[Xen-devel] [PATCH 2/2] libxc: add MMIO hole size parameter to xc_hvm_build()

[David Vrabel <david.vrabel@xxxxxxxxxx>]

From: David Vrabel <david.vrabel@xxxxxxxxxx>

Add a parameter for the MMIO hole size when building a HVM domain.

This is useful for specifying a larger than normal MMIO hole to ensure
that no PCI device's MMIO region overlaps with the guest physical
addresses of RAM.  This is needed on certain systems with PCI bridges
with ACS versions that are broken.  On these systems, if a device
behind the bridge attempts a DMA to a guest physical address that
overlaps with the MMIO region of another device behind the bridge,
then the bridge intercepts the access and forwards it directly to the
device and the read or write never hits RAM.

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
 tools/libxc/xc_hvm_build.c |   29 ++++++++++++++++++-----------
 tools/libxc/xenguest.h     |    1 +
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/tools/libxc/xc_hvm_build.c b/tools/libxc/xc_hvm_build.c
index 31d4734..fbeddac 100644
--- a/tools/libxc/xc_hvm_build.c
+++ b/tools/libxc/xc_hvm_build.c
@@ -46,7 +46,8 @@
 #define NR_SPECIAL_PAGES     5
 #define special_pfn(x) (0xff000u - NR_SPECIAL_PAGES + (x))
 
-static void build_hvm_info(void *hvm_info_page, uint64_t mem_size)
+static void build_hvm_info(void *hvm_info_page, uint64_t mem_size,
+                           uint64_t mmio_start, uint64_t mmio_size)
 {
     struct hvm_info_table *hvm_info = (struct hvm_info_table *)
         (((unsigned char *)hvm_info_page) + HVM_INFO_OFFSET);
@@ -54,10 +55,10 @@ static void build_hvm_info(void *hvm_info_page, uint64_t 
mem_size)
     uint8_t sum;
     int i;
 
-    if ( lowmem_end > HVM_BELOW_4G_RAM_END )
+    if ( lowmem_end > mmio_start )
     {
-        highmem_end = lowmem_end + (1ull<<32) - HVM_BELOW_4G_RAM_END;
-        lowmem_end = HVM_BELOW_4G_RAM_END;
+        highmem_end = (1ull<<32) + (lowmem_end - mmio_start);
+        lowmem_end = mmio_start;
     }
 
     memset(hvm_info_page, 0, PAGE_SIZE);
@@ -126,10 +127,10 @@ static int loadelfimage(
  * Check whether there exists mmio hole in the specified memory range.
  * Returns 1 if exists, else returns 0.
  */
-static int check_mmio_hole(uint64_t start, uint64_t memsize)
+static int check_mmio_hole(uint64_t start, uint64_t memsize,
+                           uint64_t mmio_start, uint64_t mmio_size)
 {
-    if ( start + memsize <= HVM_BELOW_4G_MMIO_START ||
-         start >= HVM_BELOW_4G_MMIO_START + HVM_BELOW_4G_MMIO_LENGTH )
+    if ( start + memsize <= mmio_start || start >= mmio_start + mmio_size )
         return 0;
     else
         return 1;
@@ -142,6 +143,8 @@ static int setup_guest(xc_interface *xch,
     xen_pfn_t *page_array = NULL;
     unsigned long i, nr_pages = params->mem_size >> PAGE_SHIFT;
     unsigned long target_pages = params->mem_target >> PAGE_SHIFT;
+    uint64_t mmio_start = (1ull << 32) - params->mmio_size;
+    uint64_t mmio_size = params->mmio_size;
     unsigned long entry_eip, cur_pages, cur_pfn;
     void *hvm_info_page;
     uint32_t *ident_pt;
@@ -188,8 +191,8 @@ static int setup_guest(xc_interface *xch,
 
     for ( i = 0; i < nr_pages; i++ )
         page_array[i] = i;
-    for ( i = HVM_BELOW_4G_RAM_END >> PAGE_SHIFT; i < nr_pages; i++ )
-        page_array[i] += HVM_BELOW_4G_MMIO_LENGTH >> PAGE_SHIFT;
+    for ( i = mmio_start >> PAGE_SHIFT; i < nr_pages; i++ )
+        page_array[i] += mmio_size >> PAGE_SHIFT;
 
     /*
      * Allocate memory for HVM guest, skipping VGA hole 0xA0000-0xC0000.
@@ -230,7 +233,8 @@ static int setup_guest(xc_interface *xch,
         if ( ((count | cur_pfn) & (SUPERPAGE_1GB_NR_PFNS - 1)) == 0 &&
              /* Check if there exists MMIO hole in the 1GB memory range */
              !check_mmio_hole(cur_pfn << PAGE_SHIFT,
-                              SUPERPAGE_1GB_NR_PFNS << PAGE_SHIFT) )
+                              SUPERPAGE_1GB_NR_PFNS << PAGE_SHIFT,
+                              mmio_start, mmio_size) )
         {
             long done;
             unsigned long nr_extents = count >> SUPERPAGE_1GB_SHIFT;
@@ -327,7 +331,7 @@ static int setup_guest(xc_interface *xch,
               xch, dom, PAGE_SIZE, PROT_READ | PROT_WRITE,
               HVM_INFO_PFN)) == NULL )
         goto error_out;
-    build_hvm_info(hvm_info_page, v_end);
+    build_hvm_info(hvm_info_page, v_end, mmio_start, mmio_size);
     munmap(hvm_info_page, PAGE_SIZE);
 
     /* Allocate and clear special pages. */
@@ -408,6 +412,9 @@ int xc_hvm_build(xc_interface *xch, uint32_t domid,
     if ( params.mem_target == 0 )
         params.mem_target = params.mem_size;
 
+    if ( params.mmio_size == 0 )
+        params.mmio_size = HVM_BELOW_4G_MMIO_LENGTH;
+
     /* An HVM guest must be initialised with at least 2MB memory. */
     if ( params.mem_size < (2ull << 20) || params.mem_target < (2ull << 20) )
         return -1;
diff --git a/tools/libxc/xenguest.h b/tools/libxc/xenguest.h
index 19b0382..b06788c 100644
--- a/tools/libxc/xenguest.h
+++ b/tools/libxc/xenguest.h
@@ -174,6 +174,7 @@ int xc_linux_build_mem(xc_interface *xch,
 struct xc_hvm_params {
     uint64_t mem_size;           /**< Memory size in bytes. */
     uint64_t mem_target;         /**< Memory target in bytes. */
+    uint64_t mmio_size;          /**< Size of the MMIO hole in bytes. */
     const char *image_file_name; /**< File name of the image to load. */
 };
 
-- 
1.7.2.5


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