KVM: arm64: Stash observed pte value in visitor context

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@linux.dev>
Reviewed-by: Ben Gardon <bgardon@google.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221107215644.1895162-3-oliver.upton@linux.dev

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 607f9bb..14d4b68 100644 (file)
--- 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 8f5b6a3..d21d1b0 100644 (file)
--- 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 a293cf5..6af443c 100644 (file)
--- 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 900c8b9..fb3696b 100644 (file)
--- 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);
        }
 
        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;
 }