From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xen.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Jan Beulich <JBeulich@suse.com>
Subject: [PATCH for-next] xen/pv: Construct d0v0's GDT properly
Date: Mon, 16 Oct 2017 15:38:30 +0100 [thread overview]
Message-ID: <1508164710-25970-1-git-send-email-andrew.cooper3@citrix.com> (raw)
c/s cf6d39f8199 "x86/PV: properly populate descriptor tables" changed the GDT
to reference zero_page for intermediate frames between the guest and Xen
frames.
Because dom0_construct_pv() doesn't call arch_set_info_guest(), some bits of
initialisation are missed, including the pv_destroy_gdt() which initially
fills the references to zero_page.
In practice, this means there is a window between starting and the first call
to HYPERCALL_set_gdt() were lar/lsl/verr/verw suffer non-architectural
behaviour.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
This probably wants backporting to Xen 4.7 and later.
---
xen/arch/x86/pv/dom0_build.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/xen/arch/x86/pv/dom0_build.c b/xen/arch/x86/pv/dom0_build.c
index 8ad7e3d..984a94a 100644
--- a/xen/arch/x86/pv/dom0_build.c
+++ b/xen/arch/x86/pv/dom0_build.c
@@ -18,6 +18,7 @@
#include <asm/bzimage.h>
#include <asm/dom0_build.h>
#include <asm/page.h>
+#include <asm/pv/mm.h>
#include <asm/setup.h>
#include "mm.h"
@@ -867,6 +868,13 @@ int __init dom0_construct_pv(struct domain *d,
regs->rsi = vstartinfo_start;
regs->eflags = X86_EFLAGS_IF;
+ /*
+ * We don't call arch_set_info_guest(), so some initialisation needs doing
+ * by hand:
+ * - Reset the GDT to reference zero_page
+ */
+ pv_destroy_gdt(v);
+
if ( test_bit(XENFEAT_supervisor_mode_kernel, parms.f_required) )
panic("Dom0 requires supervisor-mode execution");
--
2.1.4
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next reply other threads:[~2017-10-16 14:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-16 14:38 Andrew Cooper [this message]
2017-10-16 15:58 ` [PATCH for-next] xen/pv: Construct d0v0's GDT properly Jan Beulich
2017-10-16 17:03 ` Andrew Cooper
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