Re: [PATCH 2/4] mm: introduce mm_forbids_zeropage function
Reviewed-by: Paolo Bonzini pbonz...@redhat.com
On 10/22/2014 01:09 PM, Dominik Dingel wrote:
Add a new function stub to allow architectures to disable for
an mm_structthe backing of non-present, anonymous pages with
read-only empty zero pages.
Signed-off-by: Dominik Dingel din...@linux.vnet.ibm.com
---
include/linux/mm.h | 4
mm/huge_memory.c | 2 +-
mm/memory.c| 2 +-
3 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index cd33ae2..0a2022e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -56,6 +56,10 @@ extern int sysctl_legacy_va_layout;
#define __pa_symbol(x) __pa(RELOC_HIDE((unsigned long)(x), 0))
#endif
+#ifndef mm_forbids_zeropage
+#define mm_forbids_zeropage(X) (0)
+#endif
+
extern unsigned long sysctl_user_reserve_kbytes;
extern unsigned long sysctl_admin_reserve_kbytes;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index de98415..357a381 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -805,7 +805,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm,
struct vm_area_struct *vma,
return VM_FAULT_OOM;
if (unlikely(khugepaged_enter(vma, vma-vm_flags)))
return VM_FAULT_OOM;
- if (!(flags FAULT_FLAG_WRITE)
+ if (!(flags FAULT_FLAG_WRITE) !mm_forbids_zeropage(mm)
transparent_hugepage_use_zero_page()) {
spinlock_t *ptl;
pgtable_t pgtable;
diff --git a/mm/memory.c b/mm/memory.c
index 64f82aa..f275a9d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2640,7 +2640,7 @@ static int do_anonymous_page(struct mm_struct *mm,
struct vm_area_struct *vma,
return VM_FAULT_SIGBUS;
/* Use the zero-page for reads */
- if (!(flags FAULT_FLAG_WRITE)) {
+ if (!(flags FAULT_FLAG_WRITE) !mm_forbids_zeropage(mm)) {
entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
vma-vm_page_prot));
page_table = pte_offset_map_lock(mm, pmd, address, ptl);
--
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Re: [PATCH 2/4] mm: introduce mm_forbids_zeropage function
On Wed, 22 Oct 2014 13:09:28 +0200 Dominik Dingel din...@linux.vnet.ibm.com wrote: Add a new function stub to allow architectures to disable for an mm_structthe backing of non-present, anonymous pages with read-only empty zero pages. ... --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -56,6 +56,10 @@ extern int sysctl_legacy_va_layout; #define __pa_symbol(x) __pa(RELOC_HIDE((unsigned long)(x), 0)) #endif +#ifndef mm_forbids_zeropage +#define mm_forbids_zeropage(X) (0) +#endif Can we document this please? What it does, why it does it. We should also specify precisely which arch header file is responsible for defining mm_forbids_zeropage. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 2/4] mm: introduce mm_forbids_zeropage function
On Wed, 22 Oct 2014 12:22:23 -0700 Andrew Morton a...@linux-foundation.org wrote: On Wed, 22 Oct 2014 13:09:28 +0200 Dominik Dingel din...@linux.vnet.ibm.com wrote: Add a new function stub to allow architectures to disable for an mm_structthe backing of non-present, anonymous pages with read-only empty zero pages. ... --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -56,6 +56,10 @@ extern int sysctl_legacy_va_layout; #define __pa_symbol(x) __pa(RELOC_HIDE((unsigned long)(x), 0)) #endif +#ifndef mm_forbids_zeropage +#define mm_forbids_zeropage(X) (0) +#endif Can we document this please? What it does, why it does it. We should also specify precisely which arch header file is responsible for defining mm_forbids_zeropage. I will add a comment like: /* * To prevent common memory management code establishing * a zero page mapping on a read fault. * This function should be implemented within asm/pgtable.h. * s390 does this to prevent multiplexing of hardware bits * related to the physical page in case of virtualization. */ Okay? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majord...@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: a href=mailto:d...@kvack.org; em...@kvack.org /a -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 2/4] mm: introduce mm_forbids_zeropage function
On Wed, 22 Oct 2014 21:45:52 +0200 Dominik Dingel din...@linux.vnet.ibm.com wrote: +#ifndef mm_forbids_zeropage +#define mm_forbids_zeropage(X) (0) +#endif Can we document this please? What it does, why it does it. We should also specify precisely which arch header file is responsible for defining mm_forbids_zeropage. I will add a comment like: /* * To prevent common memory management code establishing * a zero page mapping on a read fault. * This function should be implemented within asm/pgtable.h. s/function should be implemented/macro should be defined/ * s390 does this to prevent multiplexing of hardware bits * related to the physical page in case of virtualization. */ Okay? Looks great, thanks. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
