| Message ID | 20230908142136.403541-14-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | virtio-mem: Expose device memory through multiple memslots | expand |
On 8.09.2023 16:21, David Hildenbrand wrote: > We really only care about the RAM memory region not being mapped into > an address space yet as long as we're still setting up the > RamDiscardManager. Once mapped into an address space, memory notifiers > would get notified about such a region and any attempts to modify the > RamDiscardManager would be wrong. > > While "mapped into an address space" is easy to check for RAM regions that > are mapped directly (following the ->container links), it's harder to > check when such regions are mapped indirectly via aliases. For now, we can > only detect that a region is mapped through an alias (->mapped_via_alias), > but we don't have a handle on these aliases to follow all their ->container > links to test if they are eventually mapped into an address space. > > So relax the assertion in memory_region_set_ram_discard_manager(), > remove the check in memory_region_get_ram_discard_manager() and clarify > the doc. > > Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com> Thanks, Maciej
diff --git a/include/exec/memory.h b/include/exec/memory.h index 68284428f8..5feb704585 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -593,8 +593,9 @@ typedef void (*ReplayRamDiscard)(MemoryRegionSection *section, void *opaque); * populated (consuming memory), to be used/accessed by the VM. * * A #RamDiscardManager can only be set for a RAM #MemoryRegion while the - * #MemoryRegion isn't mapped yet; it cannot change while the #MemoryRegion is - * mapped. + * #MemoryRegion isn't mapped into an address space yet (either directly + * or via an alias); it cannot change while the #MemoryRegion is + * mapped into an address space. * * The #RamDiscardManager is intended to be used by technologies that are * incompatible with discarding of RAM (e.g., VFIO, which may pin all diff --git a/softmmu/memory.c b/softmmu/memory.c index 7d9494ce70..c1e8aa133f 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -2081,7 +2081,7 @@ int memory_region_iommu_num_indexes(IOMMUMemoryRegion *iommu_mr) RamDiscardManager *memory_region_get_ram_discard_manager(MemoryRegion *mr) { - if (!memory_region_is_mapped(mr) || !memory_region_is_ram(mr)) { + if (!memory_region_is_ram(mr)) { return NULL; } return mr->rdm; @@ -2090,7 +2090,7 @@ RamDiscardManager *memory_region_get_ram_discard_manager(MemoryRegion *mr) void memory_region_set_ram_discard_manager(MemoryRegion *mr, RamDiscardManager *rdm) { - g_assert(memory_region_is_ram(mr) && !memory_region_is_mapped(mr)); + g_assert(memory_region_is_ram(mr)); g_assert(!rdm || !mr->rdm); mr->rdm = rdm; }
We really only care about the RAM memory region not being mapped into an address space yet as long as we're still setting up the RamDiscardManager. Once mapped into an address space, memory notifiers would get notified about such a region and any attempts to modify the RamDiscardManager would be wrong. While "mapped into an address space" is easy to check for RAM regions that are mapped directly (following the ->container links), it's harder to check when such regions are mapped indirectly via aliases. For now, we can only detect that a region is mapped through an alias (->mapped_via_alias), but we don't have a handle on these aliases to follow all their ->container links to test if they are eventually mapped into an address space. So relax the assertion in memory_region_set_ram_discard_manager(), remove the check in memory_region_get_ram_discard_manager() and clarify the doc. Signed-off-by: David Hildenbrand <david@redhat.com> --- include/exec/memory.h | 5 +++-- softmmu/memory.c | 4 ++-- 2 files changed, 5 insertions(+), 4 deletions(-)