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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 The host kernel is currently able to change EL2 stage-1 mappings without restrictions thanks to the __pkvm_create_mappings() hypercall. But in a world where the host is no longer part of the TCB, this clearly poses a problem. To fix this, introduce a new hypercall to allow the host to share a physical memory page with the hypervisor, and remove the __pkvm_create_mappings() variant. The new hypercall implements ownership and permission checks before allowing the sharing operation, and it annotates the shared page in the hypervisor stage-1 and host stage-2 page-tables. Signed-off-by: Quentin Perret --- arch/arm64/include/asm/kvm_asm.h | 2 +- arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 1 + arch/arm64/kvm/hyp/nvhe/hyp-main.c | 11 +-- arch/arm64/kvm/hyp/nvhe/mem_protect.c | 90 +++++++++++++++++++ arch/arm64/kvm/mmu.c | 28 +++++- 5 files changed, 120 insertions(+), 12 deletions(-) diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index 9f0bf2109be7..78db818ae2c9 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -59,7 +59,7 @@ #define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs 13 #define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs 14 #define __KVM_HOST_SMCCC_FUNC___pkvm_init 15 -#define __KVM_HOST_SMCCC_FUNC___pkvm_create_mappings 16 +#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp 16 #define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping 17 #define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector 18 #define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 19 diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h index 8e5725d032b2..1b8e59a9d065 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h @@ -49,6 +49,7 @@ extern struct host_kvm host_kvm; int __pkvm_prot_finalize(void); int __pkvm_mark_hyp(phys_addr_t start, phys_addr_t end); +int __pkvm_host_share_hyp(u64 pfn); int host_stage2_idmap_locked(u64 start, u64 end, enum kvm_pgtable_prot prot); int kvm_host_prepare_stage2(void *pgt_pool_base); diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index 1632f001f4ed..dd155646ec86 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -140,14 +140,11 @@ static void handle___pkvm_cpu_set_vector(struct kvm_cpu_context *host_ctxt) cpu_reg(host_ctxt, 1) = pkvm_cpu_set_vector(slot); } -static void handle___pkvm_create_mappings(struct kvm_cpu_context *host_ctxt) +static void handle___pkvm_host_share_hyp(struct kvm_cpu_context *host_ctxt) { - DECLARE_REG(unsigned long, start, host_ctxt, 1); - DECLARE_REG(unsigned long, size, host_ctxt, 2); - DECLARE_REG(unsigned long, phys, host_ctxt, 3); - DECLARE_REG(enum kvm_pgtable_prot, prot, host_ctxt, 4); + DECLARE_REG(u64, pfn, host_ctxt, 1); - cpu_reg(host_ctxt, 1) = __pkvm_create_mappings(start, size, phys, prot); + cpu_reg(host_ctxt, 1) = __pkvm_host_share_hyp(pfn); } static void handle___pkvm_create_private_mapping(struct kvm_cpu_context *host_ctxt) @@ -193,7 +190,7 @@ static const hcall_t host_hcall[] = { HANDLE_FUNC(__vgic_v3_restore_aprs), HANDLE_FUNC(__pkvm_init), HANDLE_FUNC(__pkvm_cpu_set_vector), - HANDLE_FUNC(__pkvm_create_mappings), + HANDLE_FUNC(__pkvm_host_share_hyp), HANDLE_FUNC(__pkvm_create_private_mapping), HANDLE_FUNC(__pkvm_prot_finalize), HANDLE_FUNC(__pkvm_mark_hyp), diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 223c541a7051..75273166d2c5 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -315,6 +315,96 @@ static int host_stage2_idmap(u64 addr) 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; + u32 level; + int ret; + + if (!range_is_memory(addr, addr + PAGE_SIZE)) + return -EINVAL; + + hyp_spin_lock(&host_kvm.lock); + hyp_spin_lock(&pkvm_pgd_lock); + + ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, &level); + 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, KVM_PGTABLE_PROT_RWX, 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, &level); + if (ret) + goto unlock; + + /* + * If the page has been shared with the hypervisor, it must be + * SHARED_BORROWED already. + */ + 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); + if (ret) + goto unlock; + + prot = pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_OWNED); + ret = host_stage2_idmap_locked(addr, addr + PAGE_SIZE, prot); + BUG_ON(ret); + +unlock: + hyp_spin_unlock(&pkvm_pgd_lock); + hyp_spin_unlock(&host_kvm.lock); + + return ret; +} + int __pkvm_mark_hyp(phys_addr_t start, phys_addr_t end) { int ret; diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 0625bf2353c2..cbab146cda6a 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -259,10 +259,8 @@ static int __create_hyp_mappings(unsigned long start, unsigned long size, { int err; - if (!kvm_host_owns_hyp_mappings()) { - return kvm_call_hyp_nvhe(__pkvm_create_mappings, - start, size, phys, prot); - } + if (WARN_ON(!kvm_host_owns_hyp_mappings())) + return -EINVAL; mutex_lock(&kvm_hyp_pgd_mutex); err = kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot); @@ -282,6 +280,21 @@ static phys_addr_t kvm_kaddr_to_phys(void *kaddr) } } +static int pkvm_share_hyp(phys_addr_t start, phys_addr_t end) +{ + phys_addr_t addr; + int ret; + + for (addr = ALIGN_DOWN(start, PAGE_SIZE); addr < end; addr += PAGE_SIZE) { + ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp, + __phys_to_pfn(addr)); + if (ret) + return ret; + } + + return 0; +} + /** * create_hyp_mappings - duplicate a kernel virtual address range in Hyp mode * @from: The virtual kernel start address of the range @@ -302,6 +315,13 @@ int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot) if (is_kernel_in_hyp_mode()) return 0; + if (!kvm_host_owns_hyp_mappings()) { + if (WARN_ON(prot != PAGE_HYP)) + return -EPERM; + return pkvm_share_hyp(kvm_kaddr_to_phys(from), + kvm_kaddr_to_phys(to)); + } + start = start & PAGE_MASK; end = PAGE_ALIGN(end); -- 2.32.0.432.gabb21c7263-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel