[PATCH v3] memory: Optimize replay of guest mapping

* [PATCH v3] memory: Optimize replay of guest mapping
@ 2023-04-13 11:00 Zhenzhong Duan
  2023-04-13 18:53 ` Peter Xu
  2023-04-18 10:13 ` Peter Maydell
  0 siblings, 2 replies; 6+ messages in thread
From: Zhenzhong Duan @ 2023-04-13 11:00 UTC (permalink / raw)
  To: qemu-devel
  Cc: mst, peterx, jasowang, marcel.apfelbaum, pbonzini,
	richard.henderson, eduardo, david, philmd, peter.maydell

On x86, there are two notifiers registered due to vtd-ir memory
region splitting the entire address space. During replay of the
address space for each notifier, the whole address space is
scanned which is unnecessary. We only need to scan the space
belong to notifier monitored space.

While on x86 IOMMU memory region spans over entire address space,
but on some other platforms(e.g. arm mps3-an547), IOMMU memory
region is only a window in the whole address space. user could
register a notifier with arbitrary scope beyond IOMMU memory
region. Though in current implementation replay is only triggered
by VFIO and dirty page sync with notifiers derived from memory
region section, but this isn't guaranteed in the future.

So, we replay the intersection part of IOMMU memory region and
IOMMU notifier in memory_region_iommu_replay().

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
v3: Fix assert failure on mps3-an547
v2: Add an assert per Peter
Tested on x86 with a net card passed to guest(kvm/tcg), ping/ssh pass.
Also did simple bootup test with mps3-an547

 hw/i386/intel_iommu.c | 2 +-
 softmmu/memory.c      | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index a62896759c78..faade7def867 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -3850,7 +3850,7 @@ static void vtd_iommu_replay(IOMMUMemoryRegion *iommu_mr, IOMMUNotifier *n)
                 .domain_id = vtd_get_domain_id(s, &ce, vtd_as->pasid),
             };
 
-            vtd_page_walk(s, &ce, 0, ~0ULL, &info, vtd_as->pasid);
+            vtd_page_walk(s, &ce, n->start, n->end, &info, vtd_as->pasid);
         }
     } else {
         trace_vtd_replay_ce_invalid(bus_n, PCI_SLOT(vtd_as->devfn),
diff --git a/softmmu/memory.c b/softmmu/memory.c
index b1a6cae6f583..f7af691991de 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -1925,7 +1925,7 @@ void memory_region_iommu_replay(IOMMUMemoryRegion *iommu_mr, IOMMUNotifier *n)
 {
     MemoryRegion *mr = MEMORY_REGION(iommu_mr);
     IOMMUMemoryRegionClass *imrc = IOMMU_MEMORY_REGION_GET_CLASS(iommu_mr);
-    hwaddr addr, granularity;
+    hwaddr addr, end, granularity;
     IOMMUTLBEntry iotlb;
 
     /* If the IOMMU has its own replay callback, override */
@@ -1935,8 +1935,9 @@ void memory_region_iommu_replay(IOMMUMemoryRegion *iommu_mr, IOMMUNotifier *n)
     }
 
     granularity = memory_region_iommu_get_min_page_size(iommu_mr);
+    end = MIN(n->end, memory_region_size(mr));
 
-    for (addr = 0; addr < memory_region_size(mr); addr += granularity) {
+    for (addr = n->start; addr < end; addr += granularity) {
         iotlb = imrc->translate(iommu_mr, addr, IOMMU_NONE, n->iommu_idx);
         if (iotlb.perm != IOMMU_NONE) {
             n->notify(n, &iotlb);
-- 
2.25.1



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