[RFC PATCH v2 08/19] KVM: x86: Extend kvm_vm_set_mem_attributes() with a mask

[Mickaël Salaün <mic@xxxxxxxxxxx>]

Enable to only update a subset of attributes.

This is needed to be able to use the XArray for different use cases and
make sure they don't interfere (see a following commit).

Cc: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Madhavan T. Venkataraman <madvenka@xxxxxxxxxxxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>
---

Changes since v1:
* New patch
---
 arch/x86/kvm/mmu/mmu.c   |  2 +-
 include/linux/kvm_host.h |  2 +-
 virt/kvm/kvm_main.c      | 27 +++++++++++++++++++--------
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4d378d308762..d7010e09440d 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7283,7 +7283,7 @@ static bool hugepage_has_attrs(struct kvm *kvm, struct 
kvm_memory_slot *slot,
 
        for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
                if (hugepage_test_mixed(slot, gfn, level - 1) ||
-                   attrs != kvm_get_memory_attributes(kvm, gfn))
+                   !(attrs & kvm_get_memory_attributes(kvm, gfn)))
                        return false;
        }
        return true;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 85b8648fd892..de68390ab0f2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2397,7 +2397,7 @@ bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
 bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
                                         struct kvm_gfn_range *range);
 int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
-                             unsigned long attributes);
+                             unsigned long attributes, unsigned long mask);
 
 static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
 {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 0096ccfbb609..e2c178db17d5 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2436,7 +2436,7 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
 #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
 /*
  * Returns true if _all_ gfns in the range [@start, @end) have attributes
- * matching @attrs.
+ * matching the @attrs bitmask.
  */
 bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
                                     unsigned long attrs)
@@ -2459,7 +2459,8 @@ bool kvm_range_has_memory_attributes(struct kvm *kvm, 
gfn_t start, gfn_t end,
                        entry = xas_next(&xas);
                } while (xas_retry(&xas, entry));
 
-               if (xas.xa_index != index || xa_to_value(entry) != attrs) {
+               if (xas.xa_index != index ||
+                   (xa_to_value(entry) & attrs) != attrs) {
                        has_attrs = false;
                        break;
                }
@@ -2553,7 +2554,7 @@ static bool kvm_pre_set_memory_attributes(struct kvm *kvm,
 
 /* Set @attributes for the gfn range [@start, @end). */
 int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
-                                    unsigned long attributes)
+                             unsigned long attributes, unsigned long mask)
 {
        struct kvm_mmu_notifier_range pre_set_range = {
                .start = start,
@@ -2572,11 +2573,8 @@ int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t 
start, gfn_t end,
                .may_block = true,
        };
        unsigned long i;
-       void *entry;
        int r = 0;
 
-       entry = attributes ? xa_mk_value(attributes) : NULL;
-
        lockdep_assert_held(&kvm->slots_arch_lock);
 
        /* Nothing to do if the entire range as the desired attributes. */
@@ -2596,6 +2594,16 @@ int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t 
start, gfn_t end,
        kvm_handle_gfn_range(kvm, &pre_set_range);
 
        for (i = start; i < end; i++) {
+               unsigned long value = 0;
+               void *entry;
+
+               entry = xa_load(&kvm->mem_attr_array, i);
+               if (xa_is_value(entry))
+                       value = xa_to_value(entry) & ~mask;
+
+               value |= attributes & mask;
+               entry = value ? xa_mk_value(value) : NULL;
+
                r = xa_err(xa_store(&kvm->mem_attr_array, i, entry,
                                    GFP_KERNEL_ACCOUNT));
                KVM_BUG_ON(r, kvm);
@@ -2609,12 +2617,14 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm 
*kvm,
                                           struct kvm_memory_attributes *attrs)
 {
        int r;
+       unsigned long attrs_mask;
        gfn_t start, end;
 
        /* flags is currently not used. */
        if (attrs->flags)
                return -EINVAL;
-       if (attrs->attributes & ~kvm_supported_mem_attributes(kvm))
+       attrs_mask = kvm_supported_mem_attributes(kvm);
+       if (attrs->attributes & ~attrs_mask)
                return -EINVAL;
        if (attrs->size == 0 || attrs->address + attrs->size < attrs->address)
                return -EINVAL;
@@ -2632,7 +2642,8 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm 
*kvm,
        BUILD_BUG_ON(sizeof(attrs->attributes) != sizeof(unsigned long));
 
        mutex_lock(&kvm->slots_arch_lock);
-       r = kvm_vm_set_mem_attributes(kvm, start, end, attrs->attributes);
+       r = kvm_vm_set_mem_attributes(kvm, start, end, attrs->attributes,
+                                     attrs_mask);
        mutex_unlock(&kvm->slots_arch_lock);
        return r;
 }
-- 
2.42.1