diff options
Diffstat (limited to 'hw/vfio')
| -rw-r--r-- | hw/vfio/common.c | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/hw/vfio/common.c b/hw/vfio/common.c index f8a2fe8..8a9bbf2 100644 --- a/hw/vfio/common.c +++ b/hw/vfio/common.c @@ -36,6 +36,7 @@ #include "qemu/range.h" #include "sysemu/kvm.h" #include "sysemu/reset.h" +#include "sysemu/runstate.h" #include "trace.h" #include "qapi/error.h" #include "migration/migration.h" @@ -569,6 +570,44 @@ static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, error_report("iommu map to non memory area %"HWADDR_PRIx"", xlat); return false; + } else if (memory_region_has_ram_discard_manager(mr)) { + RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr); + MemoryRegionSection tmp = { + .mr = mr, + .offset_within_region = xlat, + .size = int128_make64(len), + }; + + /* + * Malicious VMs can map memory into the IOMMU, which is expected + * to remain discarded. vfio will pin all pages, populating memory. + * Disallow that. vmstate priorities make sure any RamDiscardManager + * were already restored before IOMMUs are restored. + */ + if (!ram_discard_manager_is_populated(rdm, &tmp)) { + error_report("iommu map to discarded memory (e.g., unplugged via" + " virtio-mem): %"HWADDR_PRIx"", + iotlb->translated_addr); + return false; + } + + /* + * Malicious VMs might trigger discarding of IOMMU-mapped memory. The + * pages will remain pinned inside vfio until unmapped, resulting in a + * higher memory consumption than expected. If memory would get + * populated again later, there would be an inconsistency between pages + * pinned by vfio and pages seen by QEMU. This is the case until + * unmapped from the IOMMU (e.g., during device reset). + * + * With malicious guests, we really only care about pinning more memory + * than expected. RLIMIT_MEMLOCK set for the user/process can never be + * exceeded and can be used to mitigate this problem. + */ + warn_report_once("Using vfio with vIOMMUs and coordinated discarding of" + " RAM (e.g., virtio-mem) works, however, malicious" + " guests can trigger pinning of more memory than" + " intended via an IOMMU. It's possible to mitigate " + " by setting/adjusting RLIMIT_MEMLOCK."); } /* |