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Re: [Xen-devel] [PATCH v4 04/16] xen: Add is_vmware_port_enabled



On 09/11/2014 02:36 PM, Don Slutz wrote:
  int __get_instruction_length_from_list(struct vcpu *v,
-        const enum instruction_index *list, unsigned int list_count)
+                                       const enum instruction_index *list,
+                                       unsigned int list_count,
+                                       bool_t err_rpt)
  {
      struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
      unsigned int i, j, inst_len = 0;
@@ -211,10 +222,13 @@ int __get_instruction_length_from_list(struct vcpu *v,
      mismatch: ;
      }
- gdprintk(XENLOG_WARNING,
-             "%s: Mismatch between expected and actual instruction bytes: "
-             "eip = %lx\n",  __func__, (unsigned long)vmcb->rip);
-    hvm_inject_hw_exception(TRAP_gp_fault, 0);
+    if ( err_rpt )
+    {
+        gdprintk(XENLOG_WARNING,
+                 "%s: Mismatch between expected and actual instruction bytes: "
+                 "eip = %lx\n",  __func__, (unsigned long)vmcb->rip);
+        hvm_inject_hw_exception(TRAP_gp_fault, 0);
+    }
      return 0;
done:
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index b5188e6..9e14d2a 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -59,6 +59,7 @@
  #include <public/sched.h>
  #include <asm/hvm/vpt.h>
  #include <asm/hvm/trace.h>
+#include <asm/hvm/vmport.h>
  #include <asm/hap.h>
  #include <asm/apic.h>
  #include <asm/debugger.h>
@@ -2065,6 +2066,38 @@ svm_vmexit_do_vmsave(struct vmcb_struct *vmcb,
      return;
  }
+static void svm_vmexit_gp_intercept(struct cpu_user_regs *regs,
+                                    struct vcpu *v)
+{
+    struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
+    unsigned long inst_len;
+    unsigned long inst_addr = svm_rip2pointer(v);
+    int rc;
+    static const enum instruction_index list[] = {
+        INSTR_INL_DX, INSTR_INB_DX, INSTR_OUTL_DX, INSTR_OUTB_DX
+    };
+
+    inst_len = __get_instruction_length_from_list(
+        v, list, ARRAY_SIZE(list), 0);

I should have asked earlier but I don't think I understand why the last argument here is 0 (and therefore why you have this last argument at all).

Because whether or not you are warning in __get_instruction_length_from_list() it will still return 0. And that, in turn, will cause vmport_gp_check() to return an error. And then you will print another warning in VMPORT_LOG. So there is a warning anyway.

Second, since this handler appears to be handling #GP only for VMware guest we should make sure that it is not executed for any other guest. You do now condition intercept got #GP for such guests only but I still think having a check here is worth doing. Maybe a BUG() or ASSERT()?

The same comments are applicable to VMX code, I suspect.

+
+    rc = vmport_gp_check(regs, v, inst_len, inst_addr,
+                         vmcb->exitinfo1, vmcb->exitinfo2);
+    if ( !rc )
+        __update_guest_eip(regs, inst_len);
+    else
+    {
+        VMPORT_DBG_LOG(VMPORT_LOG_GP_UNKNOWN,
+                       "gp: rc=%d ei1=0x%lx ei2=0x%lx ip=%"PRIx64
+                       " (0x%lx,%ld) ax=%"PRIx64" bx=%"PRIx64" cx=%"PRIx64
+                       " dx=%"PRIx64" si=%"PRIx64" di=%"PRIx64, rc,
+                       (unsigned long)vmcb->exitinfo1,
+                       (unsigned long)vmcb->exitinfo2, regs->rip, inst_addr,
+                       inst_len, regs->rax, regs->rbx, regs->rcx, regs->rdx,
+                       regs->rsi, regs->rdi);
+        hvm_inject_hw_exception(TRAP_gp_fault, regs->error_code);
+    }
+}
+

...

+
+int vmport_gp_check(struct cpu_user_regs *regs, struct vcpu *v,
+                    unsigned long inst_len, unsigned long inst_addr,
+                    unsigned long ei1, unsigned long ei2)
+{
+    if ( !v->domain->arch.hvm_domain.is_vmware_port_enabled )
+        return 10;
+
+    if ( inst_len && inst_len <= 2 && get_low_bits(regs->rdx) == BDOOR_PORT &&
+         ei1 == 0 && ei2 == 0 && regs->error_code == 0 &&
+         (uint32_t)regs->rax == BDOOR_MAGIC )
+    {
+        int i = 0;
+        uint32_t val;
+        uint32_t byte_cnt = 4;
+        unsigned char bytes[2];
+        unsigned int fetch_len;
+        int frc;
+        int rc;
+
+        /*
+         * Fetch up to the next page break; we'll fetch from the
+         * next page later if we have to.
+         */
+        fetch_len = min_t(unsigned int, inst_len,
+                          PAGE_SIZE - (inst_addr  & ~PAGE_MASK));
+        frc = hvm_fetch_from_guest_virt_nofault(bytes, inst_addr, fetch_len,
+                                                PFEC_page_present);
+        if ( frc != HVMCOPY_okay )
+        {
+            gdprintk(XENLOG_WARNING,
+                     "Bad instruction fetch at %#lx (frc=%d il=%lu fl=%u)\n",
+                     (unsigned long) inst_addr, frc, inst_len, fetch_len);
+            return 11;
+        }
+        if ( bytes[0] == 0x66 )     /* operand size prefix */
+        {
+            byte_cnt = 2;
+            i = 1;
+            if ( fetch_len != inst_len )
+            {
+                frc = hvm_fetch_from_guest_virt_nofault(&bytes[1],
+                                                        inst_addr + 1, 1,
+                                                        PFEC_page_present);
+                if ( frc != HVMCOPY_okay )
+                {
+                    gdprintk(XENLOG_WARNING,
+                             "Bad instruction fetch at %#lx + 1 (frc=%d)\n",
+                             (unsigned long) inst_addr, frc);
+                    return 12;
+                }
+            }
+        }
+        if ( bytes[i] == 0xed )     /* in (%dx),%eax or in (%dx),%ax */
+        {
+            rc = vmport_ioport(IOREQ_READ, BDOOR_PORT, byte_cnt, &val);
+            VMPORT_DBG_LOG(VMPORT_LOG_GP_VMWARE_AFTER,
+                           "gp: VMwareIn  rc=%d ip=%"PRIx64" byte_cnt=%d ax=%"
+                           PRIx64" bx=%"PRIx64" cx=%"PRIx64" dx=%"PRIx64
+                           " si=%"PRIx64" di=%"PRIx64, rc,
+                           inst_addr, byte_cnt, regs->rax, regs->rbx,
+                           regs->rcx, regs->rdx, regs->rsi, regs->rdi);
+            return rc;
+        }
+        else if ( bytes[i] == 0xec )     /* in (%dx),%al */
+        {
+            rc = vmport_ioport(IOREQ_READ, BDOOR_PORT, 1, &val);
+            VMPORT_DBG_LOG(VMPORT_LOG_GP_VMWARE_AFTER,
+                           "gp: VMwareIn  rc=%d ip=%"PRIx64" byte_cnt=1 ax=%"
+                           PRIx64" bx=%"PRIx64" cx=%"PRIx64" dx=%"PRIx64
+                           " si=%"PRIx64" di=%"PRIx64, rc,
+                           inst_addr, regs->rax, regs->rbx, regs->rcx,
+                           regs->rdx, regs->rsi, regs->rdi);
+            return rc;
+        }
+        else if ( bytes[i] == 0xef )     /* out %eax,(%dx) or out %ax,(%dx) */
+        {
+            rc = vmport_ioport(IOREQ_WRITE, BDOOR_PORT, byte_cnt, &val);
+            VMPORT_DBG_LOG(VMPORT_LOG_GP_VMWARE_AFTER,
+                           "gp: VMwareOut rc=%d ip=%"PRIx64" byte_cnt=%d ax=%"
+                           PRIx64" bx=%"PRIx64" cx=%"PRIx64" dx=%"PRIx64
+                           " si=%"PRIx64" di=%"PRIx64, rc,
+                           inst_addr, byte_cnt, regs->rax, regs->rbx,
+                           regs->rcx, regs->rdx, regs->rsi, regs->rdi);
+            return rc;
+        }
+        else if ( bytes[i] == 0xee )     /* out %al,(%dx) */
+        {
+            rc = vmport_ioport(IOREQ_WRITE, BDOOR_PORT, 1, &val);
+            VMPORT_DBG_LOG(VMPORT_LOG_GP_VMWARE_AFTER,
+                           "gp: VMwareOut rc=%d ip=%"PRIx64" byte_cnt=1 ax=%"
+                           PRIx64" bx=%"PRIx64" cx=%"PRIx64" dx=%"PRIx64
+                           " si=%"PRIx64" di=%"PRIx64, rc,
+                           inst_addr, regs->rax, regs->rbx, regs->rcx,
+                           regs->rdx, regs->rsi, regs->rdi);
+            return rc;
+        }
+        else
+        {
+            VMPORT_DBG_LOG(VMPORT_LOG_GP_FAIL_RD_INST,
+                           "gp: VMware? lip=%"PRIx64"[%d]=>0x%x(%ld) ax=%"
+                           PRIx64" bx=%"PRIx64" cx=%"PRIx64" dx=%"PRIx64
+                           " si=%"PRIx64" di=%"PRIx64,
+                           inst_addr, i, bytes[i], inst_len, regs->rax,
+                           regs->rbx, regs->rcx, regs->rdx, regs->rsi,
+                           regs->rdi);
+            return 13;
+        }
+    }
+    return 14;

The return values should be defined as macros --- otherwise they look like some magic integers.

-boris



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