Commits · 0day-ci/linux

When KVM runs in nVHE protected mode, use the host stage 2 to unmap the hypervisor sections by marking them as owned by the hypervisor itself. The long-term goal is to ensure the EL2 code can remain robust regardless of the host's state, so this starts by making sure the host cannot e.g. write to the .hyp sections directly. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

The host currently writes directly in EL2 per-CPU data sections from the PMU code when running in nVHE. In preparation for unmapping the EL2 sections from the host stage 2, disable PMU support in protected mode as we currently do not have a use-case for it. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

We will soon unmap the .hyp sections from the host stage 2 in Protected nVHE mode, which obviously works with at least page granularity, so make sure to align them correctly. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

When KVM runs in protected nVHE mode, make use of a stage 2 page-table to give the hypervisor some control over the host memory accesses. The host stage 2 is created lazily using large block mappings if possible, and will default to page mappings in absence of a better solution. From this point on, memory accesses from the host to protected memory regions (e.g. not 'owned' by the host) are fatal and lead to hyp_panic(). Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

We will need to read sanitized values of mmfr{0,1}_el1 at EL2 soon, so add them to the list of copied variables. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Introduce a new stage 2 configuration flag to specify that all mappings in a given page-table will be identity-mapped, as will be the case for the host. This allows to introduce sanity checks in the map path and to avoid programming errors. Suggested-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

In order to further configure stage 2 page-tables, pass flags to the init function using a new enum. The first of these flags allows to disable FWB even if the hardware supports it as we will need to do so for the host stage 2. Signed-off-by: Quentin Perret <qperret@google.com>

Since the host stage 2 will be identity mapped, and since it will own most of memory, it would preferable for performance to try and use large block mappings whenever that is possible. To ease this, introduce a new helper in the KVM page-table code which allows to search for large ranges of available IPA space. This will be used in the host memory abort path to greedily idmap large portion of the PA space. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

In order to ease their re-use in other code paths, refactor the *_map_set_prot_attr() helpers to not depend on a map_data struct. No functional change intended. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

As the host stage 2 will be identity mapped, all the .hyp memory regions and/or memory pages donated to protected guestis will have to marked invalid in the host stage 2 page-table. At the same time, the hypervisor will need a way to track the ownership of each physical page to ensure memory sharing or donation between entities (host, guests, hypervisor) is legal. In order to enable this tracking at EL2, let's use the host stage 2 page-table itself. The idea is to use the top bits of invalid mappings to store the unique identifier of the page owner. The page-table owner (the host) gets identifier 0 such that, at boot time, it owns the entire IPA space as the pgd starts zeroed. Provide kvm_pgtable_stage2_set_owner() which allows to modify the ownership of pages in the host stage 2. It re-uses most of the map() logic, but ends up creating invalid mappings instead. This impacts how we do refcount as we now need to count invalid mappings when they are used for ownership tracking. Signed-off-by: Quentin Perret <qperret@google.com>

kvm_set_invalid_pte() currently only clears bit 0 from a PTE because stage2_map_walk_table_post() needs to be able to follow the anchor. In preparation for re-using bits 63-01 from invalid PTEs, make sure to zero it entirely by ensuring to cache the anchor's child upfront. Acked-by: Will Deacon <will@kernel.org> Suggested-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

We will soon need to check if a Physical Address belongs to a memblock at EL2, so make sure to sort them so this can be done efficiently. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Extend the memory pool allocated for the hypervisor to include enough pages to map all of memory at page granularity for the host stage 2. While at it, also reserve some memory for device mappings. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

The current stage2 page-table allocator uses a memcache to get pre-allocated pages when it needs any. To allow re-using this code at EL2 which uses a concept of memory pools, make the memcache argument of kvm_pgtable_stage2_map() anonymous, and let the mm_ops zalloc_page() callbacks use it the way they need to. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Refactor __populate_fault_info() to introduce __get_fault_info() which will be used once the host is wrapped in a stage 2. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Refactor __load_guest_stage2() to introduce __load_stage2() which will be re-used when loading the host stage 2. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

In order to re-use some of the stage 2 setup code at EL2, factor parts of kvm_arm_setup_stage2() out into separate functions. No functional change intended. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Move the registers relevant to host stage 2 enablement to kvm_nvhe_init_params to prepare the ground for enabling it in later patches. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

In order to make use of the stage 2 pgtable code for the host stage 2, change kvm_s2_mmu to use a kvm_arch pointer in lieu of the kvm pointer, as the host will have the former but not the latter. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

In order to make use of the stage 2 pgtable code for the host stage 2, use struct kvm_arch in lieu of struct kvm as the host will have the former but not the latter. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Previous commits have introduced infrastructure to enable the EL2 code to manage its own stage 1 mappings. However, this was preliminary work, and none of it is currently in use. Put all of this together by elevating the mapping creation at EL2 when memory protection is enabled. In this case, the host kernel running at EL1 still creates _temporary_ EL2 mappings, only used while initializing the hypervisor, but frees them right after. As such, all calls to create_hyp_mappings() after kvm init has finished turn into hypercalls, as the host now has no 'legal' way to modify the hypevisor page tables directly. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

When memory protection is enabled, the EL2 code needs the ability to create and manage its own page-table. To do so, introduce a new set of hypercalls to bootstrap a memory management system at EL2. This leads to the following boot flow in nVHE Protected mode: 1. the host allocates memory for the hypervisor very early on, using the memblock API; 2. the host creates a set of stage 1 page-table for EL2, installs the EL2 vectors, and issues the __pkvm_init hypercall; 3. during __pkvm_init, the hypervisor re-creates its stage 1 page-table and stores it in the memory pool provided by the host; 4. the hypervisor then extends its stage 1 mappings to include a vmemmap in the EL2 VA space, hence allowing to use the buddy allocator introduced in a previous patch; 5. the hypervisor jumps back in the idmap page, switches from the host-provided page-table to the new one, and wraps up its initialization by enabling the new allocator, before returning to the host. 6. the host can free the now unused page-table created for EL2, and will now need to issue hypercalls to make changes to the EL2 stage 1 mappings instead of modifying them directly. Note that for the sake of simplifying the review, this patch focuses on the hypervisor side of things. In other words, this only implements the new hypercalls, but does not make use of them from the host yet. The host-side changes will follow in a subsequent patch. Credits to Will for __pkvm_init_switch_pgd. Acked-by: Will Deacon <will@kernel.org> Co-authored-by: Will Deacon <will@kernel.org> Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

We will soon need to turn the EL2 stage 1 MMU on and off in nVHE protected mode, so refactor the set_sctlr_el1 macro to make it usable for that purpose. Acked-by: Will Deacon <will@kernel.org> Suggested-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

In order to re-map the guest vectors at EL2 when pKVM is enabled, refactor __kvm_vector_slot2idx() and kvm_init_vector_slot() to move all the address calculation logic in a static inline function. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

We will need to do cache maintenance at EL2 soon, so compile a copy of __flush_dcache_area at EL2, and provide a copy of arm64_ftr_reg_ctrel0 as it is needed by the read_ctr macro. Signed-off-by: Quentin Perret <qperret@google.com>

Introduce the infrastructure in KVM enabling to copy CPU feature registers into EL2-owned data-structures, to allow reading sanitised values directly at EL2 in nVHE. Given that only a subset of these features are being read by the hypervisor, the ones that need to be copied are to be listed under <asm/kvm_cpufeature.h> together with the name of the nVHE variable that will hold the copy. This introduces only the infrastructure enabling this copy. The first users will follow shortly. Signed-off-by: Quentin Perret <qperret@google.com>

When memory protection is enabled, the hyp code will require a basic form of memory management in order to allocate and free memory pages at EL2. This is needed for various use-cases, including the creation of hyp mappings or the allocation of stage 2 page tables. To address these use-case, introduce a simple memory allocator in the hyp code. The allocator is designed as a conventional 'buddy allocator', working with a page granularity. It allows to allocate and free physically contiguous pages from memory 'pools', with a guaranteed order alignment in the PA space. Each page in a memory pool is associated with a struct hyp_page which holds the page's metadata, including its refcount, as well as its current order, hence mimicking the kernel's buddy system in the GFP infrastructure. The hyp_page metadata are made accessible through a hyp_vmemmap, following the concept of SPARSE_VMEMMAP in the kernel. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

In order to use the kernel list library at EL2, introduce stubs for the CONFIG_DEBUG_LIST out-of-lines calls. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

With nVHE, the host currently creates all stage 1 hypervisor mappings at EL1 during boot, installs them at EL2, and extends them as required (e.g. when creating a new VM). But in a world where the host is no longer trusted, it cannot have full control over the code mapped in the hypervisor. In preparation for enabling the hypervisor to create its own stage 1 mappings during boot, introduce an early page allocator, with minimal functionality. This allocator is designed to be used only during early bootstrap of the hyp code when memory protection is enabled, which will then switch to using a full-fledged page allocator after init. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

In order to allow the usage of code shared by the host and the hyp in static inline library functions, allow the usage of kvm_nvhe_sym() at EL2 by defaulting to the raw symbol name. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

kvm_call_hyp() has some logic to issue a function call or a hypercall depending on the EL at which the kernel is running. However, all the code compiled under __KVM_NVHE_HYPERVISOR__ is guaranteed to only run at EL2 which allows us to simplify. Add ifdefery to kvm_host.h to simplify kvm_call_hyp() in .hyp.text. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Currently, the hyp code cannot make full use of a bss, as the kernel section is mapped read-only. While this mapping could simply be changed to read-write, it would intermingle even more the hyp and kernel state than they currently are. Instead, introduce a __hyp_bss section, that uses reserved pages, and create the appropriate RW hyp mappings during KVM init. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

In preparation for enabling the creation of page-tables at EL2, factor all memory allocation out of the page-table code, hence making it re-usable with any compatible memory allocator. No functional changes intended. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Currently, the KVM page-table allocator uses a mix of put_page() and free_page() calls depending on the context even though page-allocation is always achieved using variants of __get_free_page(). Make the code consistent by using put_page() throughout, and reduce the memory management API surface used by the page-table code. This will ease factoring out page-allocation from pgtable.c, which is a pre-requisite to creating page-tables at EL2. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Move the initialization of kvm_nvhe_init_params in a dedicated function that is run early, and only once during KVM init, rather than every time the KVM vectors are set and reset. This also opens the opportunity for the hypervisor to change the init structs during boot, hence simplifying the replacement of host-provided page-table by the one the hypervisor will create for itself. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Quentin Perret <qperret@google.com>

Commits on Mar 19, 2021