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Re: [PATCH V4 08/10] xen/arm: introduce acquire_staticmem_pages and acquire_domstatic_pages
Hi Penny,
On 28/07/2021 11:27, Penny Zheng wrote:
alloc_staticmem_pages aims to acquire nr_mfns contiguous pages of
static memory. And it is the equivalent of alloc_heap_pages for static
memory. Here only covers acquiring pre-configured static memory.
For each page, it shall check if the page is reserved(PGC_reserved)
and free. It shall also do a set of necessary initialization, which are
mostly the same ones in alloc_heap_pages, like, following the same
cache-coherency policy and turning page status into PGC_state_inuse, etc.
acquire_domstatic_pages is the equivalent of alloc_domheap_pages for
static memory, and it is to acquire nr_mfns contiguous pages of static memory
and assign them to one specific domain.
It uses acquire_staticmem_pages to acquire nr_mfns pre-configured pages of
static memory, then on success, it will use assign_pages to assign those pages
to one specific domain.
Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
---
v4 change:
- moving tlb/cache flush outside of the locked region, considering XSA-364
and reducing the amount of work happening with the heap_lock held
- remove MEMF_no_refcount case
- make acquire_staticmem_pages/acquire_domstatic_pages being __init
---
xen/common/page_alloc.c | 108 +++++++++++++++++++++++++++++++++++++++-
xen/include/xen/mm.h | 3 ++
2 files changed, 109 insertions(+), 2 deletions(-)
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index e279c6f713..b0edaf12b3 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -151,6 +151,10 @@
#define p2m_pod_offline_or_broken_replace(pg) BUG_ON(pg != NULL)
#endif
+#ifndef CONFIG_STATIC_MEMORY
+#define PGC_reserved 0
+#endif
+
/*
* Comma-separated list of hexadecimal page numbers containing bad bytes.
* e.g. 'badpage=0x3f45,0x8a321'.
@@ -1065,6 +1069,73 @@ static struct page_info *alloc_heap_pages(
return pg;
}
+#ifdef CONFIG_STATIC_MEMORY
Rather than having multiple #ifdef in the code. Could we bundle all the
functions for static allocation in a single place?
+/*
+ * Acquire nr_mfns contiguous reserved pages, starting at #smfn, of
+ * static memory.
+ */
+static struct page_info * __init acquire_staticmem_pages(unsigned long nr_mfns,
+ mfn_t smfn,
+ unsigned int memflags)
NIT: I find more intuitive if we pass the start MFN first and then the
number of pages. So this can be seen as a range.
If you agree with that, then the caller would also have to be changed.
+{
+ bool need_tlbflush = false;
+ uint32_t tlbflush_timestamp = 0;
+ unsigned long i;
+ struct page_info *pg;
+
+ /* For now, it only supports pre-configured static memory. */
This comment doesn't seem to match the check below.
+ if ( !mfn_valid(smfn) || !nr_mfns )
This check only guarantees that there will be a page for the first MFN.
Shouldn't we also check for the other MFNs?
+ return NULL;
+
+ spin_lock(&heap_lock);
+
+ pg = mfn_to_page(smfn);
+
+ for ( i = 0; i < nr_mfns; i++ )
+ {
+ /*
+ * Reference count must continuously be zero for free pages
+ * of static memory(PGC_reserved).
+ */
How about: "The page should be reserved and not yet allocated"?
+ if ( pg[i].count_info != (PGC_state_free | PGC_reserved) )
+ {
+ printk(XENLOG_ERR
+ "pg[%lu] Static MFN %"PRI_mfn" c=%#lx t=%#x\n",
+ i, mfn_x(page_to_mfn(pg + i)),
+ pg[i].count_info, pg[i].tlbflush_timestamp);
+ BUG();
This BUG() can be easily hit by misconfiguring the Device-Tree. I think
it would be best if we return an error and revert the changes.
+ }
+
+ if ( !(memflags & MEMF_no_tlbflush) )
+ accumulate_tlbflush(&need_tlbflush, &pg[i],
+ &tlbflush_timestamp);
+
+ /*
+ * Preserve flag PGC_reserved and change page state
+ * to PGC_state_inuse.
+ */
+ pg[i].count_info = (PGC_reserved | PGC_state_inuse);
+ /* Initialise fields which have other uses for free pages. */
+ pg[i].u.inuse.type_info = 0;
+ page_set_owner(&pg[i], NULL);
+ }
+
+ spin_unlock(&heap_lock);
+
+ if ( need_tlbflush )
+ filtered_flush_tlb_mask(tlbflush_timestamp);
+
+ /*
+ * Ensure cache and RAM are consistent for platforms where the guest
+ * can control its own visibility of/through the cache.
+ */
+ for ( i = 0; i < nr_mfns; i++ )
+ flush_page_to_ram(mfn_x(smfn) + i, !(memflags & MEMF_no_icache_flush));
+
+ return pg;
+}
+#endif
+
/* Remove any offlined page in the buddy pointed to by head. */
static int reserve_offlined_page(struct page_info *head)
{
@@ -2306,7 +2377,7 @@ int assign_pages(
for ( i = 0; i < nr; i++ )
{
- ASSERT(!(pg[i].count_info & ~PGC_extra));
+ ASSERT(!(pg[i].count_info & ~(PGC_extra | PGC_reserved)));
if ( pg[i].count_info & PGC_extra )
extra_pages++;
}
@@ -2345,7 +2416,8 @@ int assign_pages(
page_set_owner(&pg[i], d);
smp_wmb(); /* Domain pointer must be visible before updating refcnt.
*/
pg[i].count_info =
- (pg[i].count_info & PGC_extra) | PGC_allocated | 1;
+ (pg[i].count_info & (PGC_extra | PGC_reserved)) | PGC_allocated |
1;
+
page_list_add_tail(&pg[i], page_to_list(d, &pg[i]));
}
@@ -2411,6 +2483,38 @@ struct page_info *alloc_domheap_pages(
return pg;
}
+#ifdef CONFIG_STATIC_MEMORY
+/*
+ * Acquire nr_mfns contiguous pages, starting at #smfn, of static memory,
+ * then assign them to one specific domain #d.
+ */
+struct page_info * __init acquire_domstatic_pages(struct domain *d,
+ unsigned long nr_mfns,
+ mfn_t smfn, unsigned int
memflags)
+{
+ struct page_info *pg = NULL;
+
+ ASSERT(!in_irq());
+
+ pg = acquire_staticmem_pages(nr_mfns, smfn, memflags);
+ if ( !pg )
+ return NULL;
+
+ /*
+ * MEMF_no_owner/MEMF_no_refcount cases are missing here because
+ * right now, acquired static memory is only for guest RAM.
+ */
+ ASSERT(d);
+ if ( assign_pages(pg, nr_mfns, d, memflags) )
+ {
+ free_staticmem_pages(pg, nr_mfns, memflags & MEMF_no_scrub);
+ return NULL;
+ }
+
+ return pg;
+}
+#endif
+
void free_domheap_pages(struct page_info *pg, unsigned int order)
{
struct domain *d = page_get_owner(pg);
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 2e75cdcbb7..62e8e2ad61 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -89,6 +89,9 @@ bool scrub_free_pages(void);
/* These functions are for static memory */
void free_staticmem_pages(struct page_info *pg, unsigned long nr_mfns,
bool need_scrub);
+struct page_info *acquire_domstatic_pages(struct domain *d,
+ unsigned long nr_mfns, mfn_t smfn,
+ unsigned int memflags);
#endif
/* Map machine page range in Xen virtual address space. */
Cheers,
--
Julien Grall
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