On Mon, May 11, 2020 at 09:43:30AM -0700, Dave Hansen wrote:
> On 5/11/20 9:37 AM, Kirill A. Shutemov wrote:
> > - memblock_add(entry->addr, entry->size);
> > + if (entry->addr >= MAXMEM || end >= MAXMEM)
> > + pr_err_once("Some physical memory is not addressable in the paging mode.\n");
>
> Hi Kirill,
>
> Thanks for fixing this!
>
> Could we make the pr_err() a bit more informative, though? It would be
> nice to print out how much memory (or which addresses at least) are
> being thrown away.
>
> I was also thinking that it would be handy to tell folks how to rectify
> the situation. Should we perhaps dump out the runtime status of
> X86_FEATURE_LA57?
Something like this (incremental patch)?
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 022fe1de8940..172b4244069f 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1280,8 +1280,8 @@ void __init e820__memory_setup(void)
void __init e820__memblock_setup(void)
{
+ u64 size, end, not_addressable = 0;
int i;
- u64 end;
/*
* The bootstrap memblock region count maximum is 128 entries
@@ -1307,16 +1307,24 @@ void __init e820__memblock_setup(void)
if (entry->type != E820_TYPE_RAM && entry->type != E820_TYPE_RESERVED_KERN)
continue;
- if (entry->addr >= MAXMEM || end >= MAXMEM)
- pr_err_once("Some physical memory is not addressable in the paging mode.\n");
-
- if (entry->addr >= MAXMEM)
+ if (entry->addr >= MAXMEM) {
+ not_addressable += entry->size;
continue;
+ }
end = min_t(u64, end, MAXMEM - 1);
+ size = end - entry->addr;
+ not_addressable += entry->size - size;
memblock_add(entry->addr, end - entry->addr);
}
+ if (not_addressable) {
+ pr_err("%lldMB of physical memory is not addressable in the paging mode\n",
+ not_addressable >> 20);
+ if (!pgtable_l5_enabled())
+ pr_err("Consider enabling 5-level paging\n");
+ }
+
/* Throw away partial pages: */
memblock_trim_memory(PAGE_SIZE);
--
Kirill A. Shutemov
