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[Xen-devel] Re: [RFC PATCH 16/33] Add support for Xen to entry.S.

Chris Wright wrote:
* Rusty Russell (rusty@xxxxxxxxxxxxxxx) wrote:
On Tue, 2006-07-18 at 00:00 -0700, Chris Wright wrote:
plain text document attachment (i386-entry.S)
- change cli/sti
- change test for user mode return to work for kernel mode in ring1
- check hypervisor saved event mask on return from exception
- add entry points for the hypervisor upcall handlers
- avoid math emulation check when running on Xen
- add nmi handler for running on Xen

Signed-off-by: Ian Pratt <ian.pratt@xxxxxxxxxxxxx>
Signed-off-by: Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>

 arch/i386/kernel/asm-offsets.c |   26 +++++++
 arch/i386/kernel/entry.S       |  141 ++++++++++++++++++++++++++++++++++++-----
 arch/i386/mach-xen/setup-xen.c |   19 +++++
 drivers/xen/core/features.c    |    2
 4 files changed, 169 insertions(+), 19 deletions(-)

diff -r 5cca1805b8a7 arch/i386/kernel/entry.S
--- a/arch/i386/kernel/entry.S  Tue Jul 18 02:20:39 2006 -0400
+++ b/arch/i386/kernel/entry.S  Tue Jul 18 02:22:56 2006 -0400
@@ -76,8 +76,39 @@ NT_MASK              = 0x00004000
 NT_MASK                = 0x00004000
 VM_MASK                = 0x00020000
+#ifndef CONFIG_XEN
+#define DISABLE_INTERRUPTS     cli
+#define ENABLE_INTERRUPTS      sti
+#include <xen/interface/xen.h>
+EVENT_MASK     = 0x2E
+/* Offsets into shared_info_t. */
+#define evtchn_upcall_pending          /* 0 */
+#define evtchn_upcall_mask             1
Erk... Can we get these into asm-offsets?

Hmm, we put the vcpu shift in, guess we missed that.  Thanks for noticing.

+#ifdef CONFIG_SMP
+/* Set %esi to point to the appropriate vcpu structure */
+#define GET_VCPU_INFO          movl TI_cpu(%ebp),%esi                  ; \
+                               shl  $SIZEOF_VCPU_INFO_SHIFT,%esi       ; \
+                               addl HYPERVISOR_shared_info,%esi
+#define GET_VCPU_INFO          movl HYPERVISOR_shared_info,%esi
+/* The following end up using/clobbering %esi, because of GET_VCPU_INFO */
+#define __DISABLE_INTERRUPTS   movb $1,evtchn_upcall_mask(%esi)
+#define DISABLE_INTERRUPTS     GET_VCPU_INFO                           ; \
+                               __DISABLE_INTERRUPTS
+#define ENABLE_INTERRUPTS      GET_VCPU_INFO                           ; \
+                               movb $0,evtchn_upcall_mask(%esi)
+#define __TEST_PENDING         testb $0xFF,evtchn_upcall_pending(%esi)
Actually, is it possible to move these to a header somewhere?  In the
paravirt_ops patches I used the names CLI and STI (copied from the VMI
patches), but didn't allow them to clobber any regs.  They're defined in

Sure, although it's only used here.  Got a preference?

It might be an idea to use something other than STI, CLI and CPUID, since the assembler is case-insensitive. We've already had one bug where CPUID didn't get replaced and the assembler quietly accepted it as-is.


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