Hi Jan,
On 3/12/2024 1:07 AM, Jan Beulich wrote:
I'm afraid the title doesn't really say what the patch actually means
to achieve.
On 08.03.2024 02:54, Henry Wang wrote:
Previous commits enable the toolstack to get the domain memory map,
therefore instead of hardcoding the guest magic pages region, use
the XEN_DOMCTL_get_mem_map domctl to get the start address of the
guest magic pages region. Add the (XEN)MEMF_force_heap_alloc memory
flags to force populate_physmap() to allocate page from domheap
instead of using 1:1 or static allocated pages to map the magic pages.
A patch description wants to be (largely) self-contained. "Previous
commits" shouldn't be mentioned; recall that the sequence in which
patches go in is unknown to you up front. (In fact the terms "commit"
or "patch" should be avoided altogether when describing what a patch
does. The only valid use I can think of is when referring to commits
already in the tree, and then typically by quoting their hash and
title.)
Thanks for the detailed explanation. I will rewrite the title and part
of the commit message in v3 to make it clear.
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -41,6 +41,11 @@
#define XENMEMF_exact_node(n) (XENMEMF_node(n) | XENMEMF_exact_node_request)
/* Flag to indicate the node specified is virtual node */
#define XENMEMF_vnode (1<<18)
+/*
+ * Flag to force populate physmap to use pages from domheap instead of 1:1
+ * or static allocation.
+ */
+#define XENMEMF_force_heap_alloc (1<<19)
#endif
If this is for populate_physmap only, then other sub-ops need to reject
its use.
I have to admit I'm a little wary of allocating another flag here and ...
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -205,6 +205,8 @@ struct npfec {
#define MEMF_no_icache_flush (1U<<_MEMF_no_icache_flush)
#define _MEMF_no_scrub 8
#define MEMF_no_scrub (1U<<_MEMF_no_scrub)
+#define _MEMF_force_heap_alloc 9
+#define MEMF_force_heap_alloc (1U<<_MEMF_force_heap_alloc)
#define _MEMF_node 16
#define MEMF_node_mask ((1U << (8 * sizeof(nodeid_t))) - 1)
#define MEMF_node(n) ((((n) + 1) & MEMF_node_mask) << _MEMF_node)
... here - we don't have that many left. Since other sub-ops aren't
intended to support this flag, did you consider adding another (perhaps
even arch-specific) sub-op instead?
Not really, I basically followed the discussion from [1] to implement
this patch. However I understand your concern. Just want to make sure if
I understand your suggestion correctly, by "adding another sub-op" you
mean adding a sub-op similar as "XENMEM_populate_physmap" but only with
executing the "else" part I want, so we can drop the use of these two
added flags? Thanks!
[1]
https://lore.kernel.org/xen-devel/3982ba47-6709-47e3-a9c2-e2d3b4a2d...@xen.org/
Kind regards,
Henry
Jan
