On Mon, 19 Jul 2021 11:47:28 +0100, Quentin Perret <[email protected]> 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 > a case, 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 fix this, introduce a callback function in the pgtable struct which > is called during all map operations to determine whether the mappings > can us blocks, or should be forced to page-granularity level. This is
nit: use? > 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 <[email protected]> > --- > arch/arm64/include/asm/kvm_pgtable.h | 63 +++++++++++++++++---------- > arch/arm64/kvm/hyp/nvhe/mem_protect.c | 16 +++++-- > arch/arm64/kvm/hyp/pgtable.c | 20 +++++++-- > 3 files changed, 69 insertions(+), 30 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h > b/arch/arm64/include/asm/kvm_pgtable.h > index af62203d2f7a..dd72653314c7 100644 > --- a/arch/arm64/include/asm/kvm_pgtable.h > +++ b/arch/arm64/include/asm/kvm_pgtable.h > @@ -75,25 +75,6 @@ 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. > @@ -109,11 +90,41 @@ 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 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_want_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. > + * @want_pte_cb: Callback function used during map operations to decide > + * whether block mappings can be used to map the given IPA > + * range. > + */ > +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_want_pte_cb_t want_pte_cb; > +}; nit: does this whole definition really need to move around? > + > /** > * struct kvm_mem_range - Range of Intermediate Physical Addresses > * @start: Start of the range. > @@ -216,21 +227,25 @@ 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_full() - 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. > + * @want_pte_cb: Callback function used during map operations to decide > + * whether block mappings can be used to map the given IPA > + * range. > * > * Return: 0 on success, negative error code on failure. > */ > -int kvm_pgtable_stage2_init_flags(struct kvm_pgtable *pgt, struct kvm_arch > *arch, > +int kvm_pgtable_stage2_init_full(struct kvm_pgtable *pgt, struct kvm_arch > *arch, > struct kvm_pgtable_mm_ops *mm_ops, > - enum kvm_pgtable_stage2_flags flags); > + enum kvm_pgtable_stage2_flags flags, > + kvm_pgtable_want_pte_cb_t want_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_full(pgt, arch, mm_ops, 0, NULL) nit: in general, we use __foo() as the primitive for foo(), rather than foo_with_icing_on_top(). > > /** > * 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 58edc62be6f7..cdace80d3e28 100644 > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > @@ -89,6 +89,7 @@ static void prepare_host_vtcr(void) > id_aa64mmfr1_el1_sys_val, phys_shift); > } > > +static bool host_stage2_want_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 +102,9 @@ 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_full(&host_kvm.pgt, &host_kvm.arch, > + &host_kvm.mm_ops, KVM_HOST_S2_FLAGS, > + host_stage2_want_pte_cb); > if (ret) > return ret; > > @@ -225,9 +227,17 @@ static inline int __host_stage2_idmap(u64 start, u64 end, > __ret; \ > }) > > +static bool host_stage2_want_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot > prot) > +{ > + if (range_is_memory(addr, end)) > + return prot != KVM_PGTABLE_PROT_RWX; > + else > + return prot != KVM_PGTABLE_PROT_RW; > +} This really deserves a comment about *why* you make such decision. I also find it a bit odd that you use the permissions to decide whether to map a block or a not. It feels like the permission is more of a side effect than anything else. > + > static int host_stage2_idmap(u64 addr) > { > - enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_W; > + enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_RW; > struct kvm_mem_range range; > bool is_memory = find_mem_range(addr, &range); > int ret; > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 34cf67997a82..5bdbe7a31551 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->want_pte_cb = NULL; > + > return 0; > } > > @@ -491,6 +493,7 @@ struct stage2_map_data { > struct kvm_pgtable_mm_ops *mm_ops; > > int ret; > + bool force_pte; OK, so you have *two* mechanisms here: once to decide if a range can be mapped as a block or not, and another one to remember the result while walking the S2 PTW. This probably deserves some documentation and/or patch splitting. > }; > > u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift) > @@ -613,6 +616,9 @@ 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 (data->force_pte && (level < (KVM_PGTABLE_MAX_LEVELS - 1))) > + return -E2BIG; > + > if (!kvm_block_mapping_supported(addr, end, phys, level)) > return -E2BIG; > > @@ -660,6 +666,9 @@ static int stage2_map_walk_table_pre(u64 addr, u64 end, > u32 level, > if (data->anchor) > return 0; > > + if (data->force_pte && (level < (KVM_PGTABLE_MAX_LEVELS - 1))) > + return 0; > + > if (!kvm_block_mapping_supported(addr, end, data->phys, level)) There is something in me screaming that kvm_block_mapping_supported() should be the point where we check for these things... Or at least a helper function that takes 'data' as a parameter. > return 0; > > @@ -791,6 +800,7 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 > addr, u64 size, > .memcache = mc, > .mm_ops = pgt->mm_ops, > .ret = 0, > + .force_pte = pgt->want_pte_cb && pgt->want_pte_cb(addr, > addr + size, prot), Reading this makes me want to rename want_pte_cb() to force_pte_cb()... > }; > struct kvm_pgtable_walker walker = { > .cb = stage2_map_walker, > @@ -826,6 +836,7 @@ int kvm_pgtable_stage2_set_owner(struct kvm_pgtable *pgt, > u64 addr, u64 size, > .mm_ops = pgt->mm_ops, > .owner_id = owner_id, > .ret = 0, > + .force_pte = true, > }; > struct kvm_pgtable_walker walker = { > .cb = stage2_map_walker, > @@ -1070,9 +1081,11 @@ 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_full(struct kvm_pgtable *pgt, struct kvm_arch > *arch, > + struct kvm_pgtable_mm_ops *mm_ops, > + enum kvm_pgtable_stage2_flags flags, > + kvm_pgtable_want_pte_cb_t want_pte_cb) > { > size_t pgd_sz; > u64 vtcr = arch->vtcr; > @@ -1090,6 +1103,7 @@ 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->want_pte_cb = want_pte_cb; > > /* Ensure zeroed PGD pages are visible to the hardware walker */ > dsb(ishst); Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
