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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Quentin, On Mon, Aug 9, 2021 at 5:25 PM Quentin Perret wrote: > > As the hypervisor maps the host's .bss and .rodata sections in its > stage-1, make sure to tag them as shared in hyp and host page-tables. > > But since the hypervisor relies on the presence of these mappings, we > cannot let the host in complete control of the memory regions -- it > must not unshare or donate them to another entity for example. To > prevent this, let's transfer the ownership of those ranges to the > hypervisor itself, and share the pages back with the host. > > Signed-off-by: Quentin Perret > --- Reviewed-by: Fuad Tabba Thanks, /fuad > arch/arm64/kvm/hyp/nvhe/setup.c | 82 +++++++++++++++++++++++++++++---- > 1 file changed, 74 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c > index 0b574d106519..57c27846320f 100644 > --- a/arch/arm64/kvm/hyp/nvhe/setup.c > +++ b/arch/arm64/kvm/hyp/nvhe/setup.c > @@ -58,6 +58,7 @@ static int recreate_hyp_mappings(phys_addr_t phys, unsigned long size, > { > void *start, *end, *virt = hyp_phys_to_virt(phys); > unsigned long pgt_size = hyp_s1_pgtable_pages() << PAGE_SHIFT; > + enum kvm_pgtable_prot prot; > int ret, i; > > /* Recreate the hyp page-table using the early page allocator */ > @@ -83,10 +84,6 @@ static int recreate_hyp_mappings(phys_addr_t phys, unsigned long size, > if (ret) > return ret; > > - ret = pkvm_create_mappings(__start_rodata, __end_rodata, PAGE_HYP_RO); > - if (ret) > - return ret; > - > ret = pkvm_create_mappings(__hyp_rodata_start, __hyp_rodata_end, PAGE_HYP_RO); > if (ret) > return ret; > @@ -95,10 +92,6 @@ static int recreate_hyp_mappings(phys_addr_t phys, unsigned long size, > if (ret) > return ret; > > - ret = pkvm_create_mappings(__hyp_bss_end, __bss_stop, PAGE_HYP_RO); > - if (ret) > - return ret; > - > ret = pkvm_create_mappings(virt, virt + size, PAGE_HYP); > if (ret) > return ret; > @@ -117,6 +110,24 @@ static int recreate_hyp_mappings(phys_addr_t phys, unsigned long size, > return ret; > } > > + /* > + * Map the host's .bss and .rodata sections RO in the hypervisor, but > + * transfer the ownership from the host to the hypervisor itself to > + * make sure it can't be donated or shared with another entity. > + * > + * The ownership transition requires matching changes in the host > + * stage-2. This will be done later (see finalize_host_mappings()) once > + * the hyp_vmemmap is addressable. > + */ > + prot = pkvm_mkstate(PAGE_HYP_RO, PKVM_PAGE_SHARED_OWNED); > + ret = pkvm_create_mappings(__start_rodata, __end_rodata, prot); > + if (ret) > + return ret; > + > + ret = pkvm_create_mappings(__hyp_bss_end, __bss_stop, prot); > + if (ret) > + return ret; > + > return 0; > } > > @@ -148,6 +159,57 @@ static void hpool_put_page(void *addr) > hyp_put_page(&hpool, addr); > } > > +static int finalize_host_mappings_walker(u64 addr, u64 end, u32 level, > + kvm_pte_t *ptep, > + enum kvm_pgtable_walk_flags flag, > + void * const arg) > +{ > + enum kvm_pgtable_prot prot; > + enum pkvm_page_state state; > + kvm_pte_t pte = *ptep; > + phys_addr_t phys; > + > + if (!kvm_pte_valid(pte)) > + return 0; > + > + if (level != (KVM_PGTABLE_MAX_LEVELS - 1)) > + return -EINVAL; > + > + phys = kvm_pte_to_phys(pte); > + if (!addr_is_memory(phys)) > + return 0; > + > + /* > + * Adjust the host stage-2 mappings to match the ownership attributes > + * configured in the hypervisor stage-1. > + */ > + state = pkvm_getstate(kvm_pgtable_hyp_pte_prot(pte)); > + switch (state) { > + case PKVM_PAGE_OWNED: > + return host_stage2_set_owner_locked(phys, PAGE_SIZE, pkvm_hyp_id); > + case PKVM_PAGE_SHARED_OWNED: > + prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_BORROWED); > + break; > + case PKVM_PAGE_SHARED_BORROWED: > + prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_OWNED); > + break; > + default: > + return -EINVAL; > + } > + > + return host_stage2_idmap_locked(phys, PAGE_SIZE, prot); > +} > + > +static int finalize_host_mappings(void) > +{ > + struct kvm_pgtable_walker walker = { > + .cb = finalize_host_mappings_walker, > + .flags = KVM_PGTABLE_WALK_LEAF, > + }; > + > + return kvm_pgtable_walk(&pkvm_pgtable, 0, BIT(pkvm_pgtable.ia_bits), &walker); > +} > + > void __noreturn __pkvm_init_finalise(void) > { > struct kvm_host_data *host_data = this_cpu_ptr(&kvm_host_data); > @@ -167,6 +229,10 @@ void __noreturn __pkvm_init_finalise(void) > if (ret) > goto out; > > + ret = finalize_host_mappings(); > + if (ret) > + goto out; > + > pkvm_pgtable_mm_ops = (struct kvm_pgtable_mm_ops) { > .zalloc_page = hyp_zalloc_hyp_page, > .phys_to_virt = hyp_phys_to_virt, > -- > 2.32.0.605.g8dce9f2422-goog > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel