Hi Quentin, On Mon, Aug 9, 2021 at 5:25 PM Quentin Perret <qperret@xxxxxxxxxx> wrote: > > Much of the stage-2 manipulation logic relies on being able to destroy > block mappings if e.g. installing a smaller mapping in the range. The > rationale for this behaviour is that stage-2 mappings can always be > re-created lazily. However, this gets more complicated when the stage-2 > page-table is used to store metadata about the underlying pages. In such > cases, destroying a block mapping may lead to losing part of the state, > and confuse the user of those metadata (such as the hypervisor in nVHE > protected mode). > > To avoid this, introduce a callback function in the pgtable struct which > is called during all map operations to determine whether the mappings > can use blocks, or should be forced to page granularity. This is used by > the hypervisor when creating the host stage-2 to force page-level > mappings when using non-default protection attributes. > > Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx> Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx> Thanks, /fuad > --- > arch/arm64/include/asm/kvm_pgtable.h | 66 +++++++++++++++++---------- > arch/arm64/kvm/hyp/nvhe/mem_protect.c | 34 ++++++++++++-- > arch/arm64/kvm/hyp/pgtable.c | 29 ++++++++++-- > 3 files changed, 94 insertions(+), 35 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > index 83c5c97d9eac..2c090b0eee77 100644 > --- a/arch/arm64/include/asm/kvm_pgtable.h > +++ b/arch/arm64/include/asm/kvm_pgtable.h > @@ -115,25 +115,6 @@ enum kvm_pgtable_stage2_flags { > KVM_PGTABLE_S2_IDMAP = BIT(1), > }; > > -/** > - * struct kvm_pgtable - KVM page-table. > - * @ia_bits: Maximum input address size, in bits. > - * @start_level: Level at which the page-table walk starts. > - * @pgd: Pointer to the first top-level entry of the page-table. > - * @mm_ops: Memory management callbacks. > - * @mmu: Stage-2 KVM MMU struct. Unused for stage-1 page-tables. > - */ > -struct kvm_pgtable { > - u32 ia_bits; > - u32 start_level; > - kvm_pte_t *pgd; > - struct kvm_pgtable_mm_ops *mm_ops; > - > - /* Stage-2 only */ > - struct kvm_s2_mmu *mmu; > - enum kvm_pgtable_stage2_flags flags; > -}; > - > /** > * enum kvm_pgtable_prot - Page-table permissions and attributes. > * @KVM_PGTABLE_PROT_X: Execute permission. > @@ -149,11 +130,43 @@ enum kvm_pgtable_prot { > KVM_PGTABLE_PROT_DEVICE = BIT(3), > }; > > -#define PAGE_HYP (KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_W) > +#define KVM_PGTABLE_PROT_RW (KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_W) > +#define KVM_PGTABLE_PROT_RWX (KVM_PGTABLE_PROT_RW | KVM_PGTABLE_PROT_X) > + > +#define PKVM_HOST_MEM_PROT KVM_PGTABLE_PROT_RWX > +#define PKVM_HOST_MMIO_PROT KVM_PGTABLE_PROT_RW > + > +#define PAGE_HYP KVM_PGTABLE_PROT_RW > #define PAGE_HYP_EXEC (KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_X) > #define PAGE_HYP_RO (KVM_PGTABLE_PROT_R) > #define PAGE_HYP_DEVICE (PAGE_HYP | KVM_PGTABLE_PROT_DEVICE) > > +typedef bool (*kvm_pgtable_force_pte_cb_t)(u64 addr, u64 end, > + enum kvm_pgtable_prot prot); > + > +/** > + * struct kvm_pgtable - KVM page-table. > + * @ia_bits: Maximum input address size, in bits. > + * @start_level: Level at which the page-table walk starts. > + * @pgd: Pointer to the first top-level entry of the page-table. > + * @mm_ops: Memory management callbacks. > + * @mmu: Stage-2 KVM MMU struct. Unused for stage-1 page-tables. > + * @flags: Stage-2 page-table flags. > + * @force_pte_cb: Function that returns true if page level mappings must > + * be used instead of block mappings. > + */ > +struct kvm_pgtable { > + u32 ia_bits; > + u32 start_level; > + kvm_pte_t *pgd; > + struct kvm_pgtable_mm_ops *mm_ops; > + > + /* Stage-2 only */ > + struct kvm_s2_mmu *mmu; > + enum kvm_pgtable_stage2_flags flags; > + kvm_pgtable_force_pte_cb_t force_pte_cb; > +}; > + > /** > * enum kvm_pgtable_walk_flags - Flags to control a depth-first page-table walk. > * @KVM_PGTABLE_WALK_LEAF: Visit leaf entries, including invalid > @@ -246,21 +259,24 @@ int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys, > u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift); > > /** > - * kvm_pgtable_stage2_init_flags() - Initialise a guest stage-2 page-table. > + * __kvm_pgtable_stage2_init() - Initialise a guest stage-2 page-table. > * @pgt: Uninitialised page-table structure to initialise. > * @arch: Arch-specific KVM structure representing the guest virtual > * machine. > * @mm_ops: Memory management callbacks. > * @flags: Stage-2 configuration flags. > + * @force_pte_cb: Function that returns true if page level mappings must > + * be used instead of block mappings. > * > * Return: 0 on success, negative error code on failure. > */ > -int kvm_pgtable_stage2_init_flags(struct kvm_pgtable *pgt, struct kvm_arch *arch, > - struct kvm_pgtable_mm_ops *mm_ops, > - enum kvm_pgtable_stage2_flags flags); > +int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_arch *arch, > + struct kvm_pgtable_mm_ops *mm_ops, > + enum kvm_pgtable_stage2_flags flags, > + kvm_pgtable_force_pte_cb_t force_pte_cb); > > #define kvm_pgtable_stage2_init(pgt, arch, mm_ops) \ > - kvm_pgtable_stage2_init_flags(pgt, arch, mm_ops, 0) > + __kvm_pgtable_stage2_init(pgt, arch, mm_ops, 0, NULL) > > /** > * kvm_pgtable_stage2_destroy() - Destroy an unused guest stage-2 page-table. > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > index 2148d3968aa5..6fed6772c673 100644 > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > @@ -89,6 +89,8 @@ static void prepare_host_vtcr(void) > id_aa64mmfr1_el1_sys_val, phys_shift); > } > > +static bool host_stage2_force_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot prot); > + > int kvm_host_prepare_stage2(void *pgt_pool_base) > { > struct kvm_s2_mmu *mmu = &host_kvm.arch.mmu; > @@ -101,8 +103,9 @@ int kvm_host_prepare_stage2(void *pgt_pool_base) > if (ret) > return ret; > > - ret = kvm_pgtable_stage2_init_flags(&host_kvm.pgt, &host_kvm.arch, > - &host_kvm.mm_ops, KVM_HOST_S2_FLAGS); > + ret = __kvm_pgtable_stage2_init(&host_kvm.pgt, &host_kvm.arch, > + &host_kvm.mm_ops, KVM_HOST_S2_FLAGS, > + host_stage2_force_pte_cb); > if (ret) > return ret; > > @@ -270,15 +273,36 @@ static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range) > return 0; > } > > +static bool host_stage2_force_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot prot) > +{ > + /* > + * Block mappings must be used with care in the host stage-2 as a > + * kvm_pgtable_stage2_map() operation targeting a page in the range of > + * an existing block will delete the block under the assumption that > + * mappings in the rest of the block range can always be rebuilt lazily. > + * That assumption is correct for the host stage-2 with RWX mappings > + * targeting memory or RW mappings targeting MMIO ranges (see > + * host_stage2_idmap() below which implements some of the host memory > + * abort logic). However, this is not safe for any other mappings where > + * the host stage-2 page-table is in fact the only place where this > + * state is stored. In all those cases, it is safer to use page-level > + * mappings, hence avoiding to lose the state because of side-effects in > + * kvm_pgtable_stage2_map(). > + */ > + if (range_is_memory(addr, end)) > + return prot != PKVM_HOST_MEM_PROT; > + else > + return prot != PKVM_HOST_MMIO_PROT; > +} > + > static int host_stage2_idmap(u64 addr) > { > - enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_W; > struct kvm_mem_range range; > bool is_memory = find_mem_range(addr, &range); > + enum kvm_pgtable_prot prot; > int ret; > > - if (is_memory) > - prot |= KVM_PGTABLE_PROT_X; > + prot = is_memory ? PKVM_HOST_MEM_PROT : PKVM_HOST_MMIO_PROT; > > hyp_spin_lock(&host_kvm.lock); > ret = host_stage2_adjust_range(addr, &range); > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 2689fcb7901d..e25d829587b9 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -452,6 +452,8 @@ int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits, > pgt->start_level = KVM_PGTABLE_MAX_LEVELS - levels; > pgt->mm_ops = mm_ops; > pgt->mmu = NULL; > + pgt->force_pte_cb = NULL; > + > return 0; > } > > @@ -489,6 +491,9 @@ struct stage2_map_data { > void *memcache; > > struct kvm_pgtable_mm_ops *mm_ops; > + > + /* Force mappings to page granularity */ > + bool force_pte; > }; > > u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift) > @@ -602,6 +607,15 @@ static bool stage2_pte_executable(kvm_pte_t pte) > return !(pte & KVM_PTE_LEAF_ATTR_HI_S2_XN); > } > > +static bool stage2_leaf_mapping_allowed(u64 addr, u64 end, u32 level, > + struct stage2_map_data *data) > +{ > + if (data->force_pte && (level < (KVM_PGTABLE_MAX_LEVELS - 1))) > + return false; > + > + return kvm_block_mapping_supported(addr, end, data->phys, level); > +} > + > static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, > kvm_pte_t *ptep, > struct stage2_map_data *data) > @@ -611,7 +625,7 @@ static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, > struct kvm_pgtable *pgt = data->mmu->pgt; > struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops; > > - if (!kvm_block_mapping_supported(addr, end, phys, level)) > + if (!stage2_leaf_mapping_allowed(addr, end, level, data)) > return -E2BIG; > > if (kvm_phys_is_valid(phys)) > @@ -655,7 +669,7 @@ static int stage2_map_walk_table_pre(u64 addr, u64 end, u32 level, > if (data->anchor) > return 0; > > - if (!kvm_block_mapping_supported(addr, end, data->phys, level)) > + if (!stage2_leaf_mapping_allowed(addr, end, level, data)) > return 0; > > data->childp = kvm_pte_follow(*ptep, data->mm_ops); > @@ -785,6 +799,7 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size, > .mmu = pgt->mmu, > .memcache = mc, > .mm_ops = pgt->mm_ops, > + .force_pte = pgt->force_pte_cb && pgt->force_pte_cb(addr, addr + size, prot), > }; > struct kvm_pgtable_walker walker = { > .cb = stage2_map_walker, > @@ -816,6 +831,7 @@ int kvm_pgtable_stage2_set_owner(struct kvm_pgtable *pgt, u64 addr, u64 size, > .memcache = mc, > .mm_ops = pgt->mm_ops, > .owner_id = owner_id, > + .force_pte = true, > }; > struct kvm_pgtable_walker walker = { > .cb = stage2_map_walker, > @@ -1057,9 +1073,11 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size) > return kvm_pgtable_walk(pgt, addr, size, &walker); > } > > -int kvm_pgtable_stage2_init_flags(struct kvm_pgtable *pgt, struct kvm_arch *arch, > - struct kvm_pgtable_mm_ops *mm_ops, > - enum kvm_pgtable_stage2_flags flags) > + > +int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_arch *arch, > + struct kvm_pgtable_mm_ops *mm_ops, > + enum kvm_pgtable_stage2_flags flags, > + kvm_pgtable_force_pte_cb_t force_pte_cb) > { > size_t pgd_sz; > u64 vtcr = arch->vtcr; > @@ -1077,6 +1095,7 @@ int kvm_pgtable_stage2_init_flags(struct kvm_pgtable *pgt, struct kvm_arch *arch > pgt->mm_ops = mm_ops; > pgt->mmu = &arch->mmu; > pgt->flags = flags; > + pgt->force_pte_cb = force_pte_cb; > > /* Ensure zeroed PGD pages are visible to the hardware walker */ > dsb(ishst); > -- > 2.32.0.605.g8dce9f2422-goog > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm