From 59ad61373f73de6a3eb17e0c1989bc048b51b55c Mon Sep 17 00:00:00 2001
From: Maxime Coquelin <maxime.coquelin@redhat.com>
Date: Fri, 20 Oct 2017 14:17:06 +0200
Subject: [PATCH 04/19] exec: add page_mask for address_space_do_translate

RH-Author: Maxime Coquelin <maxime.coquelin@redhat.com>
Message-id: <20171020141707.17637-2-maxime.coquelin@redhat.com>
Patchwork-id: 77417
O-Subject: [RHV7.5 qemu-kvm-rhev PATCH 1/2] exec: add page_mask for address_space_do_translate
Bugzilla: 1498817
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
RH-Acked-by: Jens Freimann <jfreimann@redhat.com>

From: Peter Xu <peterx@redhat.com>

The function is originally used for address_space_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 address_space_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@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Message-Id: <20171010094247.10173-2-maxime.coquelin@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit d5e5fafd11be4458443c43f19c1ebdd24d99a751)
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

Conflicts:
	exec.c (Skipping 166206845f7f)
---
 exec.c | 32 +++++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/exec.c b/exec.c
index d20c34c..e5f97fd 100644
--- a/exec.c
+++ b/exec.c
@@ -475,7 +475,8 @@ address_space_translate_internal(AddressSpaceDispatch *d, hwaddr addr, hwaddr *x
 static MemoryRegionSection address_space_do_translate(AddressSpace *as,
                                                       hwaddr addr,
                                                       hwaddr *xlat,
-                                                      hwaddr *plen,
+                                                      hwaddr *plen_out,
+                                                      hwaddr *page_mask_out,
                                                       bool is_write,
                                                       bool is_mmio)
 {
@@ -483,10 +484,16 @@ static MemoryRegionSection address_space_do_translate(AddressSpace *as,
     MemoryRegionSection *section;
     IOMMUMemoryRegion *iommu_mr;
     IOMMUMemoryRegionClass *imrc;
+    hwaddr page_mask = (hwaddr)(-1);
+    hwaddr plen = (hwaddr)(-1);
+
+    if (plen_out) {
+        plen = *plen_out;
+    }
 
     for (;;) {
         AddressSpaceDispatch *d = atomic_rcu_read(&as->dispatch);
-        section = address_space_translate_internal(d, addr, &addr, plen, is_mmio);
+        section = address_space_translate_internal(d, addr, &addr, &plen, is_mmio);
 
         iommu_mr = memory_region_get_iommu(section->mr);
         if (!iommu_mr) {
@@ -498,7 +505,8 @@ static MemoryRegionSection address_space_do_translate(AddressSpace *as,
                                 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 +516,19 @@ static MemoryRegionSection address_space_do_translate(AddressSpace *as,
 
     *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 +547,7 @@ IOMMUTLBEntry address_space_get_iotlb_entry(AddressSpace *as, hwaddr addr,
 
     /* This can never be MMIO. */
     section = address_space_do_translate(as, addr, &xlat, &plen,
-                                         is_write, false);
+                                         NULL, is_write, false);
 
     /* Illegal translation */
     if (section.mr == &io_mem_unassigned) {
@@ -570,7 +591,8 @@ MemoryRegion *address_space_translate(AddressSpace *as, hwaddr addr,
     MemoryRegionSection section;
 
     /* This can be MMIO, so setup MMIO bit. */
-    section = address_space_do_translate(as, addr, xlat, plen, is_write, true);
+    section = address_space_do_translate(as, addr, xlat, plen, NULL,
+                                         is_write, true);
     mr = section.mr;
 
     if (xen_enabled() && memory_access_is_direct(mr, is_write)) {
-- 
1.8.3.1