Attachment 302525 Details for Bug 441543 – Patch to avoid keeping a alias mapping for freed init memory pages

[patch] Patch to avoid keeping a alias mapping for freed init memory pages

0001-Xen-Clear-__START_KERNEL_map-PTEs-on-free_init_page.patch (text/plain), 1.43 KB, created by Eduardo Habkost on 2008-04-15 21:17:28 UTC

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Creator: Eduardo Habkost

Created: 2008-04-15 21:17:28 UTC

Size: 1.43 KB

patch

obsolete

>From 9ee9833fcc88cf1196e959b7f6342897f9df043b Mon Sep 17 00:00:00 2001
>From: Eduardo Habkost <ehabkost@redhat.com>
>Date: Tue, 15 Apr 2008 17:59:31 -0300
>Subject: [PATCH] Xen: Clear __START_KERNEL_map PTEs on free_init_pages() (REVIEWME)
>
>We need to kill the __START_KERNEL_map aliases of the freed init pages
>otherwise we won't be able to pin those pages as pagetables later, because
>there will be a read-write alias even after make_lowpage_readonly().
>
>Probably using set_memory_ro() instead of make_lowpage_readonly()
>when pinning pages will be better.
>
>This should fix the pagetable pinning problems reported at
>https://bugzilla.redhat.com/show_bug.cgi?id=441543
>
>Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>---
> arch/x86/mm/init_64.c |   10 ++++++++++
> 1 files changed, 10 insertions(+), 0 deletions(-)
>
>diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>index 494f141..243bdf3 100644
>--- a/arch/x86/mm/init_64.c
>+++ b/arch/x86/mm/init_64.c
>@@ -1093,6 +1093,16 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
> 			POISON_FREE_INITMEM, PAGE_SIZE);
> 		free_page(addr);
> 		totalram_pages++;
>+		if (begin >= __START_KERNEL_map) {
>+			pte_t *kpte;
>+			unsigned int l;
>+			/* __START_KERNEL_map addresses must be unmapped
>+			 * because we map physical memory at __PAGE_OFFSET
>+			 * and we don't want to keep aliases.
>+			 */
>+			kpte = lookup_address(addr, &l);
>+			set_pte(kpte, __pte(0));
>+		}
> 	}
> #endif
> }
>-- 
>1.5.3.4
>

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Attachments on bug 441543: 301790 | 301840 | 302107 | 302525