[PATCH v5 02/14] KVM: arm64: Stash observed pte value in visitor context
Gavin Shan
gshan at redhat.com
Wed Nov 9 20:55:55 PST 2022
Hi Oliver,
On 11/8/22 5:56 AM, Oliver Upton wrote:
> Rather than reading the ptep all over the shop, read the ptep once from
> __kvm_pgtable_visit() and stick it in the visitor context. Reread the
> ptep after visiting a leaf in case the callback installed a new table
> underneath.
>
> No functional change intended.
>
> Signed-off-by: Oliver Upton <oliver.upton at linux.dev>
> ---
> arch/arm64/include/asm/kvm_pgtable.h | 1 +
> arch/arm64/kvm/hyp/nvhe/mem_protect.c | 5 +-
> arch/arm64/kvm/hyp/nvhe/setup.c | 7 +--
> arch/arm64/kvm/hyp/pgtable.c | 86 +++++++++++++--------------
> 4 files changed, 48 insertions(+), 51 deletions(-)
>
Reviewed-by: Gavin Shan <gshan at redhat.com>
A nit as below.
> diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
> index 607f9bb8aab4..14d4b68a1e92 100644
> --- a/arch/arm64/include/asm/kvm_pgtable.h
> +++ b/arch/arm64/include/asm/kvm_pgtable.h
> @@ -201,6 +201,7 @@ enum kvm_pgtable_walk_flags {
>
> struct kvm_pgtable_visit_ctx {
> kvm_pte_t *ptep;
> + kvm_pte_t old;
> void *arg;
> u64 addr;
> u64 end;
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index 8f5b6a36a039..d21d1b08a055 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -421,12 +421,11 @@ static int __check_page_state_visitor(const struct kvm_pgtable_visit_ctx *ctx,
> enum kvm_pgtable_walk_flags visit)
> {
> struct check_walk_data *d = ctx->arg;
> - kvm_pte_t pte = *ctx->ptep;
>
> - if (kvm_pte_valid(pte) && !addr_is_memory(kvm_pte_to_phys(pte)))
> + if (kvm_pte_valid(ctx->old) && !addr_is_memory(kvm_pte_to_phys(ctx->old)))
> return -EINVAL;
>
> - return d->get_page_state(pte) == d->desired ? 0 : -EPERM;
> + return d->get_page_state(ctx->old) == d->desired ? 0 : -EPERM;
> }
>
> static int check_page_state_range(struct kvm_pgtable *pgt, u64 addr, u64 size,
> diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
> index a293cf5eba1b..6af443c9d78e 100644
> --- a/arch/arm64/kvm/hyp/nvhe/setup.c
> +++ b/arch/arm64/kvm/hyp/nvhe/setup.c
> @@ -192,10 +192,9 @@ static int finalize_host_mappings_walker(const struct kvm_pgtable_visit_ctx *ctx
> struct kvm_pgtable_mm_ops *mm_ops = ctx->arg;
> enum kvm_pgtable_prot prot;
> enum pkvm_page_state state;
> - kvm_pte_t pte = *ctx->ptep;
> phys_addr_t phys;
>
> - if (!kvm_pte_valid(pte))
> + if (!kvm_pte_valid(ctx->old))
> return 0;
>
> /*
> @@ -210,7 +209,7 @@ static int finalize_host_mappings_walker(const struct kvm_pgtable_visit_ctx *ctx
> if (ctx->level != (KVM_PGTABLE_MAX_LEVELS - 1))
> return -EINVAL;
>
> - phys = kvm_pte_to_phys(pte);
> + phys = kvm_pte_to_phys(ctx->old);
> if (!addr_is_memory(phys))
> return -EINVAL;
>
> @@ -218,7 +217,7 @@ static int finalize_host_mappings_walker(const struct kvm_pgtable_visit_ctx *ctx
> * 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));
> + state = pkvm_getstate(kvm_pgtable_hyp_pte_prot(ctx->old));
> switch (state) {
> case PKVM_PAGE_OWNED:
> return host_stage2_set_owner_locked(phys, PAGE_SIZE, pkvm_hyp_id);
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 900c8b9c0cfc..fb3696b3a997 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -189,6 +189,7 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data,
> enum kvm_pgtable_walk_flags flags = data->walker->flags;
> struct kvm_pgtable_visit_ctx ctx = {
> .ptep = ptep,
> + .old = READ_ONCE(*ptep),
> .arg = data->walker->arg,
> .addr = data->addr,
> .end = data->end,
> @@ -196,16 +197,16 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data,
> .flags = flags,
> };
> int ret = 0;
> - kvm_pte_t *childp, pte = *ptep;
> - bool table = kvm_pte_table(pte, level);
> + kvm_pte_t *childp;
> + bool table = kvm_pte_table(ctx.old, level);
>
> if (table && (ctx.flags & KVM_PGTABLE_WALK_TABLE_PRE))
> ret = kvm_pgtable_visitor_cb(data, &ctx, KVM_PGTABLE_WALK_TABLE_PRE);
>
> if (!table && (ctx.flags & KVM_PGTABLE_WALK_LEAF)) {
> ret = kvm_pgtable_visitor_cb(data, &ctx, KVM_PGTABLE_WALK_LEAF);
> - pte = *ptep;
> - table = kvm_pte_table(pte, level);
> + ctx.old = READ_ONCE(*ptep);
> + table = kvm_pte_table(ctx.old, level);
> }
>
Since we're here, it may be worthy to have comments to explain why we need
to read the PTE again, due to page table splitting. For example, write-protection
because of dirty logging for one page, which has been mapped by a PMD entry.
> if (ret)
> @@ -217,7 +218,7 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data,
> goto out;
> }
>
> - childp = kvm_pte_follow(pte, data->pgt->mm_ops);
> + childp = kvm_pte_follow(ctx.old, data->pgt->mm_ops);
> ret = __kvm_pgtable_walk(data, childp, level + 1);
> if (ret)
> goto out;
> @@ -299,7 +300,7 @@ static int leaf_walker(const struct kvm_pgtable_visit_ctx *ctx,
> {
> struct leaf_walk_data *data = ctx->arg;
>
> - data->pte = *ctx->ptep;
> + data->pte = ctx->old;
> data->level = ctx->level;
>
> return 0;
> @@ -388,7 +389,7 @@ enum kvm_pgtable_prot kvm_pgtable_hyp_pte_prot(kvm_pte_t pte)
> static bool hyp_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
> struct hyp_map_data *data)
> {
> - kvm_pte_t new, old = *ctx->ptep;
> + kvm_pte_t new;
> u64 granule = kvm_granule_size(ctx->level), phys = data->phys;
>
> if (!kvm_block_mapping_supported(ctx, phys))
> @@ -396,11 +397,11 @@ static bool hyp_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
>
> data->phys += granule;
> new = kvm_init_valid_leaf_pte(phys, data->attr, ctx->level);
> - if (old == new)
> + if (ctx->old == new)
> return true;
> - if (!kvm_pte_valid(old))
> + if (!kvm_pte_valid(ctx->old))
> data->mm_ops->get_page(ctx->ptep);
> - else if (WARN_ON((old ^ new) & ~KVM_PTE_LEAF_ATTR_HI_SW))
> + else if (WARN_ON((ctx->old ^ new) & ~KVM_PTE_LEAF_ATTR_HI_SW))
> return false;
>
> smp_store_release(ctx->ptep, new);
> @@ -461,16 +462,16 @@ struct hyp_unmap_data {
> static int hyp_unmap_walker(const struct kvm_pgtable_visit_ctx *ctx,
> enum kvm_pgtable_walk_flags visit)
> {
> - kvm_pte_t pte = *ctx->ptep, *childp = NULL;
> + kvm_pte_t *childp = NULL;
> u64 granule = kvm_granule_size(ctx->level);
> struct hyp_unmap_data *data = ctx->arg;
> struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
>
> - if (!kvm_pte_valid(pte))
> + if (!kvm_pte_valid(ctx->old))
> return -EINVAL;
>
> - if (kvm_pte_table(pte, ctx->level)) {
> - childp = kvm_pte_follow(pte, mm_ops);
> + if (kvm_pte_table(ctx->old, ctx->level)) {
> + childp = kvm_pte_follow(ctx->old, mm_ops);
>
> if (mm_ops->page_count(childp) != 1)
> return 0;
> @@ -538,15 +539,14 @@ static int hyp_free_walker(const struct kvm_pgtable_visit_ctx *ctx,
> enum kvm_pgtable_walk_flags visit)
> {
> struct kvm_pgtable_mm_ops *mm_ops = ctx->arg;
> - kvm_pte_t pte = *ctx->ptep;
>
> - if (!kvm_pte_valid(pte))
> + if (!kvm_pte_valid(ctx->old))
> return 0;
>
> mm_ops->put_page(ctx->ptep);
>
> - if (kvm_pte_table(pte, ctx->level))
> - mm_ops->put_page(kvm_pte_follow(pte, mm_ops));
> + if (kvm_pte_table(ctx->old, ctx->level))
> + mm_ops->put_page(kvm_pte_follow(ctx->old, mm_ops));
>
> return 0;
> }
> @@ -691,7 +691,7 @@ static void stage2_put_pte(const struct kvm_pgtable_visit_ctx *ctx, struct kvm_s
> * Clear the existing PTE, and perform break-before-make with
> * TLB maintenance if it was valid.
> */
> - if (kvm_pte_valid(*ctx->ptep)) {
> + if (kvm_pte_valid(ctx->old)) {
> kvm_clear_pte(ctx->ptep);
> kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu, ctx->addr, ctx->level);
> }
> @@ -722,7 +722,7 @@ static bool stage2_leaf_mapping_allowed(const struct kvm_pgtable_visit_ctx *ctx,
> static int stage2_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
> struct stage2_map_data *data)
> {
> - kvm_pte_t new, old = *ctx->ptep;
> + kvm_pte_t new;
> u64 granule = kvm_granule_size(ctx->level), phys = data->phys;
> struct kvm_pgtable *pgt = data->mmu->pgt;
> struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
> @@ -735,14 +735,14 @@ static int stage2_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
> else
> new = kvm_init_invalid_leaf_owner(data->owner_id);
>
> - if (stage2_pte_is_counted(old)) {
> + if (stage2_pte_is_counted(ctx->old)) {
> /*
> * Skip updating the PTE if we are trying to recreate the exact
> * same mapping or only change the access permissions. Instead,
> * the vCPU will exit one more time from guest if still needed
> * and then go through the path of relaxing permissions.
> */
> - if (!stage2_pte_needs_update(old, new))
> + if (!stage2_pte_needs_update(ctx->old, new))
> return -EAGAIN;
>
> stage2_put_pte(ctx, data->mmu, mm_ops);
> @@ -773,7 +773,7 @@ static int stage2_map_walk_table_pre(const struct kvm_pgtable_visit_ctx *ctx,
> if (!stage2_leaf_mapping_allowed(ctx, data))
> return 0;
>
> - data->childp = kvm_pte_follow(*ctx->ptep, data->mm_ops);
> + data->childp = kvm_pte_follow(ctx->old, data->mm_ops);
> kvm_clear_pte(ctx->ptep);
>
> /*
> @@ -790,11 +790,11 @@ static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx,
> struct stage2_map_data *data)
> {
> struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
> - kvm_pte_t *childp, pte = *ctx->ptep;
> + kvm_pte_t *childp;
> int ret;
>
> if (data->anchor) {
> - if (stage2_pte_is_counted(pte))
> + if (stage2_pte_is_counted(ctx->old))
> mm_ops->put_page(ctx->ptep);
>
> return 0;
> @@ -819,7 +819,7 @@ static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx,
> * a table. Accesses beyond 'end' that fall within the new table
> * will be mapped lazily.
> */
> - if (stage2_pte_is_counted(pte))
> + if (stage2_pte_is_counted(ctx->old))
> stage2_put_pte(ctx, data->mmu, mm_ops);
>
> kvm_set_table_pte(ctx->ptep, childp, mm_ops);
> @@ -844,7 +844,7 @@ static int stage2_map_walk_table_post(const struct kvm_pgtable_visit_ctx *ctx,
> data->childp = NULL;
> ret = stage2_map_walk_leaf(ctx, data);
> } else {
> - childp = kvm_pte_follow(*ctx->ptep, mm_ops);
> + childp = kvm_pte_follow(ctx->old, mm_ops);
> }
>
> mm_ops->put_page(childp);
> @@ -954,23 +954,23 @@ static int stage2_unmap_walker(const struct kvm_pgtable_visit_ctx *ctx,
> struct kvm_pgtable *pgt = ctx->arg;
> struct kvm_s2_mmu *mmu = pgt->mmu;
> struct kvm_pgtable_mm_ops *mm_ops = pgt->mm_ops;
> - kvm_pte_t pte = *ctx->ptep, *childp = NULL;
> + kvm_pte_t *childp = NULL;
> bool need_flush = false;
>
> - if (!kvm_pte_valid(pte)) {
> - if (stage2_pte_is_counted(pte)) {
> + if (!kvm_pte_valid(ctx->old)) {
> + if (stage2_pte_is_counted(ctx->old)) {
> kvm_clear_pte(ctx->ptep);
> mm_ops->put_page(ctx->ptep);
> }
> return 0;
> }
>
> - if (kvm_pte_table(pte, ctx->level)) {
> - childp = kvm_pte_follow(pte, mm_ops);
> + if (kvm_pte_table(ctx->old, ctx->level)) {
> + childp = kvm_pte_follow(ctx->old, mm_ops);
>
> if (mm_ops->page_count(childp) != 1)
> return 0;
> - } else if (stage2_pte_cacheable(pgt, pte)) {
> + } else if (stage2_pte_cacheable(pgt, ctx->old)) {
> need_flush = !stage2_has_fwb(pgt);
> }
>
> @@ -982,7 +982,7 @@ static int stage2_unmap_walker(const struct kvm_pgtable_visit_ctx *ctx,
> stage2_put_pte(ctx, mmu, mm_ops);
>
> if (need_flush && mm_ops->dcache_clean_inval_poc)
> - mm_ops->dcache_clean_inval_poc(kvm_pte_follow(pte, mm_ops),
> + mm_ops->dcache_clean_inval_poc(kvm_pte_follow(ctx->old, mm_ops),
> kvm_granule_size(ctx->level));
>
> if (childp)
> @@ -1013,11 +1013,11 @@ struct stage2_attr_data {
> static int stage2_attr_walker(const struct kvm_pgtable_visit_ctx *ctx,
> enum kvm_pgtable_walk_flags visit)
> {
> - kvm_pte_t pte = *ctx->ptep;
> + kvm_pte_t pte = ctx->old;
> struct stage2_attr_data *data = ctx->arg;
> struct kvm_pgtable_mm_ops *mm_ops = data->mm_ops;
>
> - if (!kvm_pte_valid(pte))
> + if (!kvm_pte_valid(ctx->old))
> return 0;
>
> data->level = ctx->level;
> @@ -1036,7 +1036,7 @@ static int stage2_attr_walker(const struct kvm_pgtable_visit_ctx *ctx,
> * stage-2 PTE if we are going to add executable permission.
> */
> if (mm_ops->icache_inval_pou &&
> - stage2_pte_executable(pte) && !stage2_pte_executable(*ctx->ptep))
> + stage2_pte_executable(pte) && !stage2_pte_executable(ctx->old))
> mm_ops->icache_inval_pou(kvm_pte_follow(pte, mm_ops),
> kvm_granule_size(ctx->level));
> WRITE_ONCE(*ctx->ptep, pte);
> @@ -1142,13 +1142,12 @@ static int stage2_flush_walker(const struct kvm_pgtable_visit_ctx *ctx,
> {
> struct kvm_pgtable *pgt = ctx->arg;
> struct kvm_pgtable_mm_ops *mm_ops = pgt->mm_ops;
> - kvm_pte_t pte = *ctx->ptep;
>
> - if (!kvm_pte_valid(pte) || !stage2_pte_cacheable(pgt, pte))
> + if (!kvm_pte_valid(ctx->old) || !stage2_pte_cacheable(pgt, ctx->old))
> return 0;
>
> if (mm_ops->dcache_clean_inval_poc)
> - mm_ops->dcache_clean_inval_poc(kvm_pte_follow(pte, mm_ops),
> + mm_ops->dcache_clean_inval_poc(kvm_pte_follow(ctx->old, mm_ops),
> kvm_granule_size(ctx->level));
> return 0;
> }
> @@ -1200,15 +1199,14 @@ static int stage2_free_walker(const struct kvm_pgtable_visit_ctx *ctx,
> enum kvm_pgtable_walk_flags visit)
> {
> struct kvm_pgtable_mm_ops *mm_ops = ctx->arg;
> - kvm_pte_t pte = *ctx->ptep;
>
> - if (!stage2_pte_is_counted(pte))
> + if (!stage2_pte_is_counted(ctx->old))
> return 0;
>
> mm_ops->put_page(ctx->ptep);
>
> - if (kvm_pte_table(pte, ctx->level))
> - mm_ops->put_page(kvm_pte_follow(pte, mm_ops));
> + if (kvm_pte_table(ctx->old, ctx->level))
> + mm_ops->put_page(kvm_pte_follow(ctx->old, mm_ops));
>
> return 0;
> }
>
Thanks,
Gavin
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