Re: [PATCHv7 02/14] mm: Add support for unaccepted memory

Mike Rapoport
2022-09-24T09:36:38Z

On Sat, Sep 24, 2022 at 04:03:02AM +0300, Kirill A. Shutemov wrote:
> On Thu, Sep 22, 2022 at 09:31:12AM -0500, Tom Lendacky wrote:
> > On 9/8/22 14:28, Mike Rapoport wrote:
> > > On Thu, Sep 08, 2022 at 09:23:07AM -0700, Dionna Amalie Glaze wrote:
> > > > >
> > > > > Looks like the first access to the memory map fails, although I think
> > > > > it's not in INIT_LIST_HEAD() but rather in init_page_count().
> > > > >
> > > > > I'd start with making sure that page_alloc::memmap_alloc() actually returns
> > > > > accepted memory. If you build kernel with CONFIG_DEBUG_VM=y the memory map
> > > > > will poisoned in this function, so my guess is it'd crash there.
> > > > >
> > > >
> > > > That's a wonderful hint, thank you! I did not run this test
> > > > CONFIG_DEBUG_VM set, but you think it's possible it could still be
> > > > here?
> > >
> > > It depends on how you configured your kernel. Say, defconfig does not set
> > > it.
> > >
> >
> > I also hit the issue at 256GB. My config is using CONFIG_SPARSEMEM_VMEMMAP
> > and fails in memmap_init_range() when attempting to add the first PFN. It
> > looks like the underlying page that is backing the vmemmap has not been
> > accepted (I receive a #VC 0x404 => page not validated).
> >
> > Kirill, is this a path that you've looked at? It would appear that somewhere
> > in the vmemmap_populate_hugepages() path, some memory acceptance needs to be
> > done for the pages that are used to back vmemmap. I'm not very familiar with
> > this code, so I'm not sure why everything works for a guest with 255GB of
> > memory, but then fails for a guest with 256GB of memory.
>
> Hm. I don't have machine that large at hands at the moment. And I have not
> looked at the codepath before.
>
> I will try to look into the issue.

I'd add some printks to verify we actually try to accept the allocated
memory. E.g. something like the patch below:

diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
index 9ec2304272dc..8f00639facc4 100644
--- a/arch/x86/mm/unaccepted_memory.c
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -22,6 +22,9 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
if (!boot_params.unaccepted_memory)
return;

+ if (system_state == SYSTEM_BOOTING)
+ pr_info("%s: start: %pa end: %pa %pS\n", __func__, &start, &end, (void *)_RET_IP_);
+
bitmap = __va(boot_params.unaccepted_memory);
range_start = start / PMD_SIZE;

diff --git a/mm/memblock.c b/mm/memblock.c
index a1f7f8b304d5..029dd520102d 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1535,7 +1535,7 @@ void * __init memblock_alloc_exact_nid_raw(
phys_addr_t min_addr, phys_addr_t max_addr,
int nid)
{
- memblock_dbg("%s: %llu bytes align=0x%llx nid=%d from=%pa max_addr=%pa %pS\n",
+ pr_info("%s: %llu bytes align=0x%llx nid=%d from=%pa max_addr=%pa %pS\n",
__func__, (u64)size, (u64)align, nid, &min_addr,
&max_addr, (void *)_RET_IP_);

@@ -1567,7 +1567,7 @@ void * __init memblock_alloc_try_nid_raw(
phys_addr_t min_addr, phys_addr_t max_addr,
int nid)
{
- memblock_dbg("%s: %llu bytes align=0x%llx nid=%d from=%pa max_addr=%pa %pS\n",
+ pr_info("%s: %llu bytes align=0x%llx nid=%d from=%pa max_addr=%pa %pS\n",
__func__, (u64)size, (u64)align, nid, &min_addr,
&max_addr, (void *)_RET_IP_);

> --
> Kiryl Shutsemau / Kirill A. Shutemov
>

--
Sincerely yours,
Mike.