Re: [PATCH v2 07/16] KVM: MMU: introduce for_each_pte_list_spte
From: Takuya Yoshikawa
Date: Fri Apr 13 2012 - 22:44:25 EST
On Fri, 13 Apr 2012 18:12:41 +0800b
Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> wrote:
> It is used to walk all the sptes of the specified pte_list, after
> this, the code of pte_list_walk can be removed
>
> And it can restart the walking automatically if the spte is zapped
Well, I want to ask two questions:
- why do you prefer pte_list_* naming to rmap_*?
(not a big issue but just curious)
- Are you sure the whole indirection by this patch will
not introduce any regression?
(not restricted to get_dirty)
As my previous patch showed, just a slight trivial change can introduce
siginificant performance regression/improvement.
Thanks,
Takuya
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 233 +++++++++++++++++++++++-----------------------
> arch/x86/kvm/mmu_audit.c | 6 +-
> 2 files changed, 118 insertions(+), 121 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index a1c3628..4e91e94 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -900,26 +900,110 @@ static void pte_list_remove(u64 *spte, unsigned long *pte_list)
> }
> }
>
> -typedef void (*pte_list_walk_fn) (u64 *spte);
> -static void pte_list_walk(unsigned long *pte_list, pte_list_walk_fn fn)
> -{
> +/*
> + * Used by the following functions to iterate through the sptes linked by a
> + * pte_list. All fields are private and not assumed to be used outside.
> + */
> +struct spte_iterator {
> + /* private fields */
> + unsigned long *pte_list;
> + /* holds the sptep if not NULL */
> struct pte_list_desc *desc;
> - int i;
> + /* index of the sptep, -1 means the walking does not start. */
> + int pos;
> +};
>
> - if (!*pte_list)
> - return;
> +static void pte_list_walk_init(struct spte_iterator *iter,
> + unsigned long *pte_list)
> +{
> + iter->pte_list = pte_list;
> + iter->pos = -1;
> +}
> +
> +static void pte_list_walk_check_restart(struct spte_iterator *iter, u64 *spte)
> +{
> + /*
> + * If the spte is zapped, we should set 'iter->pos = -1' to restart
> + * the walk.
> + */
> + if (!is_shadow_present_pte(*spte))
> + iter->pos = -1;
> +}
> +
> +static u64 *pte_list_first(struct spte_iterator *iter)
> +{
> + unsigned long pte_list = *iter->pte_list;
> + u64 *sptep;
> +
> + if (!pte_list)
> + return NULL;
> +
> + if (!(pte_list & 1)) {
> + iter->desc = NULL;
> + iter->pos = 0;
> + sptep = (u64 *)pte_list;
> +
> + goto exit;
> + }
> +
> + iter->desc = (struct pte_list_desc *)(pte_list & ~1ul);
> + iter->pos = 0;
> + sptep = iter->desc->sptes[iter->pos];
> +
> +exit:
> + WARN_ON(sptep && !is_shadow_present_pte(*sptep));
> + return sptep;
> +}
>
> - if (!(*pte_list & 1))
> - return fn((u64 *)*pte_list);
> +static u64 *pte_list_next(struct spte_iterator *iter)
> +{
> + u64 *sptep = NULL;
>
> - desc = (struct pte_list_desc *)(*pte_list & ~1ul);
> - while (desc) {
> - for (i = 0; i < PTE_LIST_EXT && desc->sptes[i]; ++i)
> - fn(desc->sptes[i]);
> - desc = desc->more;
> + if (iter->pos < 0)
> + return pte_list_first(iter);
> +
> + if (iter->desc) {
> + if (iter->pos < PTE_LIST_EXT - 1) {
> + ++iter->pos;
> + sptep = iter->desc->sptes[iter->pos];
> + if (sptep)
> + goto exit;
> + }
> +
> + iter->desc = iter->desc->more;
> +
> + if (iter->desc) {
> + iter->pos = 0;
> + /* desc->sptes[0] cannot be NULL */
> + sptep = iter->desc->sptes[iter->pos];
> + goto exit;
> + }
> }
> +
> +exit:
> + WARN_ON(sptep && !is_shadow_present_pte(*sptep));
> + return sptep;
> }
>
> +
> +#define for_each_pte_list_spte(pte_list, iter, spte) \
> + for (pte_list_walk_init(iter, pte_list); \
> + (spte = pte_list_next(iter)) != NULL; \
> + pte_list_walk_check_restart(iter, spte))
> +
> +typedef void (*pte_list_walk_fn) (u64 *spte);
> +static void pte_list_walk(unsigned long *pte_list, pte_list_walk_fn fn)
> +{
> + struct spte_iterator iter;
> + u64 *spte;
> +
> + for_each_pte_list_spte(pte_list, &iter, spte)
> + fn(spte);
> +}
> +
> +#define for_each_rmap_spte(rmap, iter, spte) \
> + for_each_pte_list_spte(rmap, iter, spte)
> +
> static unsigned long *__gfn_to_rmap(gfn_t gfn, int level,
> struct kvm_memory_slot *slot)
> {
> @@ -974,92 +1058,19 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
> pte_list_remove(spte, rmapp);
> }
>
> -/*
> - * Used by the following functions to iterate through the sptes linked by a
> - * rmap. All fields are private and not assumed to be used outside.
> - */
> -struct rmap_iterator {
> - /* private fields */
> - struct pte_list_desc *desc; /* holds the sptep if not NULL */
> - int pos; /* index of the sptep */
> -};
> -
> -/*
> - * Iteration must be started by this function. This should also be used after
> - * removing/dropping sptes from the rmap link because in such cases the
> - * information in the itererator may not be valid.
> - *
> - * Returns sptep if found, NULL otherwise.
> - */
> -static u64 *rmap_get_first(unsigned long rmap, struct rmap_iterator *iter)
> -{
> - u64 *sptep;
> -
> - if (!rmap)
> - return NULL;
> -
> - if (!(rmap & 1)) {
> - iter->desc = NULL;
> - sptep = (u64 *)rmap;
> -
> - goto exit;
> - }
> -
> - iter->desc = (struct pte_list_desc *)(rmap & ~1ul);
> - iter->pos = 0;
> - sptep = iter->desc->sptes[iter->pos];
> -
> -exit:
> - WARN_ON(sptep && !is_shadow_present_pte(*sptep));
> - return sptep;
> -}
> -
> -/*
> - * Must be used with a valid iterator: e.g. after rmap_get_first().
> - *
> - * Returns sptep if found, NULL otherwise.
> - */
> -static u64 *rmap_get_next(struct rmap_iterator *iter)
> -{
> - u64 *sptep = NULL;
> -
> - if (iter->desc) {
> - if (iter->pos < PTE_LIST_EXT - 1) {
> - ++iter->pos;
> - sptep = iter->desc->sptes[iter->pos];
> - if (sptep)
> - goto exit;
> - }
> -
> - iter->desc = iter->desc->more;
> -
> - if (iter->desc) {
> - iter->pos = 0;
> - /* desc->sptes[0] cannot be NULL */
> - sptep = iter->desc->sptes[iter->pos];
> - goto exit;
> - }
> - }
> -
> -exit:
> - WARN_ON(sptep && !is_shadow_present_pte(*sptep));
> - return sptep;
> -}
> -
> static void drop_spte(struct kvm *kvm, u64 *sptep)
> {
> if (mmu_spte_clear_track_bits(sptep))
> rmap_remove(kvm, sptep);
> }
>
> -/* Return true if the spte is dropped. */
> -static bool spte_write_protect(struct kvm *kvm, u64 *sptep, bool large,
> +static void spte_write_protect(struct kvm *kvm, u64 *sptep, bool large,
> bool *flush)
> {
> u64 spte = *sptep;
>
> if (!is_writable_pte(spte))
> - return false;
> + return;
>
> *flush |= true;
>
> @@ -1070,32 +1081,24 @@ static bool spte_write_protect(struct kvm *kvm, u64 *sptep, bool large,
>
> drop_spte(kvm, sptep);
> --kvm->stat.lpages;
> - return true;
> + return;
> }
>
> rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
> spte = spte & ~PT_WRITABLE_MASK;
> mmu_spte_update(sptep, spte);
> -
> - return false;
> }
>
> static bool
> __rmap_write_protect(struct kvm *kvm, unsigned long *rmapp, int level)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct spte_iterator iter;
> bool write_protected = false;
>
> - for (sptep = rmap_get_first(*rmapp, &iter); sptep;) {
> - if (spte_write_protect(kvm, sptep, level > PT_PAGE_TABLE_LEVEL,
> - &write_protected)) {
> - sptep = rmap_get_first(*rmapp, &iter);
> - continue;
> - }
> -
> - sptep = rmap_get_next(&iter);
> - }
> + for_each_rmap_spte(rmapp, &iter, sptep)
> + spte_write_protect(kvm, sptep, level > PT_PAGE_TABLE_LEVEL,
> + &write_protected);
>
> return write_protected;
> }
> @@ -1147,10 +1150,10 @@ static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp,
> unsigned long data)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct spte_iterator iter;
> int need_tlb_flush = 0;
>
> - while ((sptep = rmap_get_first(*rmapp, &iter))) {
> + for_each_rmap_spte(rmapp, &iter, sptep) {
> rmap_printk("kvm_rmap_unmap_hva: spte %p %llx\n", sptep, *sptep);
>
> drop_spte(kvm, sptep);
> @@ -1164,7 +1167,7 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
> unsigned long data)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct spte_iterator iter;
> int need_flush = 0;
> u64 new_spte;
> pte_t *ptep = (pte_t *)data;
> @@ -1173,15 +1176,14 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
> WARN_ON(pte_huge(*ptep));
> new_pfn = pte_pfn(*ptep);
>
> - for (sptep = rmap_get_first(*rmapp, &iter); sptep;) {
> + for_each_rmap_spte(rmapp, &iter, sptep) {
> rmap_printk("kvm_set_pte_rmapp: spte %p %llx\n", sptep, *sptep);
>
> need_flush = 1;
>
> - if (pte_write(*ptep)) {
> + if (pte_write(*ptep))
> drop_spte(kvm, sptep);
> - sptep = rmap_get_first(*rmapp, &iter);
> - } else {
> + else {
> new_spte = *sptep & ~PT64_BASE_ADDR_MASK;
> new_spte |= (u64)new_pfn << PAGE_SHIFT;
>
> @@ -1191,7 +1193,6 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
>
> mmu_spte_clear_track_bits(sptep);
> mmu_spte_set(sptep, new_spte);
> - sptep = rmap_get_next(&iter);
> }
> }
>
> @@ -1254,7 +1255,7 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
> unsigned long data)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct spte_iterator iter;
> int young = 0;
>
> /*
> @@ -1267,8 +1268,7 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
> if (!shadow_accessed_mask)
> return kvm_unmap_rmapp(kvm, rmapp, data);
>
> - for (sptep = rmap_get_first(*rmapp, &iter); sptep;
> - sptep = rmap_get_next(&iter))
> + for_each_rmap_spte(rmapp, &iter, sptep)
> if (*sptep & PT_ACCESSED_MASK) {
> young = 1;
> clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)sptep);
> @@ -1281,7 +1281,7 @@ static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
> unsigned long data)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct spte_iterator iter;
> int young = 0;
>
> /*
> @@ -1292,8 +1292,7 @@ static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
> if (!shadow_accessed_mask)
> goto out;
>
> - for (sptep = rmap_get_first(*rmapp, &iter); sptep;
> - sptep = rmap_get_next(&iter))
> + for_each_rmap_spte(rmapp, &iter, sptep)
> if (*sptep & PT_ACCESSED_MASK) {
> young = 1;
> break;
> @@ -1955,9 +1954,9 @@ static void kvm_mmu_page_unlink_children(struct kvm *kvm,
> static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct spte_iterator iter;
>
> - while ((sptep = rmap_get_first(sp->parent_ptes, &iter)))
> + for_each_pte_list_spte(&sp->parent_ptes, &iter, sptep)
> drop_parent_pte(sp, sptep);
> }
>
> diff --git a/arch/x86/kvm/mmu_audit.c b/arch/x86/kvm/mmu_audit.c
> index 7d7d0b9..a42bd85 100644
> --- a/arch/x86/kvm/mmu_audit.c
> +++ b/arch/x86/kvm/mmu_audit.c
> @@ -193,7 +193,7 @@ static void audit_write_protection(struct kvm *kvm, struct kvm_mmu_page *sp)
> struct kvm_memory_slot *slot;
> unsigned long *rmapp;
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct spte_iterator iter;
>
> if (sp->role.direct || sp->unsync || sp->role.invalid)
> return;
> @@ -201,13 +201,11 @@ static void audit_write_protection(struct kvm *kvm, struct kvm_mmu_page *sp)
> slot = gfn_to_memslot(kvm, sp->gfn);
> rmapp = &slot->rmap[sp->gfn - slot->base_gfn];
>
> - for (sptep = rmap_get_first(*rmapp, &iter); sptep;
> - sptep = rmap_get_next(&iter)) {
> + for_each_rmap_spte(rmapp, &iter, sptep)
> if (is_writable_pte(*sptep))
> audit_printk(kvm, "shadow page has writable "
> "mappings: gfn %llx role %x\n",
> sp->gfn, sp->role.word);
> - }
> }
>
> static void audit_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
> --
> 1.7.7.6
>
> --
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--
Takuya Yoshikawa <takuya.yoshikawa@xxxxxxxxx>
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