KVM: arm64: Restrict the scope of the 'writable' attribute

The 'writable' field is ambiguous, and indicates multiple things:

- whether the underlying memslot is writable

- whether we are resolving the fault with writable attributes

Add a new field to kvm_s2_fault_vma_info (map_writable) to indicate
the former condition, and have local writable variables to track
the latter.

Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 227bc34bc535ea57306d380aaa2eed8922d67bdc..f8e88539988cbd607b55e8549031e9b83bdd85ba 100644 (file)
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1653,6 +1653,7 @@ struct kvm_s2_fault_vma_info {
        gfn_t           gfn;
        bool            mte_allowed;
        bool            is_vma_cacheable;
+       bool            map_writable;
 };
 
 static short kvm_s2_resolve_vma_size(const struct kvm_s2_fault_desc *s2fd,
@@ -1718,7 +1719,6 @@ static short kvm_s2_resolve_vma_size(const struct kvm_s2_fault_desc *s2fd,
 }
 
 struct kvm_s2_fault {
-       bool writable;
        bool s2_force_noncacheable;
        kvm_pfn_t pfn;
        bool force_pte;
@@ -1799,7 +1799,7 @@ static int kvm_s2_fault_pin_pfn(const struct kvm_s2_fault_desc *s2fd,
 
        fault->pfn = __kvm_faultin_pfn(s2fd->memslot, get_canonical_gfn(s2fd, s2vi),
                                       kvm_is_write_fault(s2fd->vcpu) ? FOLL_WRITE : 0,
-                                      &fault->writable, &fault->page);
+                                      &s2vi->map_writable, &fault->page);
        if (unlikely(is_error_noslot_pfn(fault->pfn))) {
                if (fault->pfn == KVM_PFN_ERR_HWPOISON) {
                        kvm_send_hwpoison_signal(s2fd->hva, __ffs(s2vi->vma_pagesize));
@@ -1816,6 +1816,7 @@ static int kvm_s2_fault_compute_prot(const struct kvm_s2_fault_desc *s2fd,
                                     const struct kvm_s2_fault_vma_info *s2vi)
 {
        struct kvm *kvm = s2fd->vcpu->kvm;
+       bool writable = s2vi->map_writable;
 
        /*
         * Check if this is non-struct page memory PFN, and cannot support
@@ -1855,7 +1856,7 @@ static int kvm_s2_fault_compute_prot(const struct kvm_s2_fault_desc *s2fd,
                 * Only actually map the page as writable if this was a write
                 * fault.
                 */
-               fault->writable = false;
+               writable = false;
        }
 
        if (kvm_vcpu_trap_is_exec_fault(s2fd->vcpu) && fault->s2_force_noncacheable)
@@ -1873,9 +1874,9 @@ static int kvm_s2_fault_compute_prot(const struct kvm_s2_fault_desc *s2fd,
        }
 
        if (s2fd->nested)
-               adjust_nested_fault_perms(s2fd->nested, &fault->prot, &fault->writable);
+               adjust_nested_fault_perms(s2fd->nested, &fault->prot, &writable);
 
-       if (fault->writable)
+       if (writable)
                fault->prot |= KVM_PGTABLE_PROT_W;
 
        if (kvm_vcpu_trap_is_exec_fault(s2fd->vcpu))
@@ -1904,6 +1905,7 @@ static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd,
                            const struct kvm_s2_fault_vma_info *s2vi, void *memcache)
 {
        enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_SHARED;
+       bool writable = fault->prot & KVM_PGTABLE_PROT_W;
        struct kvm *kvm = s2fd->vcpu->kvm;
        struct kvm_pgtable *pgt;
        long perm_fault_granule;
@@ -1964,7 +1966,7 @@ static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd,
        }
 
 out_unlock:
-       kvm_release_faultin_page(kvm, fault->page, !!ret, fault->writable);
+       kvm_release_faultin_page(kvm, fault->page, !!ret, writable);
        kvm_fault_unlock(kvm);
 
        /*
@@ -1972,7 +1974,7 @@ out_unlock:
         * making sure we adjust the canonical IPA if the mapping size has
         * been updated (via a THP upgrade, for example).
         */
-       if (fault->writable && !ret) {
+       if (writable && !ret) {
                phys_addr_t ipa = gfn_to_gpa(get_canonical_gfn(s2fd, s2vi));
                ipa &= ~(mapping_size - 1);
                mark_page_dirty_in_slot(kvm, s2fd->memslot, gpa_to_gfn(ipa));