[PATCH v3 02/15] KVM: arm64: Stash observed pte value in visitor context

Oliver Upton
2022-10-27T22:18:30Z

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>
---
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(-)

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);
}

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;
}
--
2.38.1.273.g43a17bfeac-goog