[gentoo-commits] gentoo-x86 commit in x11-drivers/nvidia-drivers/files: NVIDIA_kernel-96.43.05-2290218.diff

[Mike Frysinger (vapier)]

vapier      08/04/18 19:54:05

  Added:                NVIDIA_kernel-96.43.05-2290218.diff
  Log:
  Add fix from upstream for building with linux-2.6.25 #218178.
  (Portage version: 2.2_pre5)

Revision  Changes    Path
1.1                  x11-drivers/nvidia-drivers/files/NVIDIA_kernel-96.43.05-2290218.diff

file : http://sources.gentoo.org/viewcvs.py/gentoo-x86/x11-drivers/nvidia-drivers/files/NVIDIA_kernel-96.43.05-2290218.diff?rev=1.1&view=markup
plain: http://sources.gentoo.org/viewcvs.py/gentoo-x86/x11-drivers/nvidia-drivers/files/NVIDIA_kernel-96.43.05-2290218.diff?rev=1.1&content-type=text/plain

Index: NVIDIA_kernel-96.43.05-2290218.diff
===================================================================
http://www.nvnews.net/vbulletin/showthread.php?t=110088
http://bugs.gentoo.org/218178

diff -ru usr/src/nv/Makefile.kbuild usr/src/nv.2290218/Makefile.kbuild
--- usr/src/nv/Makefile.kbuild	2008-01-22 20:12:23.000000000 -0800
+++ usr/src/nv.2290218/Makefile.kbuild	2008-03-18 13:15:30.394522179 -0700
@@ -177,6 +177,7 @@
 	vmap \
 	signal_struct \
 	agp_backend_acquire \
+	set_pages_uc \
 	change_page_attr \
 	pci_get_class \
 	sysctl_max_map_count \
diff -ru usr/src/nv/conftest.sh usr/src/nv.2290218/conftest.sh
--- usr/src/nv/conftest.sh	2008-01-22 20:12:23.000000000 -0800
+++ usr/src/nv.2290218/conftest.sh	2008-03-18 13:15:32.710654166 -0700
@@ -100,6 +100,32 @@
             fi
         ;;
 
+        set_pages_uc)
+            #
+            # Determine if the set_pages_uc() function is present.
+            #
+            echo "#include <linux/autoconf.h>
+            #include <asm/cacheflush.h>
+            void conftest_set_pages_uc(void) {
+                set_pages_uc();
+            }" > conftest$$.c
+
+            $CC $CFLAGS -c conftest$$.c > /dev/null 2>&1
+            rm -f conftest$$.c
+
+            if [ -f conftest$$.o ]; then
+                rm -f conftest$$.o
+                echo "#undef NV_SET_PAGES_UC_PRESENT" >> conftest.h
+                return
+            else
+                echo "#ifdef NV_CHANGE_PAGE_ATTR_PRESENT" >> conftest.h
+                echo "#undef NV_CHANGE_PAGE_ATTR_PRESENT" >> conftest.h
+                echo "#endif"                             >> conftest.h
+                echo "#define NV_SET_PAGES_UC_PRESENT"    >> conftest.h
+                return
+            fi
+        ;;
+
         change_page_attr)
             #
             # Determine if the change_page_attr() function is
@@ -124,7 +150,9 @@
                 rm -f conftest$$.o
                 return
             else
+                echo "#ifndef NV_SET_PAGES_UC_PRESENT"     >> conftest.h
                 echo "#define NV_CHANGE_PAGE_ATTR_PRESENT" >> conftest.h
+                echo "#endif"                              >> conftest.h
                 return
             fi
         ;;
@@ -501,6 +529,8 @@
                 return
             fi
 
+            rm -f conftest$$.o
+
             echo "#include <linux/autoconf.h>
             #include <linux/interrupt.h>
             irq_handler_t conftest_isr;
diff -ru usr/src/nv/nv-linux.h usr/src/nv.2290218/nv-linux.h
--- usr/src/nv/nv-linux.h	2008-01-22 20:12:23.000000000 -0800
+++ usr/src/nv.2290218/nv-linux.h	2008-03-18 13:15:26.674310174 -0700
@@ -808,9 +808,10 @@
 
 #define NV_PGD_OFFSET(address, kernel, mm)              \
    ({                                                   \
+        struct mm_struct *__mm = (mm);                  \
         pgd_t *__pgd;                                   \
         if (!kernel)                                    \
-            __pgd = pgd_offset(mm, address);            \
+            __pgd = pgd_offset(__mm, address);          \
         else                                            \
             __pgd = pgd_offset_k(address);              \
         __pgd;                                          \
@@ -1097,21 +1098,24 @@
 #define NV_ATOMIC_DEC_AND_TEST(data)    atomic_dec_and_test(&(data))
 #define NV_ATOMIC_READ(data)            atomic_read(&(data))
 
+extern int nv_update_memory_types;
+
 /*
- * a BUG() is triggered on early 2.6 x86_64 kernels. the underlying
- * problem actually exists on many architectures and kernels, but
- * these are the only kernels that check the condition and trigger
- * a BUG(). note that this is a problem of the core kernel, not an
- * nvidia bug (and can still be triggered by agpgart). let's avoid
- * change_page_attr on those kernels.
+ * Using change_page_attr() on early Linux/x86-64 2.6 kernels may
+ * result in a BUG() being triggered. The underlying problem
+ * actually exists on multiple architectures and kernels, but only
+ * the above check for the condition and trigger a BUG().
+ *
+ * Note that this is a due to a bug in the Linux kernel, not an
+ * NVIDIA driver bug (it can also be triggered by AGPGART).
+ *
+ * We therefore need to determine at runtime if change_page_attr()
+ * can be used safely on these kernels.
  */
-#if defined(NV_CHANGE_PAGE_ATTR_PRESENT)
-extern int nv_use_cpa;
-
-#if defined(NVCPU_X86_64) && !defined(KERNEL_2_4) && \
-         (LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 11))
-#define NV_CHANGE_PAGE_ATTR_BUG_PRESENT 1
-#endif
+#if defined(NV_CHANGE_PAGE_ATTR_PRESENT) && defined(NVCPU_X86_64) && \
+  !defined(KERNEL_2_4) && \
+  (LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 11))
+#define NV_CHANGE_PAGE_ATTR_BUG_PRESENT
 #endif
 
 #if defined(NVCPU_X86) || defined(NVCPU_X86_64)
@@ -1123,7 +1127,7 @@
  *
  * We need to be careful to mask out _PAGE_NX when the host system
  * doesn't support this feature or when it's disabled: the kernel
- * may not do this in its implementation of the  change_page_attr()
+ * may not do this in its implementation of the change_page_attr()
  * interface.
  */
 #ifndef X86_FEATURE_NX
diff -ru usr/src/nv/nv-vm.c usr/src/nv.2290218/nv-vm.c
--- usr/src/nv/nv-vm.c	2008-01-22 20:12:23.000000000 -0800
+++ usr/src/nv.2290218/nv-vm.c	2008-03-18 13:15:34.806773619 -0700
@@ -43,42 +43,40 @@
 }
 #endif
 
-/*
- * AMD Athlon processors expose a subtle bug in the Linux
- * kernel, that may lead to AGP memory corruption. Recent
- * kernel versions had a workaround for this problem, but
- * 2.4.20 is the first kernel to address it properly. The
- * page_attr API provides the means to solve the problem. 
- */
-
 static inline void nv_set_page_attrib_uncached(nv_pte_t *page_ptr)
 {
-#if defined(NV_CHANGE_PAGE_ATTR_PRESENT)
-    if (nv_use_cpa)
+    if (nv_update_memory_types)
     {
-        struct page *page = virt_to_page(__va(page_ptr->phys_addr));
+#if defined(NV_SET_PAGES_UC_PRESENT)
+        struct page *page = NV_GET_PAGE_STRUCT(page_ptr->phys_addr);
+        set_pages_uc(page, 1);
+#elif defined(NV_CHANGE_PAGE_ATTR_PRESENT)
+        struct page *page = NV_GET_PAGE_STRUCT(page_ptr->phys_addr);
         pgprot_t prot = PAGE_KERNEL_NOCACHE;
 #if defined(NVCPU_X86) || defined(NVCPU_X86_64)
         pgprot_val(prot) &= __nv_supported_pte_mask;
 #endif
         change_page_attr(page, 1, prot);
-    }
 #endif
+    }
 }
 
 static inline void nv_set_page_attrib_cached(nv_pte_t *page_ptr)
 {
-#if defined(NV_CHANGE_PAGE_ATTR_PRESENT)
-    if (nv_use_cpa)
+    if (nv_update_memory_types)
     {
-        struct page *page = virt_to_page(__va(page_ptr->phys_addr));
+#if defined(NV_SET_PAGES_UC_PRESENT)
+        struct page *page = NV_GET_PAGE_STRUCT(page_ptr->phys_addr);
+        set_pages_wb(page, 1);
+#elif defined(NV_CHANGE_PAGE_ATTR_PRESENT)
+        struct page *page = NV_GET_PAGE_STRUCT(page_ptr->phys_addr);
         pgprot_t prot = PAGE_KERNEL;
 #if defined(NVCPU_X86) || defined(NVCPU_X86_64)
         pgprot_val(prot) &= __nv_supported_pte_mask;
 #endif
         change_page_attr(page, 1, prot);
+#endif
     }
-#endif /* NV_CHANGE_PAGE_ATTR_PRESENT */
 }
 
 static inline void nv_lock_page(nv_pte_t *page_ptr)
@@ -360,8 +358,11 @@
 #if defined(NV_CPA_NEEDS_FLUSHING)
     nv_execute_on_all_cpus(cache_flush, NULL);
 #endif
+#if (defined(NVCPU_X86) || defined(NVCPU_X86_64)) && \
+  defined(NV_CHANGE_PAGE_ATTR_PRESENT)
     global_flush_tlb();
 #endif
+#endif
 }
 
 /*
@@ -656,7 +657,7 @@
 
         address = (unsigned long)virt_addr + i * PAGE_SIZE; 
 
-        pgd = NV_PGD_OFFSET(address, 1, &init_mm);
+        pgd = NV_PGD_OFFSET(address, 1, NULL);
         if (!NV_PGD_PRESENT(pgd))
             goto failed;
 
diff -ru usr/src/nv/nv.c usr/src/nv.2290218/nv.c
--- usr/src/nv/nv.c	2008-01-22 20:12:23.000000000 -0800
+++ usr/src/nv.2290218/nv.c	2008-03-18 13:15:35.950838813 -0700
@@ -112,10 +112,7 @@
 unsigned int nv_remap_limit;
 #endif
 
-#if defined(NV_CHANGE_PAGE_ATTR_PRESENT)
-int nv_use_cpa = 1;
-#endif
-
+int nv_update_memory_types = 1;
 static int nv_mmconfig_failure_detected = 0;
 
 static void *nv_pte_t_cache = NULL;
@@ -919,30 +916,26 @@
 #endif /* defined(NV_BUILD_NV_PAT_SUPPORT) */
 }
 
-
 #if defined(NV_CHANGE_PAGE_ATTR_BUG_PRESENT)
-
-/* nv_verify_cpa_interface - determine if the change_page_attr bug is fixed
- * in this kernel.
+/*
+ * nv_verify_cpa_interface() - determine if the change_page_attr() large page
+ * management accounting bug known to exist in early Linux/x86-64 kernels
+ * is present in this kernel.
  *
- * there's really not a good way to determine if change_page_attr is fixed.
- * we can't really use cpa on 2.6 x86_64 kernels < 2.6.11, as if we run into
- * the accounting bug, the kernel will throw a BUG. this isn't 100% accurate,
- * as it doesn't throw a bug until we try to restore the caching attributes
- * of the page. so if we can track down a 4M allocation, we can mark it
- * uncached and see if the accounting was done correctly.
- * 
- * this is a little ugly, but the most accurate approach to determining if
- * this kernel is good.
+ * There's really no good way to determine if change_page_attr() is working
+ * correctly. We can't reliably use change_page_attr() on Linux/x86-64 2.6
+ * kernels < 2.6.11: if we run into the accounting bug, the Linux kernel will
+ * trigger a BUG() if we attempt to restore the WB memory type of a page
+ * originally part of a large page.
  *
- * why do we even bother? some distributions have back-ported the cpa fix to
- * kernels < 2.6.11. we want to use change_page_attr to avoid random corruption
- * and hangs, but need to make sure it's safe to do so.
+ * So if we can successfully allocate such a page, change its memory type to
+ * UC and check if the accounting was done correctly, we can determine if
+ * the change_page_attr() interface can be used safely.
  *
- * return values:
- *    0 - test passed, interface works
- *    1 - test failed, status unclear
- *   -1 - test failed, interface broken
+ * Return values:
+ *    0 - test passed, the change_page_attr() interface works
+ *    1 - test failed, the status is unclear
+ *   -1 - test failed, the change_page_attr() interface is broken
  */
 
 static inline pte_t *check_large_page(unsigned long vaddr)
@@ -950,7 +943,7 @@
     pgd_t *pgd = NULL;
     pmd_t *pmd = NULL;
 
-    pgd = NV_PGD_OFFSET(vaddr, 1, &init_mm);
+    pgd = NV_PGD_OFFSET(vaddr, 1, NULL);
     if (!NV_PGD_PRESENT(pgd))
         return NULL;
 
@@ -1060,35 +1053,42 @@
 
     return 1;
 }
-
 #endif /* defined(NV_CHANGE_PAGE_ATTR_BUG_PRESENT) */
 
-
-// verify that the kernel's mapping matches the requested type 
-// this is to protect against accidental cache aliasing problems
+/*
+ * nv_verify_page_mappings() - verify that the kernel mapping of the specified
+ * page matches the specified type. This is to help detect bugs in the Linux
+ * kernel's change_page_attr() interface, early.
+ *
+ * This function relies on the ability to perform kernel virtul address to PFN
+ * translations and therefore on 'init_mm'. Unfortunately, the latter is no
+ * longer exported in recent Linux/x86 2.6 kernels. The export was removed at
+ * roughtly the same time as the set_pages_{uc,wb}() change_page_attr()
+ * replacement interfaces were introduced; hopefully, it will be sufficient to
+ * check for their presence.
+ */
 int nv_verify_page_mappings(
     nv_pte_t *page_ptr,
     unsigned int cachetype
 )
 {
-    struct mm_struct *mm;
+#if defined(NV_CHANGE_PAGE_ATTR_PRESENT) || \
+    (defined(NV_SET_PAGES_UC_PRESENT) && !defined(NVCPU_X86))
+    unsigned long retval = -1;
+#if defined(NVCPU_X86) || defined(NVCPU_X86_64)
     pgd_t *pgd = NULL;
     pmd_t *pmd = NULL;
     pte_t *pte = NULL;
-    unsigned long retval = -1;
     unsigned int flags, expected;
     unsigned long address;
     static int count = 0;
 
-#if defined(NV_CHANGE_PAGE_ATTR_PRESENT)
-    if (!nv_use_cpa)
+    if (!nv_update_memory_types)
         return 0;
-#endif
 
     address = (unsigned long)__va(page_ptr->phys_addr);
-    mm = &init_mm; // always a kernel page
 
-    pgd = NV_PGD_OFFSET(address, 1, mm);
+    pgd = NV_PGD_OFFSET(address, 1, NULL);
     if (!NV_PGD_PRESENT(pgd))
     {
         nv_printf(NV_DBG_ERRORS, "NVRM: pgd not present for addr 0x%lx\n", address);
@@ -1154,7 +1154,11 @@
     }
 
 failed:
+#endif /* defined(NVCPU_X86) || defined(NVCPU_X86_64) */
     return retval;
+#else
+    return 0;
+#endif
 }
 
 #if defined(NV_BUILD_NV_PAT_SUPPORT) && defined(CONFIG_HOTPLUG_CPU)
@@ -1200,7 +1204,8 @@
 static int __init nvidia_init_module(void)
 {
     int rc;
-    U032 i, count;
+    U032 i, count, data;
+    nv_state_t *nv = NV_STATE_PTR(&nv_ctl_device);
 
 #if defined(VM_CHECKER)
     nv_init_lock(vm_lock);
@@ -1359,43 +1364,41 @@
     /* create /proc/driver/nvidia */
     nvos_proc_create();
 
-#if defined(NV_CHANGE_PAGE_ATTR_PRESENT)
+    /*
+     * Give users an opportunity to disable the driver's use of
+     * the change_page_attr() and set_pages_{uc,wb}() kernel
+     * interfaces.
+     */
+    rc = rm_read_registry_dword(nv, "NVreg", "UpdateMemoryTypes", &data);
+    if ((rc == 0) && ((int)data != ~0))
     {
-        int data;
-
-        // allow the user to override us with a registry key
-        rc = rm_read_registry_dword(NV_STATE_PTR(&nv_ctl_device), "NVreg", "UseCPA",  &data);
-        if ((rc == 0) && (data != -1))
-        {
-            nv_use_cpa = data;
-        }
+        nv_update_memory_types = data;
+    }
 #if defined(NV_CHANGE_PAGE_ATTR_BUG_PRESENT)
-        else
+    /*
+     * Unless we explicitely detect that the change_page_attr()
+     * inteface is fixed, disable usage of the interface on
+     * this kernel. Notify the user of this problem using the
+     * driver's /proc warnings interface (read by the installer
+     * and the bug report script).
+     */
+    else
+    {
+        rc = nv_verify_cpa_interface();
+        if (rc < 0)
         {
-            /*
-             * Unless we explicitely detect that the change_page_attr()
-             * inteface is fixed, disable usage of the interface on
-             * this kernel. Notify the user of this problem using the
-             * driver's /proc warnings interface (read by the installer
-             * and the bug report script).
-             */
-            rc = nv_verify_cpa_interface();
-            if (rc < 0)
-            {
-                nv_prints(NV_DBG_ERRORS, __cpgattr_warning);
-                nvos_proc_add_warning_file("change_page_attr", __cpgattr_warning);
-                nv_use_cpa = 0;
-            }
-            else if (rc != 0)
-            {
-                nv_prints(NV_DBG_ERRORS, __cpgattr_warning_2);
-                nvos_proc_add_warning_file("change_page_attr", __cpgattr_warning_2);
-                nv_use_cpa = 0;
-            }
+            nv_prints(NV_DBG_ERRORS, __cpgattr_warning);
+            nvos_proc_add_warning_file("change_page_attr", __cpgattr_warning);
+            nv_update_memory_types = 0;
+        }
+        else if (rc != 0)
+        {
+            nv_prints(NV_DBG_ERRORS, __cpgattr_warning_2);
+            nvos_proc_add_warning_file("change_page_attr", __cpgattr_warning_2);
+            nv_update_memory_types = 0;
         }
-#endif
     }
-#endif
+#endif /* defined(NV_CHANGE_PAGE_ATTR_BUG_PRESENT) */
 
 #if defined(NVCPU_X86_64) && defined(CONFIG_IA32_EMULATION) && !defined(HAVE_COMPAT_IOCTL)
     /* Register ioctl conversions for 32 bit clients */
@@ -3230,8 +3233,21 @@
     pte_t *pte = NULL;
     NvU64 retval;
 
-    mm = (kern) ? &init_mm : current->mm;
-    if (!kern) down_read(&current->mm->mmap_sem);
+    if (!kern)
+    {
+        mm = current->mm;
+        down_read(&mm->mmap_sem);
+    }
+    else
+    {
+#if defined(NV_SET_PAGES_UC_PRESENT) && defined(NVCPU_X86)
+        /* nv_printf(NV_DBG_ERRORS,
+            "NVRM: can't translate KVA in nv_get_phys_address()!\n"); */
+        return 0;
+#else
+        mm = NULL;
+#endif
+    }
 
     pgd = NV_PGD_OFFSET(address, kern, mm);
     if (!NV_PGD_PRESENT(pgd))
@@ -3252,22 +3268,24 @@
     retval &= ~_PAGE_NX;
 #endif
 
-    if (!kern) up_read(&current->mm->mmap_sem);
+    if (!kern)
+        up_read(&mm->mmap_sem);
     return retval;
 
 failed:
-    if (!kern) up_read(&current->mm->mmap_sem);
+    if (!kern)
+        up_read(&mm->mmap_sem);
     return 0;
 }
 
 NvU64 NV_API_CALL nv_get_kern_phys_address(NvU64 address)
 {
-    // make sure this address is a kernel pointer
+    /* make sure this address is a kernel virtual address */
 #if defined(DEBUG) && !defined(CONFIG_X86_4G)
     if (address < PAGE_OFFSET)
     {
         nv_printf(NV_DBG_WARNINGS,
-            "NVRM: user address passed to get_kern_phys_address: 0x%lx\n",
+            "NVRM: user address passed to get_kern_phys_address: 0x%llx!\n",
             address);
         return 0;
     }
@@ -3282,12 +3300,12 @@
 
 NvU64 NV_API_CALL nv_get_kern_user_address(NvU64 address)
 {
-    // make sure this address is not a kernel pointer
+    /* make sure this address is not a kernel virtual address */
 #if defined(DEBUG) && !defined(CONFIG_X86_4G)
     if (address >= PAGE_OFFSET)
     {
         nv_printf(NV_DBG_WARNINGS,
-            "NVRM: kernel address passed to get_user_phys_address: 0x%lx\n",
+            "NVRM: kernel address passed to get_user_phys_address: 0x%llx!\n",
             address);
         return 0;
     }
@@ -3989,13 +4007,10 @@
     return -1;
 }
 
-int NV_API_CALL nv_no_incoherent_mappings
-(
-    void
-)
+int NV_API_CALL nv_no_incoherent_mappings(void)
 {
-#if defined(NV_CHANGE_PAGE_ATTR_PRESENT)
-    return 1;
+#if defined(NV_CHANGE_PAGE_ATTR_PRESENT) || defined(NV_SET_PAGES_UC_PRESENT)
+    return (nv_update_memory_types);
 #else
     return 0;
 #endif
diff -ru usr/src/nv/os-interface.c usr/src/nv.2290218/os-interface.c
--- usr/src/nv/os-interface.c	2008-01-22 20:12:23.000000000 -0800
+++ usr/src/nv.2290218/os-interface.c	2008-03-18 13:15:38.098961229 -0700
@@ -1130,6 +1130,18 @@
 {
     void *vaddr;
 
+    if (start == 0)
+    {
+        if (mode != NV_MEMORY_CACHED)
+        {
+            nv_printf(NV_DBG_ERRORS,
+                "NVRM: os_map_kernel_space: won't map address 0x%0llx UC!\n", start);
+            return NULL;
+        }
+        else
+            return (void *)PAGE_OFFSET;
+    }
+
     if (!NV_MAY_SLEEP())
     {
         nv_printf(NV_DBG_ERRORS,
@@ -1162,6 +1174,9 @@
     NvU64 size_bytes
 )
 {
+    if (addr == (void *)PAGE_OFFSET)
+        return;
+
     NV_IOUNMAP(addr, size_bytes);
 }
 
diff -ru usr/src/nv/os-registry.c usr/src/nv.2290218/os-registry.c
--- usr/src/nv/os-registry.c	2008-01-22 20:12:23.000000000 -0800
+++ usr/src/nv.2290218/os-registry.c	2008-03-18 13:15:40.631105529 -0700
@@ -381,34 +381,36 @@
 NV_MODULE_PARAMETER(NVreg_RemapLimit);
 
 /*
- * Option: UseCPA
+ * Option: UpdateMemoryTypes
  *
  * Description:
  *
- * Many kernels have a broken implementation of change_page_attr that leads
- * to cache aliasing problems. x86_64 kernels between 2.6.0 and 2.6.10 will
- * force a kernel BUG_ON() when this condition is encountered. For this
- * reason, the NVIDIA driver is very careful about not using the CPA kernel
- * interface on these kernels.
- *
- * Some distributions have backported this fix to kernel versions that fall
- * within this version range. The NVIDIA driver attempts to automatically
- * detect these fixes and reenable usage of the change_page_attr interface.
- *
- * Due to the serious nature of the problems that can arise from this, the
- * NVIDIA driver implements a manual registry key to force usage of this API
- * to be enabled or disabled. This registry key can be used to force usage
- * of the API on a known fixed kernel if the NVIDIA driver fails to detect
- * the kernel as fixed. This registry key can also be used to disable usage
- * of the API on a bad kernel that is misdetected as a fixed kernel.
- *
- * The default value is '-1' (use NVIDIA driver default logic)
- * A value of '0' will forcibly disable change_page_attr calls.
- * A value of '1' will forcibly enable change_page_attr calls.
+ * Many kernels have broken implementations of the change_page_attr()
+ * kernel interface that may cause cache aliasing problems. Linux/x86-64
+ * kernels between 2.6.0 and 2.6.10 may prompt kernel BUG()s due to
+ * improper accounting in the interface's large page management code, for
+ * example. For this reason, the NVIDIA Linux driver is very careful about
+ * not using the change_page_attr() kernel interface on these kernels.
+ *
+ * Due to the serious nature of the problems that can arise from bugs in
+ * the change_page_attr(), set_pages_{uc,wb}() and other kernel interfaces
+ * used to modify memory types, the NVIDIA driver implements a manual
+ * registry key override to allow forcibly enabling or disabling use of
+ * these APIs.
+ *
+ * Possible values:
+ *
+ * ~0 = use the NVIDIA driver's default logic (default)
+ *  0 = enable use of change_page_attr(), etc.
+ *  1 = disable use of change_page_attr(), etc.
+ *
+ * By default, the NVIDIA driver will attempt to auto-detect if it can
+ * safely use the change_page_attr() and other kernel interfaces to modify
+ * the memory types of kernel mappings.
  */
 
-static int NVreg_UseCPA = -1;
-NV_MODULE_PARAMETER(NVreg_UseCPA);
+static int NVreg_UpdateMemoryTypes = ~0;
+NV_MODULE_PARAMETER(NVreg_UpdateMemoryTypes);
 
 /*
  * Option: DetectPrimaryVga
@@ -511,7 +513,7 @@
     { "NVreg",  "DeviceFileGID",            &NVreg_DeviceFileGID,            1 },
     { "NVreg",  "DeviceFileMode",           &NVreg_DeviceFileMode,           1 },
     { "NVreg",  "RemapLimit",               &NVreg_RemapLimit,               1 },
-    { "NVreg",  "UseCPA",                   &NVreg_UseCPA,                   1 },
+    { "NVreg",  "UpdateMemoryTypes",        &NVreg_UpdateMemoryTypes,        1 },
     { "NVreg",  "DetectPrimaryVga",         &NVreg_DetectPrimaryVga,         1 },
     { "NVreg",  "EnableBrightnessControl",  &NVreg_EnableBrightnessControl,  1 },
     { "NVreg",  "PanelPWMFrequency",        &NVreg_PanelPWMFrequency,        1 },



-- 
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