
continue;
if (bootverbose != 0)
device_printf(dev,
"scratch mapping region @ [%016jx, %016jx]\n",
start, end);
error = rman_manage_region(mem, start, end);
if (error != 0)
device_printf(dev,
"unable to add scratch region [%016jx, %016jx]: %d\n",
start, end, error);
}
return (0);
}