Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 mm tree changes from Ingo Molnar:
 "The biggest change is full PAT support from Jürgen Gross:

     The x86 architecture offers via the PAT (Page Attribute Table) a
     way to specify different caching modes in page table entries.  The
     PAT MSR contains 8 entries each specifying one of 6 possible cache
     modes.  A pte references one of those entries via 3 bits:
     _PAGE_PAT, _PAGE_PWT and _PAGE_PCD.

     The Linux kernel currently supports only 4 different cache modes.
     The PAT MSR is set up in a way that the setting of _PAGE_PAT in a
     pte doesn't matter: the top 4 entries in the PAT MSR are the same
     as the 4 lower entries.

     This results in the kernel not supporting e.g. write-through mode.
     Especially this cache mode would speed up drivers of video cards
     which now have to use uncached accesses.

     OTOH some old processors (Pentium) don't support PAT correctly and
     the Xen hypervisor has been using a different PAT MSR configuration
     for some time now and can't change that as this setting is part of
     the ABI.

     This patch set abstracts the cache mode from the pte and introduces
     tables to translate between cache mode and pte bits (the default
     cache mode "write back" is hard-wired to PAT entry 0).  The tables
     are statically initialized with values being compatible to old
     processors and current usage.  As soon as the PAT MSR is changed
     (or - in case of Xen - is read at boot time) the tables are changed
     accordingly.  Requests of mappings with special cache modes are
     always possible now, in case they are not supported there will be a
     fallback to a compatible but slower mode.

     Summing it up, this patch set adds the following features:

      - capability to support WT and WP cache modes on processors with
        full PAT support

      - processors with no or uncorrect PAT support are still working as
        today, even if WT or WP cache mode are selected by drivers for
        some pages

      - reduction of Xen special handling regarding cache mode

  Another change is a boot speedup on ridiculously large RAM systems,
  plus other smaller fixes"

* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
  x86: mm: Move PAT only functions to mm/pat.c
  xen: Support Xen pv-domains using PAT
  x86: Enable PAT to use cache mode translation tables
  x86: Respect PAT bit when copying pte values between large and normal pages
  x86: Support PAT bit in pagetable dump for lower levels
  x86: Clean up pgtable_types.h
  x86: Use new cache mode type in memtype related functions
  x86: Use new cache mode type in mm/ioremap.c
  x86: Use new cache mode type in setting page attributes
  x86: Remove looking for setting of _PAGE_PAT_LARGE in pageattr.c
  x86: Use new cache mode type in track_pfn_remap() and track_pfn_insert()
  x86: Use new cache mode type in mm/iomap_32.c
  x86: Use new cache mode type in asm/pgtable.h
  x86: Use new cache mode type in arch/x86/mm/init_64.c
  x86: Use new cache mode type in arch/x86/pci
  x86: Use new cache mode type in drivers/video/fbdev/vermilion
  x86: Use new cache mode type in drivers/video/fbdev/gbefb.c
  x86: Use new cache mode type in include/asm/fb.h
  x86: Make page cache mode a real type
  x86: mm: Use 2GB memory block size on large-memory x86-64 systems
  ...

3 files changed, 8 insertions, 65 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index fac5e4f9607c..6bf3a13e3e0f 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1100,12 +1100,6 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
                 /* Fast syscall setup is all done in hypercalls, so
                    these are all ignored.  Stub them out here to stop
                    Xen console noise. */
-                break;
-
-        case MSR_IA32_CR_PAT:
-                if (smp_processor_id() == 0)
-                        xen_set_pat(((u64)high << 32) | low);
-                break;
 
         default:
                 ret = native_write_msr_safe(msr, low, high);
@@ -1561,10 +1555,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
         /* Prevent unwanted bits from being set in PTEs. */
         __supported_pte_mask &= ~_PAGE_GLOBAL;
-#if 0
-        if (!xen_initial_domain())
-#endif
-                __supported_pte_mask &= ~(_PAGE_PWT | _PAGE_PCD);
 
         /*
          * Prevent page tables from being allocated in highmem, even
@@ -1618,14 +1608,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
          */
         acpi_numa = -1;
 #endif
-#ifdef CONFIG_X86_PAT
-        /*
-         * For right now disable the PAT. We should remove this once
-         * git commit 8eaffa67b43e99ae581622c5133e20b0f48bcef1
-         * (xen/pat: Disable PAT support for now) is reverted.
-         */
-        pat_enabled = 0;
-#endif
         /* Don't do the full vcpu_info placement stuff until we have a
            possible map and a non-dummy shared_info. */
         per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
@@ -1636,6 +1618,13 @@ asmlinkage __visible void __init xen_start_kernel(void)
         xen_raw_console_write("mapping kernel into physical memory\n");
         xen_setup_kernel_pagetable((pgd_t *)xen_start_info->pt_base, xen_start_info->nr_pages);
 
+        /*
+         * Modify the cache mode translation tables to match Xen's PAT
+         * configuration.
+         */
+
+        pat_init_cache_modes();
+
         /* keep using Xen gdt for now; no urgent need to change it */
 
 #ifdef CONFIG_X86_32
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index a8a1a3d08d4d..9855eb8ee4b3 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -410,13 +410,7 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
 __visible pteval_t xen_pte_val(pte_t pte)
 {
         pteval_t pteval = pte.pte;
-#if 0
-        /* If this is a WC pte, convert back from Xen WC to Linux WC */
-        if ((pteval & (_PAGE_PAT | _PAGE_PCD | _PAGE_PWT)) == _PAGE_PAT) {
-                WARN_ON(!pat_enabled);
-                pteval = (pteval & ~_PAGE_PAT) | _PAGE_PWT;
-        }
-#endif
+
         return pte_mfn_to_pfn(pteval);
 }
 PV_CALLEE_SAVE_REGS_THUNK(xen_pte_val);
@@ -427,47 +421,8 @@ __visible pgdval_t xen_pgd_val(pgd_t pgd)
 }
 PV_CALLEE_SAVE_REGS_THUNK(xen_pgd_val);
 
-/*
- * Xen's PAT setup is part of its ABI, though I assume entries 6 & 7
- * are reserved for now, to correspond to the Intel-reserved PAT
- * types.
- *
- * We expect Linux's PAT set as follows:
- *
- * Idx  PTE flags        Linux    Xen    Default
- * 0                     WB       WB     WB
- * 1            PWT      WC       WT     WT
- * 2        PCD          UC-      UC-    UC-
- * 3        PCD PWT      UC       UC     UC
- * 4    PAT              WB       WC     WB
- * 5    PAT     PWT      WC       WP     WT
- * 6    PAT PCD          UC-      rsv    UC-
- * 7    PAT PCD PWT      UC       rsv    UC
- */
-
-void xen_set_pat(u64 pat)
-{
-        /* We expect Linux to use a PAT setting of
-         * UC UC- WC WB (ignoring the PAT flag) */
-        WARN_ON(pat != 0x0007010600070106ull);
-}
-
 __visible pte_t xen_make_pte(pteval_t pte)
 {
-#if 0
-        /* If Linux is trying to set a WC pte, then map to the Xen WC.
-         * If _PAGE_PAT is set, then it probably means it is really
-         * _PAGE_PSE, so avoid fiddling with the PAT mapping and hope
-         * things work out OK...
-         *
-         * (We should never see kernel mappings with _PAGE_PSE set,
-         * but we could see hugetlbfs mappings, I think.).
-         */
-        if (pat_enabled && !WARN_ON(pte & _PAGE_PAT)) {
-                if ((pte & (_PAGE_PCD | _PAGE_PWT)) == _PAGE_PWT)
-                        pte = (pte & ~(_PAGE_PCD | _PAGE_PWT)) | _PAGE_PAT;
-        }
-#endif
         pte = pte_pfn_to_mfn(pte);
 
         return native_make_pte(pte);
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 28c7e0be56e4..4ab9298c5e17 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -33,7 +33,6 @@ extern unsigned long xen_max_p2m_pfn;
 
 void xen_mm_pin_all(void);
 void xen_mm_unpin_all(void);
-void xen_set_pat(u64);
 
 char * __init xen_memory_setup(void);
 char * xen_auto_xlated_memory_setup(void);