[Xen-changelog] [HVM] Fix a bug in the emulation of the xchg instruction.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 5be9e927533d94ed1389f8926d51c65849133556
# Parent  1dd2062668b2ef87f6dd9df254dc1063944694ac
[HVM] Fix a bug in the emulation of the xchg instruction.

This bug has prevented us from booting fully virtualized SMP guests
that write to the APIC using the xchg instruction (when
CONFIG_X86_GOOD_APIC is not set). On 32 bit platforms, sles 10 kernels
are built without CONFIG_x86_GOOD_APIC not set and hence we have had
problems booting fully virtualized SMP sles 10 guests.

Signed-off-by: K. Y. Srinivasan <ksrinivasan@xxxxxxxxxx>
---
 xen/arch/x86/hvm/io.c       |   10 ++++++++++
 xen/arch/x86/hvm/platform.c |   24 ++++++++++++++++++++----
 2 files changed, 30 insertions(+), 4 deletions(-)

diff -r 1dd2062668b2 -r 5be9e927533d xen/arch/x86/hvm/io.c
--- a/xen/arch/x86/hvm/io.c     Tue May 30 12:28:46 2006 +0100
+++ b/xen/arch/x86/hvm/io.c     Tue May 30 12:30:47 2006 +0100
@@ -648,6 +648,16 @@ static void hvm_mmio_assist(struct vcpu 
             regs->eflags &= ~X86_EFLAGS_CF;
 
         break;
+
+    case INSTR_XCHG:
+       if (src & REGISTER) {
+               index = operand_index(src);
+               set_reg_value(size, index, 0, regs, p->u.data);
+       } else {
+               index = operand_index(dst);
+               set_reg_value(size, index, 0, regs, p->u.data);
+       }
+       break;
     }
 
     hvm_load_cpu_guest_regs(v, regs);
diff -r 1dd2062668b2 -r 5be9e927533d xen/arch/x86/hvm/platform.c
--- a/xen/arch/x86/hvm/platform.c       Tue May 30 12:28:46 2006 +0100
+++ b/xen/arch/x86/hvm/platform.c       Tue May 30 12:30:47 2006 +0100
@@ -954,10 +954,26 @@ void handle_mmio(unsigned long va, unsig
         mmio_opp->instr = mmio_inst.instr;
         mmio_opp->operand[0] = mmio_inst.operand[0]; /* source */
         mmio_opp->operand[1] = mmio_inst.operand[1]; /* destination */
-
-        /* send the request and wait for the value */
-        send_mmio_req(IOREQ_TYPE_XCHG, gpa, 1,
-                      mmio_inst.op_size, 0, IOREQ_WRITE, 0);
+       if (mmio_inst.operand[0] & REGISTER) {
+               long value;
+               unsigned long operand = mmio_inst.operand[0];
+               value = get_reg_value(operand_size(operand), 
+                                     operand_index(operand), 0,
+                                     mmio_opp->inst_decoder_regs);
+               /* send the request and wait for the value */
+               send_mmio_req(IOREQ_TYPE_XCHG, gpa, 1,
+                      mmio_inst.op_size, value, IOREQ_WRITE, 0);
+       } else {
+               /* the destination is a register */
+               long value;
+               unsigned long operand = mmio_inst.operand[1];
+               value = get_reg_value(operand_size(operand), 
+                                     operand_index(operand), 0,
+                                     mmio_opp->inst_decoder_regs);
+               /* send the request and wait for the value */
+               send_mmio_req(IOREQ_TYPE_XCHG, gpa, 1,
+                      mmio_inst.op_size, value, IOREQ_WRITE, 0);
+       }
         break;
 
     default:

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