From 8499e08c40e1466528bc443f75e594b09bfc469b Mon Sep 17 00:00:00 2001 From: Quentin Perret Date: Tue, 26 Oct 2021 13:43:08 +0100 Subject: [PATCH] ANDROID: KVM: arm64: Add helpers to pin memory shared with hyp Add helpers allowing the hypervisor to check whether a range of pages are currently shared by the host, and 'pin' them if so by blocking host unshare operations until the memory has been unpinned. This will allow the hypervisor to take references on host-provided data-structures (struct kvm and such) and be guaranteed these pages will remain in a stable state until it decides to release them, e.g. during guest teardown. Signed-off-by: Quentin Perret Bug: 209580772 Change-Id: I60ff204bd11e78e3e2ce21defc0d94ae916f5097 Signed-off-by: Will Deacon --- arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 3 ++ arch/arm64/kvm/hyp/include/nvhe/memory.h | 7 ++- arch/arm64/kvm/hyp/nvhe/mem_protect.c | 48 +++++++++++++++++++ 3 files changed, 57 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h index c1cea5a5dbc4..0e2e175486a0 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h @@ -65,6 +65,9 @@ int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id); int kvm_host_prepare_stage2(void *pgt_pool_base); void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt); +int hyp_pin_shared_mem(void *from, void *to); +void hyp_unpin_shared_mem(void *from, void *to); + static __always_inline void __load_host_stage2(void) { if (static_branch_likely(&kvm_protected_mode_initialized)) diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h index 418b66a82a50..e8a78b72aabf 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h @@ -51,10 +51,15 @@ static inline void hyp_page_ref_inc(struct hyp_page *p) p->refcount++; } -static inline int hyp_page_ref_dec_and_test(struct hyp_page *p) +static inline void hyp_page_ref_dec(struct hyp_page *p) { BUG_ON(!p->refcount); p->refcount--; +} + +static inline int hyp_page_ref_dec_and_test(struct hyp_page *p) +{ + hyp_page_ref_dec(p); return (p->refcount == 0); } diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 4b7a5cc58418..52e909db1eff 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -688,6 +688,9 @@ static int hyp_ack_unshare(u64 addr, const struct pkvm_mem_transition *tx) { u64 size = tx->nr_pages * PAGE_SIZE; + if (tx->initiator.id == PKVM_ID_HOST && hyp_page_count((void *)addr)) + return -EBUSY; + if (__hyp_ack_skip_pgtable_check(tx)) return 0; @@ -1101,3 +1104,48 @@ int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages) return ret; } + +int hyp_pin_shared_mem(void *from, void *to) +{ + u64 cur, start = ALIGN_DOWN((u64)from, PAGE_SIZE); + u64 end = PAGE_ALIGN((u64)to); + u64 size = end - start; + int ret; + + host_lock_component(); + hyp_lock_component(); + + ret = __host_check_page_state_range(__hyp_pa(start), size, + PKVM_PAGE_SHARED_OWNED); + if (ret) + goto unlock; + + ret = __hyp_check_page_state_range(start, size, + PKVM_PAGE_SHARED_BORROWED); + if (ret) + goto unlock; + + for (cur = start; cur < end; cur += PAGE_SIZE) + hyp_page_ref_inc(hyp_virt_to_page(cur)); + +unlock: + hyp_unlock_component(); + host_unlock_component(); + + return ret; +} + +void hyp_unpin_shared_mem(void *from, void *to) +{ + u64 cur, start = ALIGN_DOWN((u64)from, PAGE_SIZE); + u64 end = PAGE_ALIGN((u64)to); + + host_lock_component(); + hyp_lock_component(); + + for (cur = start; cur < end; cur += PAGE_SIZE) + hyp_page_ref_dec(hyp_virt_to_page(cur)); + + hyp_unlock_component(); + host_unlock_component(); +}