Since guest resource management work it's now possible to have a page
assigned to a domain without a valid M2P entry. Some pathes in the code
rely on the fact a GFN returned from mfn_to_gfn() for such a page
is not valid as well, i.e. see arch_iommu_populate_page_table().
For systems without 512GB contiguous RAM M2P entries were already
correctly initialized on boot with INVALID_M2P_ENTRY (~0UL) but
on systems where M2P could be covered by a single 1GB page directory
0x77 poison was used instead. That eventually resulted in a crash
during IOMMU construction on systems without shared PTs enabled.
While here fixup compat M2P entries as well.
Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
---
xen/arch/x86/x86_64/mm.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 1919cae..a741d4e 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -574,8 +574,9 @@ void __init paging_init(void)
page_to_mfn(l1_pg),
1UL << (2 * PAGETABLE_ORDER),
PAGE_HYPERVISOR);
+ /* Fill with INVALID_M2P_ENTRY. */
memset((void *)(RDWR_MPT_VIRT_START + (i << L2_PAGETABLE_SHIFT)),
- 0x77, 1UL << L3_PAGETABLE_SHIFT);
+ 0xFF, 1UL << L3_PAGETABLE_SHIFT);
ASSERT(!l2_table_offset(va));
/* NB. Cannot be GLOBAL: guest user mode should not see it. */
@@ -666,9 +667,10 @@ void __init paging_init(void)
page_to_mfn(l1_pg),
1UL << PAGETABLE_ORDER,
PAGE_HYPERVISOR);
+ /* Fill with INVALID_M2P_ENTRY. */
memset((void *)(RDWR_COMPAT_MPT_VIRT_START +
(i << L2_PAGETABLE_SHIFT)),
- 0x55,
+ 0xFF,
1UL << L2_PAGETABLE_SHIFT);
/* NB. Cannot be GLOBAL as the ptes get copied into per-VM space. */
l2e_write(l2_ro_mpt, l2e_from_page(l1_pg, _PAGE_PSE|_PAGE_PRESENT));
--
2.7.4
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On 27/08/2019 12:48, Igor Druzhinin wrote: > Since guest resource management work it's now possible to have a page > assigned to a domain without a valid M2P entry. Some pathes in the code paths > rely on the fact a GFN returned from mfn_to_gfn() for such a page > is not valid as well, i.e. see arch_iommu_populate_page_table(). > > For systems without 512GB contiguous RAM M2P entries were already > correctly initialized on boot with INVALID_M2P_ENTRY (~0UL) but > on systems where M2P could be covered by a single 1GB page directory > 0x77 poison was used instead. That eventually resulted in a crash > during IOMMU construction on systems without shared PTs enabled. > > While here fixup compat M2P entries as well. > > Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
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