[V4,04/10] xen: introduce mark_page_free

Commit Message

Penny Zheng July 28, 2021, 10:27 a.m. UTC

This commit defines a new helper mark_page_free to extract common code,
like following the same cache/TLB coherency policy, between free_heap_pages
and the new function free_staticmem_pages, which will be introduced later.

Signed-off-by: Penny Zheng <[e-mail]>
Acked-by: Jan Beulich <[e-mail]>
---
 xen/common/page_alloc.c | 89 ++++++++++++++++++++++-------------------
 1 file changed, 48 insertions(+), 41 deletions(-)

Comments

Julien Grall Aug. 11, 2021, 2:08 p.m. UTC | #1

Hi Penny,

On 28/07/2021 11:27, Penny Zheng wrote:
> This commit defines a new helper mark_page_free to extract common code,
> like following the same cache/TLB coherency policy, between free_heap_pages
> and the new function free_staticmem_pages, which will be introduced later.
> 
> Signed-off-by: Penny Zheng <[e-mail]>
> Acked-by: Jan Beulich <[e-mail]>
> ---
>   xen/common/page_alloc.c | 89 ++++++++++++++++++++++-------------------
>   1 file changed, 48 insertions(+), 41 deletions(-)
> 
> diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
> index 958ba0cd92..a3ee5eca9e 100644
> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -1376,6 +1376,53 @@ bool scrub_free_pages(void)
>       return node_to_scrub(false) != NUMA_NO_NODE;
>   }
>   
> +static void mark_page_free(struct page_info *pg, mfn_t mfn)
> +{
> +    ASSERT(mfn_x(mfn) == mfn_x(page_to_mfn(pg)));

NIT: If I got it correctly, the assumption is page_to_mfn() is 
expensive, so we want to avoid the conversation. I am not sure I agree 
with that but I would at least suggest to write it down in the commit 
message.

So it is easier for the next person to figure out the rationale. 
Something like:

"The PDX compression makes makes conversion between the MFN and the page 
can be potentially non-trivial. As the function is internal, pass the 
MFN and the page. They are both expected to match."

For the rest of the patch:

Reviewed-by: Julien Grall <[e-mail]>

Cheers,

Patch

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 958ba0cd92..a3ee5eca9e 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -1376,6 +1376,53 @@  bool scrub_free_pages(void)
     return node_to_scrub(false) != NUMA_NO_NODE;
 }
 
+static void mark_page_free(struct page_info *pg, mfn_t mfn)
+{
+    ASSERT(mfn_x(mfn) == mfn_x(page_to_mfn(pg)));
+
+    /*
+     * Cannot assume that count_info == 0, as there are some corner cases
+     * where it isn't the case and yet it isn't a bug:
+     *  1. page_get_owner() is NULL
+     *  2. page_get_owner() is a domain that was never accessible by
+     *     its domid (e.g., failed to fully construct the domain).
+     *  3. page was never addressable by the guest (e.g., it's an
+     *     auto-translate-physmap guest and the page was never included
+     *     in its pseudophysical address space).
+     * In all the above cases there can be no guest mappings of this page.
+     */
+    switch ( pg->count_info & PGC_state )
+    {
+    case PGC_state_inuse:
+        BUG_ON(pg->count_info & PGC_broken);
+        pg->count_info = PGC_state_free;
+        break;
+
+    case PGC_state_offlining:
+        pg->count_info = (pg->count_info & PGC_broken) |
+                         PGC_state_offlined;
+        tainted = 1;
+        break;
+
+    default:
+        printk(XENLOG_ERR
+               "pg MFN %"PRI_mfn" c=%#lx o=%u v=%#lx t=%#x\n",
+               mfn_x(mfn),
+               pg->count_info, pg->v.free.order,
+               pg->u.free.val, pg->tlbflush_timestamp);
+        BUG();
+    }
+
+    /* If a page has no owner it will need no safety TLB flush. */
+    pg->u.free.need_tlbflush = (page_get_owner(pg) != NULL);
+    if ( pg->u.free.need_tlbflush )
+        page_set_tlbflush_timestamp(pg);
+
+    /* This page is not a guest frame any more. */
+    page_set_owner(pg, NULL); /* set_gpfn_from_mfn snoops pg owner */
+    set_gpfn_from_mfn(mfn_x(mfn), INVALID_M2P_ENTRY);
+}
+
 /* Free 2^@order set of pages. */
 static void free_heap_pages(
     struct page_info *pg, unsigned int order, bool need_scrub)
@@ -1392,47 +1439,7 @@  static void free_heap_pages(
 
     for ( i = 0; i < (1 << order); i++ )
     {
-        /*
-         * Cannot assume that count_info == 0, as there are some corner cases
-         * where it isn't the case and yet it isn't a bug:
-         *  1. page_get_owner() is NULL
-         *  2. page_get_owner() is a domain that was never accessible by
-         *     its domid (e.g., failed to fully construct the domain).
-         *  3. page was never addressable by the guest (e.g., it's an
-         *     auto-translate-physmap guest and the page was never included
-         *     in its pseudophysical address space).
-         * In all the above cases there can be no guest mappings of this page.
-         */
-        switch ( pg[i].count_info & PGC_state )
-        {
-        case PGC_state_inuse:
-            BUG_ON(pg[i].count_info & PGC_broken);
-            pg[i].count_info = PGC_state_free;
-            break;
-
-        case PGC_state_offlining:
-            pg[i].count_info = (pg[i].count_info & PGC_broken) |
-                               PGC_state_offlined;
-            tainted = 1;
-            break;
-
-        default:
-            printk(XENLOG_ERR
-                   "pg[%u] MFN %"PRI_mfn" c=%#lx o=%u v=%#lx t=%#x\n",
-                   i, mfn_x(mfn) + i,
-                   pg[i].count_info, pg[i].v.free.order,
-                   pg[i].u.free.val, pg[i].tlbflush_timestamp);
-            BUG();
-        }
-
-        /* If a page has no owner it will need no safety TLB flush. */
-        pg[i].u.free.need_tlbflush = (page_get_owner(&pg[i]) != NULL);
-        if ( pg[i].u.free.need_tlbflush )
-            page_set_tlbflush_timestamp(&pg[i]);
-
-        /* This page is not a guest frame any more. */
-        page_set_owner(&pg[i], NULL); /* set_gpfn_from_mfn snoops pg owner */
-        set_gpfn_from_mfn(mfn_x(mfn) + i, INVALID_M2P_ENTRY);
+        mark_page_free(&pg[i], mfn_add(mfn, i));
 
         if ( need_scrub )
         {