[xen master] x86/vmx: Use asm goto() in _vmx_cpu_up()

[patchbot@xxxxxxx]

commit 350d63eff60860de4b9c72926ca6126701aaf03c
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Apr 1 23:56:46 2025 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Apr 2 13:16:27 2025 +0100

    x86/vmx: Use asm goto() in _vmx_cpu_up()
    
    With the new toolchain baseline, we can make use of asm goto() in certain
    places, and the VMXON invocation is one example.
    
    This removes the logic to set up rc (including a fixup section where 
bactraces
    have no connection to the invoking function), the logic to decode it,
    including the default case which was dead but not visibly-so to the 
compiler.
    
    No functional change.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmcs.c            | 51 ++++++++++++++++++----------------
 xen/arch/x86/include/asm/hvm/vmx/vmx.h | 19 -------------
 2 files changed, 27 insertions(+), 43 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 0ba65becec..1d427100ce 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -749,30 +749,15 @@ static int _vmx_cpu_up(bool bsp)
     if ( bsp && (rc = vmx_cpu_up_prepare(cpu)) != 0 )
         return rc;
 
-    switch ( __vmxon(this_cpu(vmxon_region)) )
-    {
-    case -2: /* #UD or #GP */
-        if ( bios_locked &&
-             test_bit(X86_FEATURE_SMX, &boot_cpu_data.x86_capability) &&
-             (!(eax & IA32_FEATURE_CONTROL_ENABLE_VMXON_OUTSIDE_SMX) ||
-              !(eax & IA32_FEATURE_CONTROL_ENABLE_VMXON_INSIDE_SMX)) )
-        {
-            printk("CPU%d: VMXON failed: perhaps because of TXT settings "
-                   "in your BIOS configuration?\n", cpu);
-            printk(" --> Disable TXT in your BIOS unless using a secure "
-                   "bootloader.\n");
-            return -EINVAL;
-        }
-        /* fall through */
-    case -1: /* CF==1 or ZF==1 */
-        printk("CPU%d: unexpected VMXON failure\n", cpu);
-        return -EINVAL;
-    case 0: /* success */
-        this_cpu(vmxon) = 1;
-        break;
-    default:
-        BUG();
-    }
+    asm goto ( "1: vmxon %[addr]\n\t"
+               "   jbe %l[vmxon_fail]\n\t"
+               _ASM_EXTABLE(1b, %l[vmxon_fault])
+               :
+               : [addr] "m" (this_cpu(vmxon_region))
+               : "memory"
+               : vmxon_fail, vmxon_fault );
+
+    this_cpu(vmxon) = 1;
 
     hvm_asid_init(cpu_has_vmx_vpid ? (1u << VMCS_VPID_WIDTH) : 0);
 
@@ -785,6 +770,24 @@ static int _vmx_cpu_up(bool bsp)
     vmx_pi_per_cpu_init(cpu);
 
     return 0;
+
+ vmxon_fault:
+    if ( bios_locked &&
+         test_bit(X86_FEATURE_SMX, &boot_cpu_data.x86_capability) &&
+         (!(eax & IA32_FEATURE_CONTROL_ENABLE_VMXON_OUTSIDE_SMX) ||
+          !(eax & IA32_FEATURE_CONTROL_ENABLE_VMXON_INSIDE_SMX)) )
+    {
+        printk(XENLOG_ERR
+               "CPU%d: VMXON failed: perhaps because of TXT settings in your 
BIOS configuration?\n",
+               cpu);
+        printk(XENLOG_ERR
+               " --> Disable TXT in your BIOS unless using a secure 
bootloader.\n");
+        return -EINVAL;
+    }
+
+ vmxon_fail:
+    printk(XENLOG_ERR "CPU%d: unexpected VMXON failure\n", cpu);
+    return -EINVAL;
 }
 
 int cf_check vmx_cpu_up(void)
diff --git a/xen/arch/x86/include/asm/hvm/vmx/vmx.h 
b/xen/arch/x86/include/asm/hvm/vmx/vmx.h
index 843f8591b9..7c6ba73407 100644
--- a/xen/arch/x86/include/asm/hvm/vmx/vmx.h
+++ b/xen/arch/x86/include/asm/hvm/vmx/vmx.h
@@ -559,25 +559,6 @@ static inline void __vmxoff(void)
         : : : "memory" );
 }
 
-static inline int __vmxon(u64 addr)
-{
-    int rc;
-
-    asm volatile ( 
-        "1: " VMXON_OPCODE MODRM_EAX_06 "\n"
-        "   setna %b0 ; neg %0\n" /* CF==1 or ZF==1 --> rc = -1 */
-        "2:\n"
-        ".section .fixup,\"ax\"\n"
-        "3: sub $2,%0 ; jmp 2b\n"    /* #UD or #GP --> rc = -2 */
-        ".previous\n"
-        _ASM_EXTABLE(1b, 3b)
-        : "=q" (rc)
-        : "0" (0), "a" (&addr)
-        : "memory");
-
-    return rc;
-}
-
 int cf_check vmx_guest_x86_mode(struct vcpu *v);
 unsigned int vmx_get_cpl(void);
 
--
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