[Xen-changelog] [qemu-xen stable-4.10] exec: add page_mask for flatview_do_translate

[patchbot@xxxxxxx]

commit c9dbe3e0fcf704395e35b0ec1cb48041e8c2ea92
Author:     Peter Xu <peterx@xxxxxxxxxx>
AuthorDate: Tue Oct 10 11:42:45 2017 +0200
Commit:     Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon Dec 4 22:42:28 2017 -0600

    exec: add page_mask for flatview_do_translate
    
    The function is originally used for flatview_space_translate() and what
    we care about most is (xlat, plen) range. However for iotlb requests, we
    don't really care about "plen", but the size of the page that "xlat" is
    located on. While, plen cannot really contain this information.
    
    A simple example to show why "plen" is not good for IOTLB translations:
    
    E.g., for huge pages, it is possible that guest mapped 1G huge page on
    device side that used this GPA range:
    
      0x100000000 - 0x13fffffff
    
    Then let's say we want to translate one IOVA that finally mapped to GPA
    0x13ffffe00 (which is located on this 1G huge page). Then here we'll
    get:
    
      (xlat, plen) = (0x13fffe00, 0x200)
    
    So the IOTLB would be only covering a very small range since from
    "plen" (which is 0x200 bytes) we cannot tell the size of the page.
    
    Actually we can really know that this is a huge page - we just throw the
    information away in flatview_do_translate().
    
    This patch introduced "page_mask" optional parameter to capture that
    page mask info. Also, I made "plen" an optional parameter as well, with
    some comments for the whole function.
    
    No functional change yet.
    
    Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
    Signed-off-by: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx>
    Message-Id: <20171010094247.10173-2-maxime.coquelin@xxxxxxxxxx>
    Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    (cherry picked from commit d5e5fafd11be4458443c43f19c1ebdd24d99a751)
    Signed-off-by: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
---
 exec.c | 51 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 6 deletions(-)

diff --git a/exec.c b/exec.c
index b1f29d3..2fd65dc 100644
--- a/exec.c
+++ b/exec.c
@@ -468,11 +468,29 @@ address_space_translate_internal(AddressSpaceDispatch *d, 
hwaddr addr, hwaddr *x
     return section;
 }
 
-/* Called from RCU critical section */
+/**
+ * flatview_do_translate - translate an address in FlatView
+ *
+ * @fv: the flat view that we want to translate on
+ * @addr: the address to be translated in above address space
+ * @xlat: the translated address offset within memory region. It
+ *        cannot be @NULL.
+ * @plen_out: valid read/write length of the translated address. It
+ *            can be @NULL when we don't care about it.
+ * @page_mask_out: page mask for the translated address. This
+ *            should only be meaningful for IOMMU translated
+ *            addresses, since there may be huge pages that this bit
+ *            would tell. It can be @NULL if we don't care about it.
+ * @is_write: whether the translation operation is for write
+ * @is_mmio: whether this can be MMIO, set true if it can
+ *
+ * This function is called from RCU critical section
+ */
 static MemoryRegionSection flatview_do_translate(FlatView *fv,
                                                  hwaddr addr,
                                                  hwaddr *xlat,
-                                                 hwaddr *plen,
+                                                 hwaddr *plen_out,
+                                                 hwaddr *page_mask_out,
                                                  bool is_write,
                                                  bool is_mmio,
                                                  AddressSpace **target_as)
@@ -481,11 +499,17 @@ static MemoryRegionSection flatview_do_translate(FlatView 
*fv,
     MemoryRegionSection *section;
     IOMMUMemoryRegion *iommu_mr;
     IOMMUMemoryRegionClass *imrc;
+    hwaddr page_mask = (hwaddr)(-1);
+    hwaddr plen = (hwaddr)(-1);
+
+    if (plen_out) {
+        plen = *plen_out;
+    }
 
     for (;;) {
         section = address_space_translate_internal(
                 flatview_to_dispatch(fv), addr, &addr,
-                plen, is_mmio);
+                &plen, is_mmio);
 
         iommu_mr = memory_region_get_iommu(section->mr);
         if (!iommu_mr) {
@@ -497,7 +521,8 @@ static MemoryRegionSection flatview_do_translate(FlatView 
*fv,
                                 IOMMU_WO : IOMMU_RO);
         addr = ((iotlb.translated_addr & ~iotlb.addr_mask)
                 | (addr & iotlb.addr_mask));
-        *plen = MIN(*plen, (addr | iotlb.addr_mask) - addr + 1);
+        page_mask &= iotlb.addr_mask;
+        plen = MIN(plen, (addr | iotlb.addr_mask) - addr + 1);
         if (!(iotlb.perm & (1 << is_write))) {
             goto translate_fail;
         }
@@ -508,6 +533,19 @@ static MemoryRegionSection flatview_do_translate(FlatView 
*fv,
 
     *xlat = addr;
 
+    if (page_mask == (hwaddr)(-1)) {
+        /* Not behind an IOMMU, use default page size. */
+        page_mask = ~TARGET_PAGE_MASK;
+    }
+
+    if (page_mask_out) {
+        *page_mask_out = page_mask;
+    }
+
+    if (plen_out) {
+        *plen_out = plen;
+    }
+
     return *section;
 
 translate_fail:
@@ -526,7 +564,7 @@ IOMMUTLBEntry address_space_get_iotlb_entry(AddressSpace 
*as, hwaddr addr,
 
     /* This can never be MMIO. */
     section = flatview_do_translate(address_space_to_flatview(as), addr,
-                                    &xlat, &plen, is_write, false, &as);
+                                    &xlat, &plen, NULL, is_write, false, &as);
 
     /* Illegal translation */
     if (section.mr == &io_mem_unassigned) {
@@ -570,7 +608,8 @@ MemoryRegion *flatview_translate(FlatView *fv, hwaddr addr, 
hwaddr *xlat,
     AddressSpace *as = NULL;
 
     /* This can be MMIO, so setup MMIO bit. */
-    section = flatview_do_translate(fv, addr, xlat, plen, is_write, true, &as);
+    section = flatview_do_translate(fv, addr, xlat, plen, NULL,
+                                    is_write, true, &as);
     mr = section.mr;
 
     if (xen_enabled() && memory_access_is_direct(mr, is_write)) {
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#stable-4.10

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