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Date: Sun, 27 Jan 2013 15:28:40 +0200
From: Gleb Natapov <gleb@...hat.com>
To: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@...hat.com>,
Avi Kivity <avi.kivity@...il.com>,
LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 10/12] KVM: MMU: unify the code of walking pte list
On Wed, Jan 23, 2013 at 06:09:34PM +0800, Xiao Guangrong wrote:
> Walking parent spte and walking ramp have same logic, this patch introduces
> for_each_spte_in_pte_list to integrate their code
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
> ---
> arch/x86/kvm/mmu.c | 199 ++++++++++++++++++++++------------------------
> arch/x86/kvm/mmu_audit.c | 5 +-
> 2 files changed, 97 insertions(+), 107 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 55198a1..b7da3fb 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -968,26 +968,75 @@ 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 pte_list_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 pte_list link because in such cases the
> + * information in the itererator may not be valid.
> + *
> + * Returns sptep if found, NULL otherwise.
> + */
> +static u64 *pte_list_get_first(unsigned long pte_list,
> + struct pte_list_iterator *iter)
> {
> - struct pte_list_desc *desc;
> - int i;
> + if (!pte_list)
> + return NULL;
>
> - if (!*pte_list)
> - return;
> + if (!(pte_list & 1)) {
> + iter->desc = NULL;
> + return (u64 *)pte_list;
> + }
>
> - if (!(*pte_list & 1))
> - return fn((u64 *)*pte_list);
> + iter->desc = (struct pte_list_desc *)(pte_list & ~1ul);
> + iter->pos = 0;
> + return iter->desc->sptes[iter->pos];
> +}
>
> - 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;
> +/*
> + * Must be used with a valid iterator: e.g. after pte_list_get_next().
> + *
> + * Returns sptep if found, NULL otherwise.
> + */
> +static u64 *pte_list_get_next(struct pte_list_iterator *iter)
> +{
> + if (iter->desc) {
> + if (iter->pos < PTE_LIST_EXT - 1) {
> + u64 *sptep;
> +
> + ++iter->pos;
> + sptep = iter->desc->sptes[iter->pos];
> + if (sptep)
> + return sptep;
> + }
> +
> + iter->desc = iter->desc->more;
> +
> + if (iter->desc) {
> + iter->pos = 0;
> + /* desc->sptes[0] cannot be NULL */
> + return iter->desc->sptes[iter->pos];
> + }
> }
> +
> + return NULL;
> }
>
> +#define for_each_spte_in_pte_list(pte_list, iter, spte) \
> + for (spte = pte_list_get_first(pte_list, &(iter)); \
> + spte != NULL; spte = pte_list_get_next(&(iter)))
> +
> +#define for_each_spte_in_rmap(rmap, iter, spte) \
> + for_each_spte_in_pte_list(rmap, iter, spte)
> +
> static unsigned long *__gfn_to_rmap(gfn_t gfn, int level,
> struct kvm_memory_slot *slot)
> {
> @@ -1039,67 +1088,6 @@ 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)
> -{
> - if (!rmap)
> - return NULL;
> -
> - if (!(rmap & 1)) {
> - iter->desc = NULL;
> - return (u64 *)rmap;
> - }
> -
> - iter->desc = (struct pte_list_desc *)(rmap & ~1ul);
> - iter->pos = 0;
> - return iter->desc->sptes[iter->pos];
> -}
> -
> -/*
> - * 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)
> -{
> - if (iter->desc) {
> - if (iter->pos < PTE_LIST_EXT - 1) {
> - u64 *sptep;
> -
> - ++iter->pos;
> - sptep = iter->desc->sptes[iter->pos];
> - if (sptep)
> - return sptep;
> - }
> -
> - iter->desc = iter->desc->more;
> -
> - if (iter->desc) {
> - iter->pos = 0;
> - /* desc->sptes[0] cannot be NULL */
> - return iter->desc->sptes[iter->pos];
> - }
> - }
> -
> - return NULL;
> -}
> -
> static void drop_spte(struct kvm *kvm, u64 *sptep)
> {
> if (mmu_spte_clear_track_bits(sptep))
> @@ -1160,14 +1148,13 @@ static bool __rmap_write_protect(struct kvm *kvm, unsigned long *rmapp,
> bool pt_protect)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct pte_list_iterator iter;
> bool flush = false;
>
> - for (sptep = rmap_get_first(*rmapp, &iter); sptep;) {
> + for_each_spte_in_rmap(*rmapp, iter, sptep) {
> BUG_ON(!(*sptep & PT_PRESENT_MASK));
>
> spte_write_protect(kvm, sptep, &flush, pt_protect);
> - sptep = rmap_get_next(&iter);
> }
>
> return flush;
> @@ -1221,15 +1208,14 @@ static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp,
> struct kvm_memory_slot *slot, unsigned long data)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct pte_list_iterator iter;
> int need_tlb_flush = 0;
>
> - while ((sptep = rmap_get_first(*rmapp, &iter))) {
> - BUG_ON(!(*sptep & PT_PRESENT_MASK));
> - rmap_printk("kvm_rmap_unmap_hva: spte %p %llx\n", sptep, *sptep);
> -
> +restart:
> + for_each_spte_in_rmap(*rmapp, iter, sptep) {
> drop_spte(kvm, sptep);
> need_tlb_flush = 1;
> + goto restart;
> }
>
> return need_tlb_flush;
> @@ -1239,7 +1225,7 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
> struct kvm_memory_slot *slot, unsigned long data)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct pte_list_iterator iter;
> int need_flush = 0;
> u64 new_spte;
> pte_t *ptep = (pte_t *)data;
> @@ -1248,7 +1234,8 @@ 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;) {
> +restart:
> + for_each_spte_in_rmap(*rmapp, iter, sptep) {
> BUG_ON(!is_shadow_present_pte(*sptep));
> rmap_printk("kvm_set_pte_rmapp: spte %p %llx\n", sptep, *sptep);
>
> @@ -1256,19 +1243,18 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
>
> if (pte_write(*ptep)) {
> drop_spte(kvm, sptep);
> - sptep = rmap_get_first(*rmapp, &iter);
> - } else {
> - new_spte = *sptep & ~PT64_BASE_ADDR_MASK;
> - new_spte |= (u64)new_pfn << PAGE_SHIFT;
> + goto restart;
I do not like this "goto restart" pattern throughout this patch. Follow up
patch gets rid of most of them, so they are tolerable as a temporary solution
here, but this one stays. What about moving pte_write(*ptep) outside
for_each_spte_in_rmap() loop like that:
if (pte_write(*ptep))
need_flush = kvm_unmap_rmapp();
else
for_each_spte_in_rmap() {
}
> + }
>
> - new_spte &= ~PT_WRITABLE_MASK;
> - new_spte &= ~SPTE_HOST_WRITEABLE;
> - new_spte &= ~shadow_accessed_mask;
> + new_spte = *sptep & ~PT64_BASE_ADDR_MASK;
> + new_spte |= (u64)new_pfn << PAGE_SHIFT;
>
> - mmu_spte_clear_track_bits(sptep);
> - mmu_spte_set(sptep, new_spte);
> - sptep = rmap_get_next(&iter);
> - }
> + new_spte &= ~PT_WRITABLE_MASK;
> + new_spte &= ~SPTE_HOST_WRITEABLE;
> + new_spte &= ~shadow_accessed_mask;
> +
> + mmu_spte_clear_track_bits(sptep);
> + mmu_spte_set(sptep, new_spte);
> }
>
> if (need_flush)
> @@ -1359,7 +1345,7 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
> struct kvm_memory_slot *slot, unsigned long data)
> {
> u64 *sptep;
> - struct rmap_iterator uninitialized_var(iter);
> + struct pte_list_iterator uninitialized_var(iter);
> int young = 0;
>
> /*
> @@ -1375,8 +1361,7 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
> goto out;
> }
>
> - for (sptep = rmap_get_first(*rmapp, &iter); sptep;
> - sptep = rmap_get_next(&iter)) {
> + for_each_spte_in_rmap(*rmapp, iter, sptep) {
> BUG_ON(!is_shadow_present_pte(*sptep));
>
> if (*sptep & shadow_accessed_mask) {
> @@ -1395,7 +1380,7 @@ static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
> struct kvm_memory_slot *slot, unsigned long data)
> {
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct pte_list_iterator iter;
> int young = 0;
>
> /*
> @@ -1406,8 +1391,7 @@ 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_spte_in_rmap(*rmapp, iter, sptep) {
> BUG_ON(!is_shadow_present_pte(*sptep));
>
> if (*sptep & shadow_accessed_mask) {
> @@ -1539,7 +1523,11 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
> static void mark_unsync(u64 *spte);
> static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp)
> {
> - pte_list_walk(&sp->parent_ptes, mark_unsync);
> + struct pte_list_iterator iter;
> + u64 *spte;
> +
> + for_each_spte_in_pte_list(sp->parent_ptes, iter, spte)
> + mark_unsync(spte);
> }
>
> static void mark_unsync(u64 *spte)
> @@ -2059,10 +2047,13 @@ 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 pte_list_iterator iter;
>
> - while ((sptep = rmap_get_first(sp->parent_ptes, &iter)))
> +restart:
> + for_each_spte_in_rmap(sp->parent_ptes, iter, sptep) {
> drop_parent_pte(sp, sptep);
> + goto restart;
> + }
> }
>
> static int mmu_zap_unsync_children(struct kvm *kvm,
> diff --git a/arch/x86/kvm/mmu_audit.c b/arch/x86/kvm/mmu_audit.c
> index daff69e..a08d384 100644
> --- a/arch/x86/kvm/mmu_audit.c
> +++ b/arch/x86/kvm/mmu_audit.c
> @@ -190,15 +190,14 @@ static void audit_write_protection(struct kvm *kvm, struct kvm_mmu_page *sp)
> {
> unsigned long *rmapp;
> u64 *sptep;
> - struct rmap_iterator iter;
> + struct pte_list_iterator iter;
>
> if (sp->role.direct || sp->unsync || sp->role.invalid)
> return;
>
> rmapp = gfn_to_rmap(kvm, sp->gfn, PT_PAGE_TABLE_LEVEL);
>
> - for (sptep = rmap_get_first(*rmapp, &iter); sptep;
> - sptep = rmap_get_next(&iter)) {
> + for_each_spte_in_rmap(*rmapp, iter, sptep) {
> if (is_writable_pte(*sptep))
> audit_printk(kvm, "shadow page has writable "
> "mappings: gfn %llx role %x\n",
> --
> 1.7.7.6
--
Gleb.
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