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[Xen-devel] [PATCH v3 1/1] Add pci_hole_min_size



If you add enough PCI devices then all mmio may not fit below 4G
which may not be the layout the user wanted. This allows you to
increase the below 4G address space that PCI devices can use and
therefore in more cases not have any mmio that is above 4G.

There are real PCI cards that do not support mmio over 4G, so if you
want to emulate them precisely, you may also need to increase the
space below 4G for them. There are drivers for these cards that also
do not work if they have their mmio space mapped above 4G.

This allows growing the pci_hole to the size needed.

This may help with using pci passthru and HVM.

Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
---
v3:
  Dropped "if (dom_info.debug)" in parse_config_data()
  since dom_info no long passed in.

  Lots more bounds checking.  Since QEMU is a min(qemu_limit,
  max_ram_below_4g) adjust code the do the same.

  More in commit message.

 docs/man/xl.cfg.pod.5             | 12 ++++++++++++
 tools/firmware/hvmloader/config.h |  1 -
 tools/firmware/hvmloader/pci.c    | 28 +++++++++++++++++++++++++++-
 tools/libxc/xc_hvm_build_x86.c    | 30 ++++++++++++++++++++++++++++--
 tools/libxc/xenguest.h            | 11 +++++++++++
 tools/libxl/libxl_create.c        | 29 ++++++++++++++++++++++-------
 tools/libxl/libxl_dm.c            | 23 +++++++++++++++++++++--
 tools/libxl/libxl_dom.c           |  3 ++-
 tools/libxl/libxl_types.idl       |  1 +
 tools/libxl/xl_cmdimpl.c          | 13 +++++++++++++
 10 files changed, 137 insertions(+), 14 deletions(-)

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index c087cbc..60b4cb6 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -1032,6 +1032,18 @@ wallclock (i.e., real) time.
 
 =back
 
+=head3 Memory layout
+
+=over 4
+
+=item B<pci_hole_min_size=BYTES>
+
+Specifies the minimum size the PCI MMIO hole below 4GiB will be.
+Only valid for device_model_version = "qemu-xen".
+Note: this requires QEMU 2.1.0 or later.
+
+=back
+
 =head3 Support for Paravirtualisation of HVM Guests
 
 The following options allow Paravirtualised features (such as devices)
diff --git a/tools/firmware/hvmloader/config.h 
b/tools/firmware/hvmloader/config.h
index 80bea46..b838cf9 100644
--- a/tools/firmware/hvmloader/config.h
+++ b/tools/firmware/hvmloader/config.h
@@ -53,7 +53,6 @@ extern struct bios_config ovmf_config;
 #define PCI_ISA_IRQ_MASK    0x0c20U /* ISA IRQs 5,10,11 are PCI connected */
 
 /* MMIO hole: Hardcoded defaults, which can be dynamically expanded. */
-#define PCI_MEM_START       0xf0000000
 #define PCI_MEM_END         0xfc000000
 
 extern unsigned long pci_mem_start, pci_mem_end;
diff --git a/tools/firmware/hvmloader/pci.c b/tools/firmware/hvmloader/pci.c
index 3712988..dff3576 100644
--- a/tools/firmware/hvmloader/pci.c
+++ b/tools/firmware/hvmloader/pci.c
@@ -28,9 +28,10 @@
 #include <xen/memory.h>
 #include <xen/hvm/ioreq.h>
 #include <xen/hvm/hvm_xs_strings.h>
+#include <xen/hvm/e820.h>
 #include <stdbool.h>
 
-unsigned long pci_mem_start = PCI_MEM_START;
+unsigned long pci_mem_start = HVM_BELOW_4G_RAM_END;
 unsigned long pci_mem_end = PCI_MEM_END;
 uint64_t pci_hi_mem_start = 0, pci_hi_mem_end = 0;
 
@@ -59,6 +60,7 @@ void pci_setup(void)
         uint64_t bar_sz;
     } *bars = (struct bars *)scratch_start;
     unsigned int i, nr_bars = 0;
+    uint64_t pci_hole_min_size = 0;
 
     const char *s;
     /*
@@ -86,6 +88,10 @@ void pci_setup(void)
     printf("Relocating guest memory for lowmem MMIO space %s\n",
            allow_memory_relocate?"enabled":"disabled");
 
+    s = xenstore_read("platform/pci_hole_min_size", NULL);
+    if ( s )
+        pci_hole_min_size = strtoll(s, NULL, 0);
+
     /* Program PCI-ISA bridge with appropriate link routes. */
     isa_irq = 0;
     for ( link = 0; link < 4; link++ )
@@ -237,6 +243,26 @@ void pci_setup(void)
         pci_writew(devfn, PCI_COMMAND, cmd);
     }
 
+    if ( pci_hole_min_size )
+    {
+        uint64_t max_ram_below_4g = (1ULL << 32) - pci_hole_min_size;
+
+        if ( max_ram_below_4g >= HVM_BELOW_4G_RAM_END )
+        {
+            printf("max_ram_below_4g=0x"PRIllx
+                   " too big for pci_hole_min_size=0x"PRIllx"\n",
+                   PRIllx_arg(max_ram_below_4g),
+                   PRIllx_arg(pci_hole_min_size));
+        }
+        else
+        {
+            pci_mem_start = max_ram_below_4g;
+            printf("pci_mem_start=0x%lx (was 0x%x) for 
pci_hole_min_size=%lu\n",
+                   pci_mem_start, HVM_BELOW_4G_RAM_END,
+                   (long)pci_hole_min_size);
+        }
+    }
+
     /*
      * At the moment qemu-xen can't deal with relocated memory regions.
      * It's too close to the release to make a proper fix; for now,
diff --git a/tools/libxc/xc_hvm_build_x86.c b/tools/libxc/xc_hvm_build_x86.c
index ed1069b..f557f87 100644
--- a/tools/libxc/xc_hvm_build_x86.c
+++ b/tools/libxc/xc_hvm_build_x86.c
@@ -628,14 +628,40 @@ int xc_hvm_build_target_mem(xc_interface *xch,
                            int target,
                            const char *image_name)
 {
+    return xc_hvm_build_target_mem_with_hole(xch, domid, memsize, target,
+                                             image_name, 0);
+}
+
+int xc_hvm_build_with_hole(xc_interface *xch, uint32_t domid,
+                           struct xc_hvm_build_args *args,
+                           uint64_t pci_hole_min_size)
+{
+    if (pci_hole_min_size)
+    {
+        uint64_t max_ram_below_4g = (1ULL << 32) - pci_hole_min_size;
+
+        if (max_ram_below_4g < HVM_BELOW_4G_RAM_END)
+        {
+            args->mmio_size = pci_hole_min_size;
+        }
+    }
+    return xc_hvm_build(xch, domid, args);
+}
+
+int xc_hvm_build_target_mem_with_hole(xc_interface *xch,
+                                      uint32_t domid,
+                                      int memsize,
+                                      int target,
+                                      const char *image_name,
+                                      uint64_t pci_hole_min_size)
+{
     struct xc_hvm_build_args args = {};
 
     memset(&args, 0, sizeof(struct xc_hvm_build_args));
     args.mem_size = (uint64_t)memsize << 20;
     args.mem_target = (uint64_t)target << 20;
     args.image_file_name = image_name;
-
-    return xc_hvm_build(xch, domid, &args);
+    return xc_hvm_build_with_hole(xch, domid, &args, pci_hole_min_size);
 }
 
 /*
diff --git a/tools/libxc/xenguest.h b/tools/libxc/xenguest.h
index 1f216cd..0e9c5f0 100644
--- a/tools/libxc/xenguest.h
+++ b/tools/libxc/xenguest.h
@@ -248,12 +248,23 @@ struct xc_hvm_build_args {
 int xc_hvm_build(xc_interface *xch, uint32_t domid,
                  struct xc_hvm_build_args *hvm_args);
 
+int xc_hvm_build_with_hole(xc_interface *xch, uint32_t domid,
+                           struct xc_hvm_build_args *args,
+                           uint64_t pci_hole_min_size);
+
 int xc_hvm_build_target_mem(xc_interface *xch,
                             uint32_t domid,
                             int memsize,
                             int target,
                             const char *image_name);
 
+int xc_hvm_build_target_mem_with_hole(xc_interface *xch,
+                                      uint32_t domid,
+                                      int memsize,
+                                      int target,
+                                      const char *image_name,
+                                      uint64_t pci_hole_min_size);
+
 /*
  * Sets *lockfd to -1.
  * Has deallocated everything even on error.
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index d6b8a29..b90d787 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -23,6 +23,7 @@
 #include <xc_dom.h>
 #include <xenguest.h>
 #include <xen/hvm/hvm_info_table.h>
+#include <xen/hvm/e820.h>
 
 int libxl__domain_create_info_setdefault(libxl__gc *gc,
                                          libxl_domain_create_info *c_info)
@@ -402,13 +403,26 @@ int libxl__domain_build(libxl__gc *gc,
         vments[4] = "start_time";
         vments[5] = libxl__sprintf(gc, "%lu.%02d", 
start_time.tv_sec,(int)start_time.tv_usec/10000);
 
-        localents = libxl__calloc(gc, 7, sizeof(char *));
-        localents[0] = "platform/acpi";
-        localents[1] = libxl_defbool_val(info->u.hvm.acpi) ? "1" : "0";
-        localents[2] = "platform/acpi_s3";
-        localents[3] = libxl_defbool_val(info->u.hvm.acpi_s3) ? "1" : "0";
-        localents[4] = "platform/acpi_s4";
-        localents[5] = libxl_defbool_val(info->u.hvm.acpi_s4) ? "1" : "0";
+        localents = libxl__calloc(gc, 9, sizeof(char *));
+        i = 0;
+        localents[i++] = "platform/acpi";
+        localents[i++] = libxl_defbool_val(info->u.hvm.acpi) ? "1" : "0";
+        localents[i++] = "platform/acpi_s3";
+        localents[i++] = libxl_defbool_val(info->u.hvm.acpi_s3) ? "1" : "0";
+        localents[i++] = "platform/acpi_s4";
+        localents[i++] = libxl_defbool_val(info->u.hvm.acpi_s4) ? "1" : "0";
+        if (info->u.hvm.pci_hole_min_size) {
+            uint64_t max_ram_below_4g =
+                (1ULL << 32) - info->u.hvm.pci_hole_min_size;
+
+            if (max_ram_below_4g < HVM_BELOW_4G_RAM_END) {
+                localents[i++] = "platform/pci_hole_min_size";
+                localents[i++] =
+                    libxl__sprintf(gc, "%"PRIu64,
+                                   info->u.hvm.pci_hole_min_size);
+            }
+        }
+        assert(i < 9);
 
         break;
     case LIBXL_DOMAIN_TYPE_PV:
@@ -434,6 +448,7 @@ int libxl__domain_build(libxl__gc *gc,
             vments[i++] = "image/cmdline";
             vments[i++] = (char *) state->pv_cmdline;
         }
+        assert(i < 11);
 
         break;
     default:
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index addacdb..147e682 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -18,6 +18,7 @@
 #include "libxl_osdeps.h" /* must come before any other headers */
 
 #include "libxl_internal.h"
+#include <xen/hvm/e820.h>
 
 static const char *libxl_tapif_script(libxl__gc *gc)
 {
@@ -393,6 +394,7 @@ static char ** libxl__build_device_model_args_new(libxl__gc 
*gc,
     const libxl_vnc_info *vnc = libxl__dm_vnc(guest_config);
     const libxl_sdl_info *sdl = dm_sdl(guest_config);
     const char *keymap = dm_keymap(guest_config);
+    char *machinearg;
     flexarray_t *dm_args;
     int i;
     uint64_t ram_size;
@@ -658,10 +660,27 @@ static char ** 
libxl__build_device_model_args_new(libxl__gc *gc,
             /* Switching here to the machine "pc" which does not add
              * the xen-platform device instead of the default "xenfv" machine.
              */
-            flexarray_append(dm_args, "pc,accel=xen");
+            machinearg = libxl__sprintf(gc, "pc,accel=xen");
         } else {
-            flexarray_append(dm_args, "xenfv");
+            machinearg = libxl__sprintf(gc, "xenfv");
         }
+        if (b_info->u.hvm.pci_hole_min_size) {
+            uint64_t max_ram_below_4g = (1ULL << 32) -
+                b_info->u.hvm.pci_hole_min_size;
+
+            if (max_ram_below_4g >= HVM_BELOW_4G_RAM_END) {
+                LIBXL__LOG(ctx, LIBXL__LOG_WARNING,
+                           "pci_hole_min_size(%"PRIu64
+                           ") too big => max-ram-below-4g=%"PRIu64
+                           " >= %u ignored.\n",
+                           b_info->u.hvm.pci_hole_min_size,
+                           max_ram_below_4g, HVM_BELOW_4G_RAM_END);
+            } else {
+                machinearg = libxl__sprintf(gc, "%s,max-ram-below-4g=%"PRIu64,
+                                            machinearg, max_ram_below_4g);
+            }
+        }
+        flexarray_append(dm_args, machinearg);
         for (i = 0; b_info->extra_hvm && b_info->extra_hvm[i] != NULL; i++)
             flexarray_append(dm_args, b_info->extra_hvm[i]);
         break;
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 661999c..b8559ea 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -655,7 +655,8 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
         goto out;
     }
 
-    ret = xc_hvm_build(ctx->xch, domid, &args);
+    ret = xc_hvm_build_with_hole(ctx->xch, domid, &args,
+                                 info->u.hvm.pci_hole_min_size);
     if (ret) {
         LOGEV(ERROR, ret, "hvm building failed");
         goto out;
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 1018142..3b72565 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -351,6 +351,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
                                        ("timeoffset",       string),
                                        ("hpet",             libxl_defbool),
                                        ("vpt_align",        libxl_defbool),
+                                       ("pci_hole_min_size",UInt(64, init_val 
= 0)),
                                        ("timer_mode",       libxl_timer_mode),
                                        ("nested_hvm",       libxl_defbool),
                                        ("smbios_firmware",  string),
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index be041f2..3c1fc47 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -34,6 +34,7 @@
 #include <ctype.h>
 #include <inttypes.h>
 #include <limits.h>
+#include <xen/hvm/e820.h>
 
 #include "libxl.h"
 #include "libxl_utils.h"
@@ -969,6 +970,18 @@ static void parse_config_data(const char *config_source,
         xlu_cfg_get_defbool(config, "hpet", &b_info->u.hvm.hpet, 0);
         xlu_cfg_get_defbool(config, "vpt_align", &b_info->u.hvm.vpt_align, 0);
 
+        if (!xlu_cfg_get_long(config, "pci_hole_min_size", &l, 0)) {
+            b_info->u.hvm.pci_hole_min_size = (uint64_t) l;
+            if (b_info->u.hvm.pci_hole_min_size < HVM_BELOW_4G_MMIO_LENGTH ||
+                b_info->u.hvm.pci_hole_min_size > HVM_BELOW_4G_RAM_END) {
+                fprintf(stderr, "ERROR: invalid value 0x%"PRIx64" (%"PRIu64
+                        ") for \"pci_hole_min_size\"\n",
+                        b_info->u.hvm.pci_hole_min_size,
+                        b_info->u.hvm.pci_hole_min_size);
+                exit (1);
+            }
+        }
+
         if (!xlu_cfg_get_long(config, "timer_mode", &l, 1)) {
             const char *s = libxl_timer_mode_to_string(l);
             fprintf(stderr, "WARNING: specifying \"timer_mode\" as an integer 
is deprecated. "
-- 
1.8.4


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