Re: [RFC, PATCHv1 24/28] x86/mm: add sync_global_pgds() for configuration with 5-level paging
On Thu, Dec 08, 2016 at 10:42:19AM -0800, Andy Lutomirski wrote:
> On Thu, Dec 8, 2016 at 8:21 AM, Kirill A. Shutemov
> wrote:
> > This basically restores slightly modified version of original
> > sync_global_pgds() which we had before foldedl p4d was introduced.
> >
> > The only modification is protection against 'address' overflow.
> >
> > Signed-off-by: Kirill A. Shutemov
> > ---
> > arch/x86/mm/init_64.c | 47 +++
> > 1 file changed, 47 insertions(+)
> >
> > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> > index a991f5c4c2c4..d637893ac8c2 100644
> > --- a/arch/x86/mm/init_64.c
> > +++ b/arch/x86/mm/init_64.c
> > @@ -92,6 +92,52 @@ __setup("noexec32=", nonx32_setup);
> > * When memory was added/removed make sure all the processes MM have
> > * suitable PGD entries in the local PGD level page.
> > */
> > +#ifdef CONFIG_X86_5LEVEL
> > +void sync_global_pgds(unsigned long start, unsigned long end, int removed)
> > +{
> > +unsigned long address;
> > +
> > + for (address = start; address <= end && address >= start;
> > + address += PGDIR_SIZE) {
> > +const pgd_t *pgd_ref = pgd_offset_k(address);
> > +struct page *page;
> > +
> > +/*
> > + * When it is called after memory hot remove, pgd_none()
> > + * returns true. In this case (removed == 1), we must clear
> > + * the PGD entries in the local PGD level page.
> > + */
> > +if (pgd_none(*pgd_ref) && !removed)
> > +continue;
>
> This isn't quite specific to your patch, but can we assert that, if
> removed=1, then we're not operating on the vmalloc range? Because if
> we do, this will be racy is nasty ways.
Looks like there's no users of removed=1. The last user is gone with
af2cf278ef4f ("x86/mm/hotplug: Don't remove PGD entries in
remove_pagetable()")
I'll just drop it (with separate patch).
--
Kirill A. Shutemov
Re: [RFC, PATCHv1 24/28] x86/mm: add sync_global_pgds() for configuration with 5-level paging
On Thu, Dec 8, 2016 at 8:21 AM, Kirill A. Shutemov
wrote:
> This basically restores slightly modified version of original
> sync_global_pgds() which we had before foldedl p4d was introduced.
>
> The only modification is protection against 'address' overflow.
>
> Signed-off-by: Kirill A. Shutemov
> ---
> arch/x86/mm/init_64.c | 47 +++
> 1 file changed, 47 insertions(+)
>
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index a991f5c4c2c4..d637893ac8c2 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -92,6 +92,52 @@ __setup("noexec32=", nonx32_setup);
> * When memory was added/removed make sure all the processes MM have
> * suitable PGD entries in the local PGD level page.
> */
> +#ifdef CONFIG_X86_5LEVEL
> +void sync_global_pgds(unsigned long start, unsigned long end, int removed)
> +{
> +unsigned long address;
> +
> + for (address = start; address <= end && address >= start;
> + address += PGDIR_SIZE) {
> +const pgd_t *pgd_ref = pgd_offset_k(address);
> +struct page *page;
> +
> +/*
> + * When it is called after memory hot remove, pgd_none()
> + * returns true. In this case (removed == 1), we must clear
> + * the PGD entries in the local PGD level page.
> + */
> +if (pgd_none(*pgd_ref) && !removed)
> +continue;
This isn't quite specific to your patch, but can we assert that, if
removed=1, then we're not operating on the vmalloc range? Because if
we do, this will be racy is nasty ways.
[RFC, PATCHv1 24/28] x86/mm: add sync_global_pgds() for configuration with 5-level paging
This basically restores slightly modified version of original
sync_global_pgds() which we had before foldedl p4d was introduced.
The only modification is protection against 'address' overflow.
Signed-off-by: Kirill A. Shutemov
---
arch/x86/mm/init_64.c | 47 +++
1 file changed, 47 insertions(+)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index a991f5c4c2c4..d637893ac8c2 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -92,6 +92,52 @@ __setup("noexec32=", nonx32_setup);
* When memory was added/removed make sure all the processes MM have
* suitable PGD entries in the local PGD level page.
*/
+#ifdef CONFIG_X86_5LEVEL
+void sync_global_pgds(unsigned long start, unsigned long end, int removed)
+{
+unsigned long address;
+
+ for (address = start; address <= end && address >= start;
+ address += PGDIR_SIZE) {
+const pgd_t *pgd_ref = pgd_offset_k(address);
+struct page *page;
+
+/*
+ * When it is called after memory hot remove, pgd_none()
+ * returns true. In this case (removed == 1), we must clear
+ * the PGD entries in the local PGD level page.
+ */
+if (pgd_none(*pgd_ref) && !removed)
+continue;
+
+spin_lock(&pgd_lock);
+list_for_each_entry(page, &pgd_list, lru) {
+pgd_t *pgd;
+spinlock_t *pgt_lock;
+
+pgd = (pgd_t *)page_address(page) + pgd_index(address);
+/* the pgt_lock only for Xen */
+pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
+spin_lock(pgt_lock);
+
+if (!pgd_none(*pgd_ref) && !pgd_none(*pgd))
+BUG_ON(pgd_page_vaddr(*pgd)
+ != pgd_page_vaddr(*pgd_ref));
+
+if (removed) {
+if (pgd_none(*pgd_ref) && !pgd_none(*pgd))
+pgd_clear(pgd);
+} else {
+if (pgd_none(*pgd))
+set_pgd(pgd, *pgd_ref);
+}
+
+spin_unlock(pgt_lock);
+}
+spin_unlock(&pgd_lock);
+}
+}
+#else
void sync_global_pgds(unsigned long start, unsigned long end, int removed)
{
unsigned long address;
@@ -145,6 +191,7 @@ void sync_global_pgds(unsigned long start, unsigned long
end, int removed)
spin_unlock(&pgd_lock);
}
}
+#endif
/*
* NOTE: This function is marked __ref because it calls __init function
--
2.10.2
