commit b8c6c3683894072f4a8ff910c354c03b65a23464
Author: Knut St. Osmundsen <knut.osmundsen@oracle.com>
Date:   Fri May 29 20:46:11 2026 +0000

    SUPDrv/linux: Kicked out the code for the old KVM init approach. bugref:11093 bugref:10963
    
    svn:sync-xref-src-repo-rev: r174036

diff --git a/src/VBox/HostDrivers/Support/linux/SUPDrv-linux.c b/src/VBox/HostDrivers/Support/linux/SUPDrv-linux.c
index 41f73f61d41..f01446e6909 100644
--- a/src/vboxhost/vboxdrv/linux/SUPDrv-linux.c
+++ b/src/vboxhost/vboxdrv/linux/SUPDrv-linux.c
@@ -1,4 +1,4 @@
-/* $Id: SUPDrv-linux.c 114188 2026-05-27 06:59:16Z knut.osmundsen@oracle.com $ */
+/* $Id: SUPDrv-linux.c 114219 2026-05-29 20:46:11Z knut.osmundsen@oracle.com $ */
 /** @file
  * VBoxDrv - The VirtualBox Support Driver - Linux specifics.
  */
@@ -112,12 +112,6 @@
 # include <linux/fdtable.h>
 # include <linux/kvm_host.h>
 # include <linux/pseudo_fs.h>
-
-#elif RTLNX_VER_RANGE(6,16,0, 7,1,0) && defined(CONFIG_MODULES) && defined(CONFIG_KVM_GENERIC_HARDWARE_ENABLING) && defined(VBOX_WITH_HOST_VMX)
-# if defined(RT_ARCH_AMD64) || defined(RT_ARCH_X86)
-#  include <linux/kvm_host.h>
-#  define SUPDRV_LINUX_HAS_KVM_HWVIRT_API
-# endif
 #endif
 
 
@@ -241,23 +235,7 @@ static struct file_system_type                  g_SupDrvLnxFsType =
     .kill_sb            = kill_anon_super
 };
 # endif /* SUPDRV_LINUX_WITH_DUMMY_KVM_VM_OPENED_VIA_INODE */
-
-#elif defined(SUPDRV_LINUX_HAS_KVM_HWVIRT_API)
-/** Whether we have called kvm_enable_virtualization(). */
-static bool                                     g_fEnabledHwvirtUsingKvm;
-/** Whether we think AMD-V is supported by the CPU. */
-static bool                                     g_fCpuSupportsSvm;
-/** Whether we think VT-x is supported by the CPU. */
-static bool                                     g_fCpuSupportsVmx;
-/** Whether we need to put the corresponding KVM function pointers. */
-static bool                                     g_fPutKvmEnableVirtualization, g_fPutKvmDisableVirtualization;
-/** Function pointer to kvm_enable_virtualization(). */
-static __typeof__(kvm_enable_virtualization)   *g_pfnKvmEnableVirtualization;
-/** Function pointer to kvm_disable_virtualization(). */
-static __typeof__(kvm_disable_virtualization)  *g_pfnKvmDisableVirtualization;
-/** Pointer to the KVM hardware specific module. */
-static struct module                           *g_pKvmHwvirtModule;
-#endif
+#endif /* SUPDRV_LINUX_WITH_DUMMY_KVM_VM */
 
 #if RTLNX_VER_MIN(6,15,0) && (defined(RT_ARCH_AMD64) || defined(RT_ARCH_X86))
 /** Pointer to the switch_fpu_return function. */
@@ -430,7 +408,7 @@ DECLINLINE(RTUID) vboxdrvLinuxEuid(void)
 #endif
 
 
-#if (RTLNX_VER_MIN(6,15,0) || defined(SUPDRV_LINUX_HAS_KVM_HWVIRT_API)) && (defined(RT_ARCH_AMD64) || defined(RT_ARCH_X86))
+#if RTLNX_VER_MIN(6,15,0) && (defined(RT_ARCH_AMD64) || defined(RT_ARCH_X86))
 /**
  * Dynamically resolves a function we need.
  *
@@ -463,116 +441,6 @@ supdrvLinuxFunction(const char *pszModule, const char *pszFunctionNm, PFNRT *ppf
 }
 #endif
 
-#ifdef SUPDRV_LINUX_HAS_KVM_HWVIRT_API
-
-/**
- * This is a hack/workaround that attempts to detect whether
- * kvm_enable_virtualization() is likely to have been called. See
- * @bugref{10963#c14} for details.
- */
-static bool supdrvLinuxIsKvmVirtEnabledLikelyCalled(void)
-{
-    /** @todo Try get address of kvm_usage_count and its mutex via kallsyms_lookup_name()
-      *       which in turn should be looked up by a kprobe. */
-    /*
-     * We don't disable preemption/interrupts here because we assume all CPUs will have
-     * the relevant bits identical in CR4 and EFER.
-     */
-    uint64_t const fVmxeMask = RT_BIT_64(13); /* CR4.VMXE bit. */
-    if (   g_fCpuSupportsVmx
-        && (ASMGetCR4() & fVmxeMask))
-        return true;
-
-    uint32_t const idEfer    = 0xc0000080; /* EFER MSR. */
-    uint64_t const fSvmeMask = RT_BIT_64(12); /* EFER.SVME bit. */
-    if (   g_fCpuSupportsSvm
-        && (ASMRdMsr(idEfer) & fSvmeMask))
-           return true;
-
-    return false;
-}
-
-
-/**
- * Initializes usage of KVM hardware-virtualization symbols.
- */
-static int __init supdrvLinuxInitKvmSymbols(PRTDBGKRNLINFO phKrnlInfo)
-{
-    /*
-     * Figure out the module name first using SUPR0GetVTSupport
-     * and just stop early if we cannot figure out the module name.
-     */
-    uint32_t fCaps = 0;
-    int rc = SUPR0GetVTSupport(&fCaps);
-    g_fCpuSupportsSvm = (fCaps & SUPVTCAPS_AMD_V) || rc == VERR_SVM_NO_SVM;
-    g_fCpuSupportsVmx = (fCaps & SUPVTCAPS_VT_X)  || rc == VERR_VMX_NO_VMX;
-    const char * const pszModName = g_fCpuSupportsVmx ? "kvm_intel"
-                                  : g_fCpuSupportsSvm ? "kvm_amd" : NULL;
-    if (!pszModName)
-    {
-        printk(KERN_WARNING "vboxdrv: Cannot determine KVM module name for this CPU architecture! (%d)\n", rc);
-        return RT_FAILURE(rc) ? rc : VERR_NOT_FOUND;
-    }
-
-    /*
-     * Get the enable & disable functions.
-     */
-    g_fPutKvmEnableVirtualization = supdrvLinuxFunction("kvm", "kvm_enable_virtualization",
-                                                        (PFNRT *)&g_pfnKvmEnableVirtualization, phKrnlInfo);
-    if (g_pfnKvmEnableVirtualization)
-    {
-        g_fPutKvmDisableVirtualization = supdrvLinuxFunction("kvm", "kvm_disable_virtualization",
-                                                             (PFNRT *)&g_pfnKvmDisableVirtualization, phKrnlInfo);
-        if (g_pfnKvmDisableVirtualization)
-        {
-            /*
-             * Try to obtain a reference to kvm_intel/kvm_amd module in addition to the
-             * reference to the kvm module. If we fail, we will not try to use KVM for
-             * enabling/disable hardware-virtualization. This is due a a bug in the Linux
-             * kernel, see @bugref{10963}.
-             *
-             * Note! find_module isn't exported, so we have to temporarily disable the
-             *       indirect branch track machinery in order to call it safely.
-             *       (Setting the SUPPORESS bit to 1 probably won't help much here, as
-             *       the call is done via __x86_indirect_thunk_xxx.)
-             */
-            struct module * (*pfnFindModule)(const char *) = NULL;
-            bool fPutFindModule = supdrvLinuxFunction(NULL, "find_module", (PFNRT *)&pfnFindModule, phKrnlInfo);
-            if (pfnFindModule)
-            {
-                struct module       *pModule;
-                RTLNX_CET_UNSAFE_CALL(pfnFindModule, pModule = pfnFindModule(pszModName));
-                if (fPutFindModule)
-                    symbol_put_addr(pfnFindModule);
-
-                if (pModule)
-                {
-                    if (try_module_get(pModule))
-                    {
-                        g_pKvmHwvirtModule = pModule;
-                        return VINF_SUCCESS;
-                    }
-                    printk(KERN_WARNING "vboxdrv: Failed to obtain reference for the KVM impl module (%s)\n", pszModName);
-                }
-                else
-                    printk(KERN_WARNING "vboxdrv: Failed to find the KVM impl module (%s)\n", pszModName);
-            }
-            if (g_fPutKvmDisableVirtualization)
-                symbol_put_addr(g_pfnKvmDisableVirtualization);
-        }
-        if (g_fPutKvmEnableVirtualization)
-            symbol_put_addr(g_pfnKvmEnableVirtualization);
-    }
-
-    g_pfnKvmDisableVirtualization  = NULL;
-    g_pfnKvmEnableVirtualization   = NULL;
-    g_pKvmHwvirtModule             = NULL;
-    g_fPutKvmEnableVirtualization  = false;
-    g_fPutKvmDisableVirtualization = false;
-    return VERR_NOT_FOUND;
-}
-
-#endif /* SUPDRV_LINUX_HAS_KVM_HWVIRT_API */
 
 /**
  * Initialize module.
@@ -640,23 +508,14 @@ static int __init VBoxDrvLinuxInit(void)
                         /*
                          * Resolve symbols that was made difficult to access with 6.19.
                          */
-#if (defined(SUPDRV_LINUX_HAS_KVM_HWVIRT_API) || RTLNX_VER_MIN(6,15,0)) && (defined(RT_ARCH_AMD64) || defined(RT_ARCH_X86))
+#if RTLNX_VER_MIN(6,15,0) && (defined(RT_ARCH_AMD64) || defined(RT_ARCH_X86))
                         RTDBGKRNLINFO hKrnlInfo = NIL_RTDBGKRNLINFO;
-# if RTLNX_VER_MIN(6,15,0)
                         /* Needed for FPU management. */
                         supdrvLinuxFunction(NULL, "switch_fpu_return",  (PFNRT *)&g_pfnSwitchFpuReturn,  &hKrnlInfo);
-# endif
 # ifdef SUPDRV_LINUX_DYNAMIC_CR4_FUNCTIONS
                         /* Shadow CR4 */
                         supdrvLinuxFunction(NULL, "cr4_update_irqsoff", (PFNRT *)&g_pfnCr4UpdateIrqsoff, &hKrnlInfo);
                         supdrvLinuxFunction(NULL, "cr4_read_shadow",    (PFNRT *)&g_pfnCr4ReadShadow,    &hKrnlInfo);
-# endif
-# ifdef SUPDRV_LINUX_HAS_KVM_HWVIRT_API
-                        int rc2 = supdrvLinuxInitKvmSymbols(&hKrnlInfo);
-                        if (RT_SUCCESS(rc2))
-                            printk(KERN_INFO "vboxdrv: Found KVM hardware-virtualization symbols\n");
-                        else
-                            printk(KERN_WARNING "vboxdrv: Failed to find KVM hardware-virtualization symbols\n");
 # endif
                         if (hKrnlInfo != NIL_RTDBGKRNLINFO)
                             RTR0DbgKrnlInfoRelease(hKrnlInfo);
@@ -726,22 +585,8 @@ static void __exit VBoxDrvLinuxUnload(void)
 #endif
 
     /*
-     * Release symbol and module references.
+     * Release symbol references.
      */
-#ifdef SUPDRV_LINUX_HAS_KVM_HWVIRT_API
-    /* Put the kvm symbols and module. */
-    if (g_fPutKvmEnableVirtualization && g_pfnKvmEnableVirtualization)
-        symbol_put_addr(g_pfnKvmEnableVirtualization);
-    g_pfnKvmEnableVirtualization = NULL;
-    if (g_fPutKvmDisableVirtualization && g_pfnKvmDisableVirtualization)
-        symbol_put_addr(g_pfnKvmDisableVirtualization);
-    if (g_pKvmHwvirtModule)
-    {
-        module_put(g_pKvmHwvirtModule);
-        g_pKvmHwvirtModule = NULL;
-    }
-#endif
-
 #ifdef SUPDRV_LINUX_DYNAMIC_CR4_FUNCTIONS
     /* We don't need to put these, they should be in core_kernel_text(). */
     g_pfnCr4UpdateIrqsoff = NULL;
@@ -2221,39 +2066,10 @@ int VBOXCALL supdrvOSEnableHwvirt(bool fEnable)
     }
     return rc;
 
-#elif defined(SUPDRV_LINUX_HAS_KVM_HWVIRT_API)
-    if (   g_pfnKvmEnableVirtualization
-        && g_pfnKvmDisableVirtualization
-        && supdrvLinuxIsKvmVirtEnabledLikelyCalled())
-    { /* likely */ }
-    else
-        return VERR_NOT_AVAILABLE;
-
-    if (fEnable)
-    {
-        /* kvm_enable_virtualization() is guarded by kvm_usage_count reference counter inside a mutex. */
-        int rc;
-        RTLNX_CET_UNSAFE_CALL(g_pfnKvmEnableVirtualization, rc = g_pfnKvmEnableVirtualization());
-        if (!rc)
-        {
-            g_fEnabledHwvirtUsingKvm = true;
-            printk(KERN_INFO "vboxdrv: Enabled hardware-virtualization using KVM\n");
-            return VINF_SUCCESS;
-        }
-        printk(KERN_ERR "vboxdrv: Failed to enable hardware-virtualization using KVM. rc=%d\n", rc);
-        return VERR_NOT_AVAILABLE;
-    }
-
-    if (g_fEnabledHwvirtUsingKvm)
-    {
-        RTLNX_CET_UNSAFE_CALL(g_pfnKvmDisableVirtualization, g_pfnKvmDisableVirtualization());
-        g_fEnabledHwvirtUsingKvm = false;
-    }
-    return VINF_SUCCESS;
-#else
+#else  /* !SUPDRV_LINUX_WITH_DUMMY_KVM_VM */
     RT_NOREF(fEnable);
     return VERR_NOT_SUPPORTED;
-#endif
+#endif /* !SUPDRV_LINUX_WITH_DUMMY_KVM_VM */
 }
 
 
@@ -2627,7 +2443,7 @@ MODULE_LICENSE("GPL");
 #ifdef MODULE_VERSION
 MODULE_VERSION(VBOX_VERSION_STRING " r" RT_XSTR(VBOX_SVN_REV) " (" RT_XSTR(SUPDRV_IOC_VERSION) ")");
 #endif
-#ifdef SUPDRV_LINUX_HAS_KVM_HWVIRT_API
+#ifdef SUPDRV_LINUX_WITH_DUMMY_KVM_VM
 MODULE_SOFTDEP("pre: kvm_intel kvm_amd");
 #endif