KVM: arm64: Implement __pkvm_host_share_hyp() using do_share()

__pkvm_host_share_hyp() shares memory between the host and the
hypervisor so implement it as an invocation of the new do_share()
mechanism.

Note that double-sharing is no longer permitted (as this allows us to
reduce the number of page-table walks significantly), but is thankfully
no longer relied upon by the host.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211215161232.1480836-12-qperret@google.com

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index e612fd9..492b993 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -370,94 +370,6 @@ unlock:
        return ret;
 }
 
-static inline bool check_prot(enum kvm_pgtable_prot prot,
-                             enum kvm_pgtable_prot required,
-                             enum kvm_pgtable_prot denied)
-{
-       return (prot & (required | denied)) == required;
-}
-
-int __pkvm_host_share_hyp(u64 pfn)
-{
-       phys_addr_t addr = hyp_pfn_to_phys(pfn);
-       enum kvm_pgtable_prot prot, cur;
-       void *virt = __hyp_va(addr);
-       enum pkvm_page_state state;
-       kvm_pte_t pte;
-       int ret;
-
-       if (!addr_is_memory(addr))
-               return -EINVAL;
-
-       host_lock_component();
-       hyp_lock_component();
-
-       ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, NULL);
-       if (ret)
-               goto unlock;
-       if (!pte)
-               goto map_shared;
-
-       /*
-        * Check attributes in the host stage-2 PTE. We need the page to be:
-        *  - mapped RWX as we're sharing memory;
-        *  - not borrowed, as that implies absence of ownership.
-        * Otherwise, we can't let it got through
-        */
-       cur = kvm_pgtable_stage2_pte_prot(pte);
-       prot = pkvm_mkstate(0, PKVM_PAGE_SHARED_BORROWED);
-       if (!check_prot(cur, PKVM_HOST_MEM_PROT, prot)) {
-               ret = -EPERM;
-               goto unlock;
-       }
-
-       state = pkvm_getstate(cur);
-       if (state == PKVM_PAGE_OWNED)
-               goto map_shared;
-
-       /*
-        * Tolerate double-sharing the same page, but this requires
-        * cross-checking the hypervisor stage-1.
-        */
-       if (state != PKVM_PAGE_SHARED_OWNED) {
-               ret = -EPERM;
-               goto unlock;
-       }
-
-       ret = kvm_pgtable_get_leaf(&pkvm_pgtable, (u64)virt, &pte, NULL);
-       if (ret)
-               goto unlock;
-
-       /*
-        * If the page has been shared with the hypervisor, it must be
-        * already mapped as SHARED_BORROWED in its stage-1.
-        */
-       cur = kvm_pgtable_hyp_pte_prot(pte);
-       prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
-       if (!check_prot(cur, prot, ~prot))
-               ret = -EPERM;
-       goto unlock;
-
-map_shared:
-       /*
-        * If the page is not yet shared, adjust mappings in both page-tables
-        * while both locks are held.
-        */
-       prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
-       ret = pkvm_create_mappings_locked(virt, virt + PAGE_SIZE, prot);
-       BUG_ON(ret);
-
-       prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_OWNED);
-       ret = host_stage2_idmap_locked(addr, PAGE_SIZE, prot);
-       BUG_ON(ret);
-
-unlock:
-       hyp_unlock_component();
-       host_unlock_component();
-
-       return ret;
-}
-
 void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
 {
        struct kvm_vcpu_fault_info fault;
@@ -708,3 +620,36 @@ static int do_share(struct pkvm_mem_share *share)
 
        return WARN_ON(__do_share(share));
 }
+
+int __pkvm_host_share_hyp(u64 pfn)
+{
+       int ret;
+       u64 host_addr = hyp_pfn_to_phys(pfn);
+       u64 hyp_addr = (u64)__hyp_va(host_addr);
+       struct pkvm_mem_share share = {
+               .tx     = {
+                       .nr_pages       = 1,
+                       .initiator      = {
+                               .id     = PKVM_ID_HOST,
+                               .addr   = host_addr,
+                               .host   = {
+                                       .completer_addr = hyp_addr,
+                               },
+                       },
+                       .completer      = {
+                               .id     = PKVM_ID_HYP,
+                       },
+               },
+               .completer_prot = PAGE_HYP,
+       };
+
+       host_lock_component();
+       hyp_lock_component();
+
+       ret = do_share(&share);
+
+       hyp_unlock_component();
+       host_unlock_component();
+
+       return ret;
+}