Re: [Xen-devel] [v5][PATCH 12/16] tools: introduce a new parameter to set a predefined rdm boundary

[Wei Liu]

On Tue, Jul 07, 2015 at 02:17:13PM +0800, Tiejun Chen wrote:
> Previously we always fix that predefined boundary as 2G to handle
> conflict between memory and rdm, but now this predefined boundar
> can be changes with the parameter "rdm_mem_boundary" in .cfg file.
> 
> CC: Ian Jackson 
> CC: Stefano Stabellini 
> CC: Ian Campbell 
> CC: Wei Liu 
> Signed-off-by: Tiejun Chen 

Acked-by: Wei Liu 

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[Xen-devel] [v5][PATCH 12/16] tools: introduce a new parameter to set a predefined rdm boundary

[Tiejun Chen]

Previously we always fix that predefined boundary as 2G to handle
conflict between memory and rdm, but now this predefined boundar
can be changes with the parameter "rdm_mem_boundary" in .cfg file.

CC: Ian Jackson 
CC: Stefano Stabellini 
CC: Ian Campbell 
CC: Wei Liu 
Signed-off-by: Tiejun Chen 
---
v5:

* Make this variable "rdm_mem_boundary_memkb" specific to .hvm 

v4:

* Separated from the previous patch to provide a parameter to set that
  predefined boundary dynamically.

 docs/man/xl.cfg.pod.5   | 22 ++
 tools/libxl/libxl.h |  6 ++
 tools/libxl/libxl_create.c  |  4 
 tools/libxl/libxl_dom.c |  8 +---
 tools/libxl/libxl_types.idl |  1 +
 tools/libxl/xl_cmdimpl.c|  3 +++
 6 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index a2dc343..d1ba590 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -870,6 +870,28 @@ More information about Xen gfx_passthru feature is 
available
 on the XenVGAPassthrough L
 wiki page.
 
+=item B
+
+Number of megabytes to set a boundary for checking rdm conflict.
+
+When RDM conflicts with RAM, RDM probably scatter the whole RAM space.
+Especially multiple RDM entries would worsen this to lead a complicated
+memory layout. So here we're trying to figure out a simple solution to
+avoid breaking existing layout. So when a conflict occurs,
+
+#1. Above a predefined boundary
+- move lowmem_end below reserved region to solve conflict;
+
+#2. Below a predefined boundary
+- Check strict/relaxed policy.
+"strict" policy leads to fail libxl. Note when both policies
+are specified on a given region, 'strict' is always preferred.
+"relaxed" policy issue a warning message and also mask this
+entry INVALID to indicate we shouldn't expose this entry to
+hvmloader.
+
+Here the default is 2G.
+
 =item B
 
 Specifies the host device tree nodes to passthrough to this guest. Each
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index a1c5d15..6f157c9 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -863,6 +863,12 @@ const char *libxl_defbool_to_string(libxl_defbool b);
 #define LIBXL_TIMER_MODE_DEFAULT -1
 #define LIBXL_MEMKB_DEFAULT ~0ULL
 
+/*
+ * We'd like to set a memory boundary to determine if we need to check
+ * any overlap with reserved device memory.
+ */
+#define LIBXL_RDM_MEM_BOUNDARY_MEMKB_DEFAULT (2048 * 1024)
+
 #define LIBXL_MS_VM_GENID_LEN 16
 typedef struct {
 uint8_t bytes[LIBXL_MS_VM_GENID_LEN];
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 7a0c57d..38a8c3a 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -109,6 +109,10 @@ void libxl__rdm_setdefault(libxl__gc *gc, 
libxl_domain_build_info *b_info)
 {
 if (b_info->u.hvm.rdm.reserve == LIBXL_RDM_RESERVE_FLAG_INVALID)
 b_info->u.hvm.rdm.reserve = LIBXL_RDM_RESERVE_FLAG_RELAXED;
+
+if (b_info->u.hvm.rdm_mem_boundary_memkb == LIBXL_MEMKB_DEFAULT)
+b_info->u.hvm.rdm_mem_boundary_memkb =
+LIBXL_RDM_MEM_BOUNDARY_MEMKB_DEFAULT;
 }
 
 int libxl__domain_build_info_setdefault(libxl__gc *gc,
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index f3c39a0..62ef120 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -922,12 +922,6 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
 int ret, rc = ERROR_FAIL;
 uint64_t mmio_start, lowmem_end, highmem_end;
 libxl_domain_build_info *const info = &d_config->b_info;
-/*
- * Currently we fix this as 2G to guarantte how to handle
- * our rdm policy. But we'll provide a parameter to set
- * this dynamically.
- */
-uint64_t rdm_mem_boundary = 0x8000;
 
 memset(&args, 0, sizeof(struct xc_hvm_build_args));
 /* The params from the configuration file are in Mb, which are then
@@ -966,7 +960,7 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
 args.mmio_start = mmio_start;
 
 ret = libxl__domain_device_construct_rdm(gc, d_config,
- rdm_mem_boundary,
+ 
info->u.hvm.rdm_mem_boundary_memkb*1024,
  &args);
 if (ret) {
 LOG(ERROR, "checking reserved device memory failed");
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 1a8a180..a1b95db 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -484,6 +484,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
("ms_vm_genid",  libxl_ms_vm_genid),
("serial_list",  libxl_string_list),
("rdm", libxl_rdm_reserve),
+   ("rdm_mem_boundary_memkb", MemKB),