From: Fuad Tabba <tabba@google.com>
To: Quentin Perret <qperret@google.com>
Cc: maz@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com,
suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
ardb@kernel.org, qwandor@google.com, dbrazdil@google.com,
kernel-team@android.com
Subject: Re: [PATCH v4 17/21] KVM: arm64: Mark host bss and rodata section as shared
Date: Tue, 10 Aug 2021 06:40:55 +0200 [thread overview]
Message-ID: <CA+EHjTxM1QA30k4ZzajmQftZWtSR7QPVaSfVOMgpJH7GPHT+Fw@mail.gmail.com> (raw)
In-Reply-To: <20210809152448.1810400-18-qperret@google.com>
Hi Quentin,
On Mon, Aug 9, 2021 at 5:25 PM Quentin Perret <qperret@google.com> 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 <qperret@google.com>
> ---
Reviewed-by: Fuad Tabba <tabba@google.com>
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
>
next prev parent reply other threads:[~2021-08-10 4:41 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-09 15:24 [PATCH v4 00/21] Track shared pages at EL2 in protected mode Quentin Perret
2021-08-09 15:24 ` [PATCH v4 01/21] KVM: arm64: Add hyp_spin_is_locked() for basic locking assertions at EL2 Quentin Perret
2021-08-09 15:24 ` [PATCH v4 02/21] KVM: arm64: Introduce hyp_assert_lock_held() Quentin Perret
2021-08-09 15:24 ` [PATCH v4 03/21] KVM: arm64: Provide the host_stage2_try() helper macro Quentin Perret
2021-08-09 15:24 ` [PATCH v4 04/21] KVM: arm64: Introduce helper to retrieve a PTE and its level Quentin Perret
2021-08-17 13:53 ` Andrew Walbran
2021-08-09 15:24 ` [PATCH v4 05/21] KVM: arm64: Expose page-table helpers Quentin Perret
2021-08-10 4:56 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 06/21] KVM: arm64: Optimize host memory aborts Quentin Perret
2021-08-09 15:24 ` [PATCH v4 07/21] KVM: arm64: Rename KVM_PTE_LEAF_ATTR_S2_IGNORED Quentin Perret
2021-08-09 15:24 ` [PATCH v4 08/21] KVM: arm64: Don't overwrite software bits with owner id Quentin Perret
2021-08-09 15:24 ` [PATCH v4 09/21] KVM: arm64: Tolerate re-creating hyp mappings to set software bits Quentin Perret
2021-08-09 15:24 ` [PATCH v4 10/21] KVM: arm64: Enable forcing page-level stage-2 mappings Quentin Perret
2021-08-10 4:33 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 11/21] KVM: arm64: Allow populating software bits Quentin Perret
2021-08-10 4:56 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 12/21] KVM: arm64: Add helpers to tag shared pages in SW bits Quentin Perret
2021-08-09 15:24 ` [PATCH v4 13/21] KVM: arm64: Expose host stage-2 manipulation helpers Quentin Perret
2021-08-10 4:36 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 14/21] KVM: arm64: Expose pkvm_hyp_id Quentin Perret
2021-08-10 4:57 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 15/21] KVM: arm64: Introduce addr_is_memory() Quentin Perret
2021-08-10 4:37 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 16/21] KVM: arm64: Enable retrieving protections attributes of PTEs Quentin Perret
2021-08-10 4:38 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 17/21] KVM: arm64: Mark host bss and rodata section as shared Quentin Perret
2021-08-10 4:40 ` Fuad Tabba [this message]
2021-08-09 15:24 ` [PATCH v4 18/21] KVM: arm64: Remove __pkvm_mark_hyp Quentin Perret
2021-08-10 4:55 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 19/21] KVM: arm64: Refactor protected nVHE stage-1 locking Quentin Perret
2021-08-10 4:41 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 20/21] KVM: arm64: Restrict EL2 stage-1 changes in protected mode Quentin Perret
2021-08-10 4:43 ` Fuad Tabba
2021-08-09 15:24 ` [PATCH v4 21/21] KVM: arm64: Make __pkvm_create_mappings static Quentin Perret
2021-08-10 4:55 ` Fuad Tabba
2021-08-11 11:25 ` [PATCH v4 00/21] Track shared pages at EL2 in protected mode Marc Zyngier
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