Dispatch from the guest_{rd,wr}msr() functions, after falling through from the
!is_viridian_domain() case.

Rename {rd,wr}msr_hypervisor_regs() to guest_{rd,wr}msr_xen() for consistency,
and because the _regs suffix isn't very appropriate.

Update them to take a vcpu pointer rather than presuming that they act on
current, and switch to using X86EMUL_* return values.

Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
Reviewed-by: Kevin Tian <kevin.t...@intel.com>
Reviewed-by: Roger Pau Monné <roger....@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
CC: Paul Durrant <paul.durr...@citrix.com>
CC: Wei Liu <wei.l...@citrix.com>
CC: Sergey Dyasli <sergey.dya...@citrix.com>

v2:
 * Introduce some constants for the hypervisor range.  However, I do not think
   the current code is an improvement over bare numbers.
---
 xen/arch/x86/hvm/svm/svm.c      | 25 ++++---------------------
 xen/arch/x86/hvm/vmx/vmx.c      | 24 ++++--------------------
 xen/arch/x86/msr.c              |  8 ++++++++
 xen/arch/x86/pv/emul-priv-op.c  |  6 ------
 xen/arch/x86/traps.c            | 36 ++++++++++++++++++------------------
 xen/include/asm-x86/msr-index.h |  2 ++
 xen/include/asm-x86/processor.h |  4 ++--
 7 files changed, 38 insertions(+), 67 deletions(-)

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index e8ac2d8..dadf92d 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1966,9 +1966,6 @@ static int svm_msr_read_intercept(unsigned int msr, 
uint64_t *msr_content)
         else if ( ret )
             break;
 
-        if ( rdmsr_hypervisor_regs(msr, msr_content) )
-            break;
-
         if ( rdmsr_safe(msr, *msr_content) == 0 )
             break;
 
@@ -2121,25 +2118,11 @@ static int svm_msr_write_intercept(unsigned int msr, 
uint64_t msr_content)
         else if ( ret )
             break;
 
-        switch ( wrmsr_hypervisor_regs(msr, msr_content) )
-        {
-        case -ERESTART:
-            result = X86EMUL_RETRY;
-            break;
-        case 0:
-            /*
-             * Match up with the RDMSR side for now; ultimately this entire
-             * case block should go away.
-             */
-            if ( rdmsr_safe(msr, msr_content) == 0 )
-                break;
-            goto gpf;
-        case 1:
+        /* Match up with the RDMSR side; ultimately this should go away. */
+        if ( rdmsr_safe(msr, msr_content) == 0 )
             break;
-        default:
-            goto gpf;
-        }
-        break;
+
+        goto gpf;
     }
 
     if ( sync )
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 5fc21a5..b9157af 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2909,9 +2909,6 @@ static int vmx_msr_read_intercept(unsigned int msr, 
uint64_t *msr_content)
             break;
         }
 
-        if ( rdmsr_hypervisor_regs(msr, msr_content) )
-            break;
-
         if ( rdmsr_safe(msr, *msr_content) == 0 )
             break;
 
@@ -3153,24 +3150,11 @@ static int vmx_msr_write_intercept(unsigned int msr, 
uint64_t msr_content)
              is_last_branch_msr(msr) )
             break;
 
-        switch ( wrmsr_hypervisor_regs(msr, msr_content) )
-        {
-        case -ERESTART:
-            return X86EMUL_RETRY;
-        case 0:
-            /*
-             * Match up with the RDMSR side for now; ultimately this
-             * entire case block should go away.
-             */
-            if ( rdmsr_safe(msr, msr_content) == 0 )
-                break;
-            goto gp_fault;
-        case 1:
+        /* Match up with the RDMSR side; ultimately this should go away. */
+        if ( rdmsr_safe(msr, msr_content) == 0 )
             break;
-        default:
-            goto gp_fault;
-        }
-        break;
+
+        goto gp_fault;
     }
 
     return X86EMUL_OKAY;
diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 2fc2021..62079bb 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -185,6 +185,10 @@ int guest_rdmsr(const struct vcpu *v, uint32_t msr, 
uint64_t *val)
         }
 
         /* Fallthrough. */
+    case MSR_XEN_ALT_START ... MSR_XEN_ALT_START + NR_XEN_MSRS - 1:
+        ret = guest_rdmsr_xen(v, msr, val);
+        goto out;
+
     default:
         return X86EMUL_UNHANDLEABLE;
     }
@@ -276,6 +280,10 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
         }
 
         /* Fallthrough. */
+    case MSR_XEN_ALT_START ... MSR_XEN_ALT_START + NR_XEN_MSRS - 1:
+        ret = guest_wrmsr_xen(v, msr, val);
+        goto out;
+
     default:
         return X86EMUL_UNHANDLEABLE;
     }
diff --git a/xen/arch/x86/pv/emul-priv-op.c b/xen/arch/x86/pv/emul-priv-op.c
index ecb3b9c..9ddc5ca 100644
--- a/xen/arch/x86/pv/emul-priv-op.c
+++ b/xen/arch/x86/pv/emul-priv-op.c
@@ -974,9 +974,6 @@ static int read_msr(unsigned int reg, uint64_t *val,
         }
         /* fall through */
     default:
-        if ( rdmsr_hypervisor_regs(reg, val) )
-            return X86EMUL_OKAY;
-
         rc = vmce_rdmsr(reg, val);
         if ( rc < 0 )
             break;
@@ -1173,9 +1170,6 @@ static int write_msr(unsigned int reg, uint64_t val,
         }
         /* fall through */
     default:
-        if ( wrmsr_hypervisor_regs(reg, val) == 1 )
-            return X86EMUL_OKAY;
-
         rc = vmce_wrmsr(reg, val);
         if ( rc < 0 )
             break;
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 19bc174..ea6b17c 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -777,31 +777,29 @@ static void do_trap(struct cpu_user_regs *regs)
           trapnr, trapstr(trapnr), regs->error_code);
 }
 
-/* Returns 0 if not handled, and non-0 for success. */
-int rdmsr_hypervisor_regs(uint32_t idx, uint64_t *val)
+int guest_rdmsr_xen(const struct vcpu *v, uint32_t idx, uint64_t *val)
 {
-    struct domain *d = current->domain;
+    const struct domain *d = v->domain;
     /* Optionally shift out of the way of Viridian architectural MSRs. */
-    uint32_t base = is_viridian_domain(d) ? 0x40000200 : 0x40000000;
+    uint32_t base = (is_viridian_domain(d)
+                     ? MSR_XEN_ALT_START : MSR_HYPERVISOR_START);
 
     switch ( idx - base )
     {
     case 0: /* Write hypercall page MSR.  Read as zero. */
-    {
         *val = 0;
-        return 1;
-    }
+        return X86EMUL_OKAY;
     }
 
-    return 0;
+    return X86EMUL_EXCEPTION;
 }
 
-/* Returns 1 if handled, 0 if not and -Exx for error. */
-int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
+int guest_wrmsr_xen(struct vcpu *v, uint32_t idx, uint64_t val)
 {
-    struct domain *d = current->domain;
+    struct domain *d = v->domain;
     /* Optionally shift out of the way of Viridian architectural MSRs. */
-    uint32_t base = is_viridian_domain(d) ? 0x40000200 : 0x40000000;
+    uint32_t base = (is_viridian_domain(d)
+                     ? MSR_XEN_ALT_START : MSR_HYPERVISOR_START);
 
     switch ( idx - base )
     {
@@ -818,7 +816,7 @@ int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
             gdprintk(XENLOG_WARNING,
                      "wrmsr hypercall page index %#x unsupported\n",
                      page_index);
-            return 0;
+            goto gp_fault;
         }
 
         page = get_page_from_gfn(d, gmfn, &t, P2M_ALLOC);
@@ -831,13 +829,13 @@ int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
             if ( p2m_is_paging(t) )
             {
                 p2m_mem_paging_populate(d, gmfn);
-                return -ERESTART;
+                return X86EMUL_RETRY;
             }
 
             gdprintk(XENLOG_WARNING,
                      "Bad GMFN %lx (MFN %lx) to MSR %08x\n",
                      gmfn, page ? page_to_mfn(page) : -1UL, base);
-            return 0;
+            goto gp_fault;
         }
 
         hypercall_page = __map_domain_page(page);
@@ -845,11 +843,12 @@ int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
         unmap_domain_page(hypercall_page);
 
         put_page_and_type(page);
-        return 1;
+        return X86EMUL_OKAY;
     }
     }
 
-    return 0;
+ gp_fault:
+    return X86EMUL_EXCEPTION;
 }
 
 void cpuid_hypervisor_leaves(const struct vcpu *v, uint32_t leaf,
@@ -887,7 +886,8 @@ void cpuid_hypervisor_leaves(const struct vcpu *v, uint32_t 
leaf,
     case 2:
         res->a = 1;            /* Number of hypercall-transfer pages */
                                /* MSR base address */
-        res->b = is_viridian_domain(d) ? 0x40000200 : 0x40000000;
+        res->b = (is_viridian_domain(d)
+                  ? MSR_XEN_ALT_START : MSR_HYPERVISOR_START);
         if ( is_pv_domain(d) ) /* Features */
             res->c |= XEN_CPUID_FEAT1_MMU_PT_UPDATE_PRESERVE_AD;
         break;
diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index ee029a2..2b4014c 100644
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -543,5 +543,7 @@
 /* Hypervisor leaves in the 0x4xxxxxxx range. */
 #define MSR_HYPERVISOR_START            0x40000000
 #define NR_VIRIDIAN_MSRS                0x00000200
+#define MSR_XEN_ALT_START               0x40000200
+#define NR_XEN_MSRS                     0x00000100
 
 #endif /* __ASM_MSR_INDEX_H */
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 01bc89f..28f2db6 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -519,8 +519,8 @@ unsigned long alloc_stub_page(unsigned int cpu, unsigned 
long *mfn);
 
 void cpuid_hypervisor_leaves(const struct vcpu *v, uint32_t leaf,
                              uint32_t subleaf, struct cpuid_leaf *res);
-int rdmsr_hypervisor_regs(uint32_t idx, uint64_t *val);
-int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val);
+int guest_rdmsr_xen(const struct vcpu *v, uint32_t idx, uint64_t *val);
+int guest_wrmsr_xen(struct vcpu *v, uint32_t idx, uint64_t val);
 
 void microcode_set_module(unsigned int);
 int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void), unsigned long len);
-- 
2.1.4


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