drm/i915/gtt: Add read only pages to gen8_pte_encode

commit 25dda4dabeeb12af5209b0183c788ef2a88dabbe upstream.

We can set a bit inside the ppGTT PTE to indicate a page is read-only;
writes from the GPU will be discarded. We can use this to protect pages
and in particular support read-only userptr mappings (necessary for
importing PROT_READ vma).

Signed-off-by: Jon Bloomfield <jon.bloomfield@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180712185315.3288-1-chris@chris-wilson.co.uk
Reviewed-by: Jon Bloomfield <jon.bloomfield@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 0bb4232f66bcac1ad9653c073c1cbe7cb7375c16..088f9c03cbb45cbd747728d24f16b58898d7b94d 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -197,11 +197,14 @@ static void ppgtt_unbind_vma(struct i915_vma *vma)
 
 static gen8_pte_t gen8_pte_encode(dma_addr_t addr,
                                  enum i915_cache_level level,
-                                 bool valid)
+                                 bool valid, u32 flags)
 {
        gen8_pte_t pte = valid ? _PAGE_PRESENT | _PAGE_RW : 0;
        pte |= addr;
 
+       if (unlikely(flags & PTE_READ_ONLY))
+               pte &= ~_PAGE_RW;
+
        switch (level) {
        case I915_CACHE_NONE:
                pte |= PPAT_UNCACHED_INDEX;
@@ -472,7 +475,7 @@ static void gen8_initialize_pt(struct i915_address_space *vm,
        gen8_pte_t scratch_pte;
 
        scratch_pte = gen8_pte_encode(vm->scratch_page.daddr,
-                                     I915_CACHE_LLC, true);
+                                     I915_CACHE_LLC, true, 0);
 
        fill_px(vm->dev, pt, scratch_pte);
 }
@@ -769,7 +772,7 @@ static void gen8_ppgtt_clear_range(struct i915_address_space *vm,
 {
        struct i915_hw_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
        gen8_pte_t scratch_pte = gen8_pte_encode(vm->scratch_page.daddr,
-                                                I915_CACHE_LLC, use_scratch);
+                                                I915_CACHE_LLC, use_scratch, 0);
 
        if (!USES_FULL_48BIT_PPGTT(vm->dev)) {
                gen8_ppgtt_clear_pte_range(vm, &ppgtt->pdp, start, length,
@@ -809,7 +812,7 @@ gen8_ppgtt_insert_pte_entries(struct i915_address_space *vm,
 
                pt_vaddr[pte] =
                        gen8_pte_encode(sg_page_iter_dma_address(sg_iter),
-                                       cache_level, true);
+                                       cache_level, true, 0);
                if (++pte == GEN8_PTES) {
                        kunmap_px(ppgtt, pt_vaddr);
                        pt_vaddr = NULL;
@@ -1452,7 +1455,7 @@ static void gen8_dump_ppgtt(struct i915_hw_ppgtt *ppgtt, struct seq_file *m)
        uint64_t start = ppgtt->base.start;
        uint64_t length = ppgtt->base.total;
        gen8_pte_t scratch_pte = gen8_pte_encode(vm->scratch_page.daddr,
-                                                I915_CACHE_LLC, true);
+                                                I915_CACHE_LLC, true, 0);
 
        if (!USES_FULL_48BIT_PPGTT(vm->dev)) {
                gen8_dump_pdp(&ppgtt->pdp, start, length, scratch_pte, m);
@@ -2321,7 +2324,7 @@ static void gen8_ggtt_insert_page(struct i915_address_space *vm,
 
        rpm_atomic_seq = assert_rpm_atomic_begin(dev_priv);
 
-       gen8_set_pte(pte, gen8_pte_encode(addr, level, true));
+       gen8_set_pte(pte, gen8_pte_encode(addr, level, true, 0));
 
        I915_WRITE(GFX_FLSH_CNTL_GEN6, GFX_FLSH_CNTL_EN);
        POSTING_READ(GFX_FLSH_CNTL_GEN6);
@@ -2348,7 +2351,7 @@ static void gen8_ggtt_insert_entries(struct i915_address_space *vm,
        gtt_entries = (gen8_pte_t __iomem *)ggtt->gsm + (start >> PAGE_SHIFT);
 
        for_each_sgt_dma(addr, sgt_iter, st) {
-               gtt_entry = gen8_pte_encode(addr, level, true);
+               gtt_entry = gen8_pte_encode(addr, level, true, 0);
                gen8_set_pte(&gtt_entries[i++], gtt_entry);
        }
 
@@ -2499,7 +2502,7 @@ static void gen8_ggtt_clear_range(struct i915_address_space *vm,
 
        scratch_pte = gen8_pte_encode(vm->scratch_page.daddr,
                                      I915_CACHE_LLC,
-                                     use_scratch);
+                                     use_scratch, 0);
        for (i = 0; i < num_entries; i++)
                gen8_set_pte(&gtt_base[i], scratch_pte);
        readl(gtt_base);