linux-kernel - [PATCH v2 4/6] x86-64/xen: Enable the vvar mapping

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Message-Id: <4659478ed2f3480938f96491c2ecbe2b2e113a23.1312378163.git.luto@mit.edu>
Date:	Wed,  3 Aug 2011 09:31:52 -0400
From:	Andy Lutomirski <luto@....EDU>
To:	x86@...nel.org, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	jeremy@...p.org, keir.xen@...il.com, xen-devel@...ts.xensource.com,
	virtualization@...ts.linux-foundation.org,
	Andy Lutomirski <luto@....edu>
Subject: [PATCH v2 4/6] x86-64/xen: Enable the vvar mapping

Xen needs to handle VVAR_PAGE, introduced in git commit:
9fd67b4ed0714ab718f1f9bd14c344af336a6df7
x86-64: Give vvars their own page

Otherwise we die during bootup with a message like:

(XEN) mm.c:940:d10 Error getting mfn 1888 (pfn 1e3e48) from L1 entry
      8000000001888465 for l1e_owner=10, pg_owner=10
(XEN) mm.c:5049:d10 ptwr_emulate: could not get_page_from_l1e()
[    0.000000] BUG: unable to handle kernel NULL pointer dereference at (null)
[    0.000000] IP: [<ffffffff8103a930>] xen_set_pte+0x20/0xe0

Signed-off-by: Andy Lutomirski <luto@....edu>
Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---
 arch/x86/xen/mmu.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index f987bde..8cce339 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1916,6 +1916,7 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
 # endif
 #else
 	case VSYSCALL_LAST_PAGE ... VSYSCALL_FIRST_PAGE:
+	case VVAR_PAGE:
 #endif
 	case FIX_TEXT_POKE0:
 	case FIX_TEXT_POKE1:
@@ -1956,7 +1957,8 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
 #ifdef CONFIG_X86_64
 	/* Replicate changes to map the vsyscall page into the user
 	   pagetable vsyscall mapping. */
-	if (idx >= VSYSCALL_LAST_PAGE && idx <= VSYSCALL_FIRST_PAGE) {
+	if ((idx >= VSYSCALL_LAST_PAGE && idx <= VSYSCALL_FIRST_PAGE) ||
+	    idx == VVAR_PAGE) {
 		unsigned long vaddr = __fix_to_virt(idx);
 		set_pte_vaddr_pud(level3_user_vsyscall, vaddr, pte);
 	}
-- 
1.7.6

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