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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] preparing for 4.5.1
On Mon, 2015-04-13 at 09:35 +0100, Jan Beulich wrote:
> >>> On 02.04.15 at 12:01, <ian.campbell@xxxxxxxxxx> wrote:
> > On Thu, 2015-03-26 at 17:07 +0000, Jan Beulich wrote:
> >> having been released mid January, it is time to get ready for 4.5.1-rc1.
> >> Please reply with backport requests which you consider necessary but
> >> still missing. Please also be patient with them being pulled in - I'll be
> >> gone the coming two weeks, and I'd hope to get an RC1 put together
> >> soon thereafter.
> >
> > On my list for ARM I have this patch, which also touches x86. What do
> > you think?
>
> If it fixes a real problem in 4.5 (rather than just a theoretical one,
> exposed only in 4.6), then I'm fine with this (and assume since it's
> mostly for ARM you'll take care of doing and applying the backport).
The original impetus was a bit lost in the various iterations. I think
it was something which was exposed by Vijay's new ITS code, which did a
larger vmalloc than any existing code and exposed the issue. Vijay, is
that correct?
I think it is unlikely that there is anything in 4.5 which would do a
similarly large vmalloc, or at least I don't recall any reports of such.
So I think the conclusion is not to backport the patch, unless someone
knows of a practical issue on 4.5.
For those new to the CC line the commit is below.
Thanks,
Ian.
commit c2453291b177cc2e89dc104bd4233c3d8bb73922
Author: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
Date: Tue Mar 24 17:14:47 2015 +0530
xen: Add populate_pt_range interface to reserve non-leaf level table entries
On x86, for the pages mapped with PAGE_HYPERVISOR attribute
non-leaf page tables are allocated with valid pte entries.
and with MAP_SMALL_PAGES attribute only non-leaf page tables are
allocated with invalid (valid bit set to 0) pte entries.
However on arm this is not the case. On arm for the pages
mapped with PAGE_HYPERVISOR and MAP_SMALL_PAGES both
non-leaf and leaf level page table are allocated with valid bit
in pte entries.
This behaviour in arm makes common vmap code fail to
allocate memory beyond 128MB as described below.
In vm_init, map_pages_to_xen() is called for mapping
vm_bitmap. Initially one page of vm_bitmap is allocated
and mapped using PAGE_HYPERVISOR attribute.
For the rest of vm_bitmap pages, MAP_SMALL_PAGES attribute
is used to map.
In ARM for both PAGE_HYPERVISOR and MAP_SMALL_PAGES, valid bit
is set to 1 in pte entry for these mapping.
In vm_alloc(), map_pages_to_xen() is failing for >128MB because
for this next vm_bitmap page the mapping is already set in vm_init()
with valid bit set in pte entry. So map_pages_to_xen() in
ARM returns error.
With this patch, MAP_SMALL_PAGES is dropped and arch specific
populate_pt_range() api is introduced to populate non-leaf
page table entries for the requested pages. Added RESERVE option
to map non-leaf page table entries.
Signed-off-by: Vijaya Kumar K<Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
[ ijc -- rewrote subject line ]
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 7d4ba0c..d103f8f 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -827,7 +827,8 @@ static int create_xen_table(lpae_t *entry)
enum xenmap_operation {
INSERT,
- REMOVE
+ REMOVE,
+ RESERVE
};
static int create_xen_entries(enum xenmap_operation op,
@@ -859,12 +860,15 @@ static int create_xen_entries(enum xenmap_operation op,
switch ( op ) {
case INSERT:
+ case RESERVE:
if ( third[third_table_offset(addr)].pt.valid )
{
printk("create_xen_entries: trying to replace an existing
mapping addr=%lx mfn=%lx\n",
addr, mfn);
return -EINVAL;
}
+ if ( op == RESERVE )
+ break;
pte = mfn_to_xen_entry(mfn, ai);
pte.pt.table = 1;
write_pte(&third[third_table_offset(addr)], pte);
@@ -898,6 +902,13 @@ int map_pages_to_xen(unsigned long virt,
{
return create_xen_entries(INSERT, virt, mfn, nr_mfns, flags);
}
+
+int populate_pt_range(unsigned long virt, unsigned long mfn,
+ unsigned long nr_mfns)
+{
+ return create_xen_entries(RESERVE, virt, mfn, nr_mfns, 0);
+}
+
void destroy_xen_mappings(unsigned long v, unsigned long e)
{
create_xen_entries(REMOVE, v, 0, (e - v) >> PAGE_SHIFT, 0);
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 8e29675..786ed47 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5725,6 +5725,12 @@ int map_pages_to_xen(
return 0;
}
+int populate_pt_range(unsigned long virt, unsigned long mfn,
+ unsigned long nr_mfns)
+{
+ return map_pages_to_xen(virt, mfn, nr_mfns, MAP_SMALL_PAGES);
+}
+
void destroy_xen_mappings(unsigned long s, unsigned long e)
{
bool_t locking = system_state > SYS_STATE_boot;
diff --git a/xen/common/vmap.c b/xen/common/vmap.c
index 783cea3..739d468 100644
--- a/xen/common/vmap.c
+++ b/xen/common/vmap.c
@@ -40,7 +40,7 @@ void __init vm_init(void)
bitmap_fill(vm_bitmap, vm_low);
/* Populate page tables for the bitmap if necessary. */
- map_pages_to_xen(va, 0, vm_low - nr, MAP_SMALL_PAGES);
+ populate_pt_range(va, 0, vm_low - nr);
}
void *vm_alloc(unsigned int nr, unsigned int align)
diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
index 3e7b0ae..8de5e26 100644
--- a/xen/include/asm-arm/page.h
+++ b/xen/include/asm-arm/page.h
@@ -64,7 +64,6 @@
#define PAGE_HYPERVISOR (WRITEALLOC)
#define PAGE_HYPERVISOR_NOCACHE (DEV_SHARED)
#define PAGE_HYPERVISOR_WC (DEV_WC)
-#define MAP_SMALL_PAGES PAGE_HYPERVISOR
/*
* Stage 2 Memory Type.
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index a769084..a066363 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -55,7 +55,12 @@ int map_pages_to_xen(
unsigned long nr_mfns,
unsigned int flags);
void destroy_xen_mappings(unsigned long v, unsigned long e);
-
+/*
+ * Create only non-leaf page table entries for the
+ * page range in Xen virtual address space.
+ */
+int populate_pt_range(unsigned long virt, unsigned long mfn,
+ unsigned long nr_mfns);
/* Claim handling */
unsigned long domain_adjust_tot_pages(struct domain *d, long pages);
int domain_set_outstanding_pages(struct domain *d, unsigned long pages);
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