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Date: Thu, 29 Sep 2022 09:52:06 -0700
From: Isaku Yamahata <isaku.yamahata@...il.com>
To: Chao Peng <chao.p.peng@...ux.intel.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
linux-api@...r.kernel.org, linux-doc@...r.kernel.org,
qemu-devel@...gnu.org, Paolo Bonzini <pbonzini@...hat.com>,
Jonathan Corbet <corbet@....net>,
Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
Hugh Dickins <hughd@...gle.com>,
Jeff Layton <jlayton@...nel.org>,
"J . Bruce Fields" <bfields@...ldses.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>,
Steven Price <steven.price@....com>,
"Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
Vlastimil Babka <vbabka@...e.cz>,
Vishal Annapurve <vannapurve@...gle.com>,
Yu Zhang <yu.c.zhang@...ux.intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
ak@...ux.intel.com, david@...hat.com, aarcange@...hat.com,
ddutile@...hat.com, dhildenb@...hat.com,
Quentin Perret <qperret@...gle.com>,
Michael Roth <michael.roth@....com>, mhocko@...e.com,
Muchun Song <songmuchun@...edance.com>, wei.w.wang@...el.com,
isaku.yamahata@...il.com
Subject: Re: [PATCH v8 6/8] KVM: Update lpage info when private/shared memory
are mixed
On Thu, Sep 15, 2022 at 10:29:11PM +0800,
Chao Peng <chao.p.peng@...ux.intel.com> wrote:
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 08abad4f3e6f..a0f198cede3d 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
...
> @@ -6894,3 +6899,115 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
> if (kvm->arch.nx_lpage_recovery_thread)
> kthread_stop(kvm->arch.nx_lpage_recovery_thread);
> }
> +
> +static bool mem_attr_is_mixed(struct kvm *kvm, unsigned int attr,
> + gfn_t start, gfn_t end)
> +{
> + XA_STATE(xas, &kvm->mem_attr_array, start);
> + gfn_t gfn = start;
> + void *entry;
> + bool shared, private;
> + bool mixed = false;
> +
> + if (attr == KVM_MEM_ATTR_SHARED) {
> + shared = true;
> + private = false;
> + } else {
> + shared = false;
> + private = true;
> + }
We don't have to care the target is shared or private. We need to check
only same or not.
> +
> + rcu_read_lock();
> + entry = xas_load(&xas);
> + while (gfn < end) {
> + if (xas_retry(&xas, entry))
> + continue;
> +
> + KVM_BUG_ON(gfn != xas.xa_index, kvm);
> +
> + if (entry)
> + private = true;
> + else
> + shared = true;
> +
> + if (private && shared) {
> + mixed = true;
> + goto out;
> + }
> +
> + entry = xas_next(&xas);
> + gfn++;
> + }
> +out:
> + rcu_read_unlock();
> + return mixed;
> +}
> +
> +static inline void update_mixed(struct kvm_lpage_info *linfo, bool mixed)
> +{
> + if (mixed)
> + linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED;
> + else
> + linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED;
> +}
> +
> +static void update_mem_lpage_info(struct kvm *kvm,
> + struct kvm_memory_slot *slot,
> + unsigned int attr,
> + gfn_t start, gfn_t end)
> +{
> + unsigned long lpage_start, lpage_end;
> + unsigned long gfn, pages, mask;
> + int level;
> +
> + for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) {
> + pages = KVM_PAGES_PER_HPAGE(level);
> + mask = ~(pages - 1);
> + lpage_start = start & mask;
> + lpage_end = (end - 1) & mask;
> +
> + /*
> + * We only need to scan the head and tail page, for middle pages
> + * we know they are not mixed.
> + */
> + update_mixed(lpage_info_slot(lpage_start, slot, level),
> + mem_attr_is_mixed(kvm, attr, lpage_start,
> + lpage_start + pages));
> +
> + if (lpage_start == lpage_end)
> + return;
> +
> + for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages)
> + update_mixed(lpage_info_slot(gfn, slot, level), false);
For >2M case, we don't have to check all entry. just check lower level case.
> +
> + update_mixed(lpage_info_slot(lpage_end, slot, level),
> + mem_attr_is_mixed(kvm, attr, lpage_end,
> + lpage_end + pages));
> + }
> +}
> +
> +void kvm_arch_update_mem_attr(struct kvm *kvm, unsigned int attr,
> + gfn_t start, gfn_t end)
> +{
> + struct kvm_memory_slot *slot;
> + struct kvm_memslots *slots;
> + struct kvm_memslot_iter iter;
> + int i;
> +
> + WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)),
> + "Unsupported mem attribute.\n");
> +
> + for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
> + slots = __kvm_memslots(kvm, i);
> +
> + kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
> + slot = iter.slot;
> + start = max(start, slot->base_gfn);
> + end = min(end, slot->base_gfn + slot->npages);
> + if (WARN_ON_ONCE(start >= end))
> + continue;
> +
> + update_mem_lpage_info(kvm, slot, attr, start, end);
> + }
> + }
> +}
Here is my updated version.
bool kvm_mem_attr_is_mixed(struct kvm_memory_slot *slot, gfn_t gfn, int level)
{
gfn_t pages = KVM_PAGES_PER_HPAGE(level);
gfn_t mask = ~(pages - 1);
struct kvm_lpage_info *linfo = lpage_info_slot(gfn & mask, slot, level);
WARN_ON_ONCE(level == PG_LEVEL_4K);
return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED;
}
#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM_ATTR
static void update_mixed(struct kvm_lpage_info *linfo, bool mixed)
{
if (mixed)
linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED;
else
linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED;
}
static bool __mem_attr_is_mixed(struct kvm *kvm, gfn_t start, gfn_t end)
{
XA_STATE(xas, &kvm->mem_attr_array, start);
bool mixed = false;
gfn_t gfn = start;
void *s_entry;
void *entry;
rcu_read_lock();
s_entry = xas_load(&xas);
entry = s_entry;
while (gfn < end) {
if (xas_retry(&xas, entry))
continue;
KVM_BUG_ON(gfn != xas.xa_index, kvm);
entry = xas_next(&xas);
if (entry != s_entry) {
mixed = true;
break;
}
gfn++;
}
rcu_read_unlock();
return mixed;
}
static bool mem_attr_is_mixed(struct kvm *kvm,
struct kvm_memory_slot *slot, int level,
gfn_t start, gfn_t end)
{
struct kvm_lpage_info *child_linfo;
unsigned long child_pages;
bool mixed = false;
unsigned long gfn;
void *entry;
if (WARN_ON_ONCE(level == PG_LEVEL_4K))
return false;
if (level == PG_LEVEL_2M)
return __mem_attr_is_mixed(kvm, start, end);
/* This assumes that level - 1 is already updated. */
rcu_read_lock();
child_pages = KVM_PAGES_PER_HPAGE(level - 1);
entry = xa_load(&kvm->mem_attr_array, start);
for (gfn = start; gfn < end; gfn += child_pages) {
child_linfo = lpage_info_slot(gfn, slot, level - 1);
if (child_linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED) {
mixed = true;
break;
}
if (xa_load(&kvm->mem_attr_array, gfn) != entry) {
mixed = true;
break;
}
}
rcu_read_unlock();
return mixed;
}
static void update_mem_lpage_info(struct kvm *kvm,
struct kvm_memory_slot *slot,
unsigned int attr,
gfn_t start, gfn_t end)
{
unsigned long lpage_start, lpage_end;
unsigned long gfn, pages, mask;
int level;
for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) {
pages = KVM_PAGES_PER_HPAGE(level);
mask = ~(pages - 1);
lpage_start = start & mask;
lpage_end = (end - 1) & mask;
/*
* We only need to scan the head and tail page, for middle pages
* we know they are not mixed.
*/
update_mixed(lpage_info_slot(lpage_start, slot, level),
mem_attr_is_mixed(kvm, slot, level,
lpage_start, lpage_start + pages));
if (lpage_start == lpage_end)
return;
for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages)
update_mixed(lpage_info_slot(gfn, slot, level), false);
update_mixed(lpage_info_slot(lpage_end, slot, level),
mem_attr_is_mixed(kvm, slot, level,
lpage_end, lpage_end + pages));
}
}
void kvm_arch_update_mem_attr(struct kvm *kvm, unsigned int attr,
gfn_t start, gfn_t end)
{
struct kvm_memory_slot *slot;
struct kvm_memslots *slots;
struct kvm_memslot_iter iter;
int idx;
int i;
WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)),
"Unsupported mem attribute.\n");
idx = srcu_read_lock(&kvm->srcu);
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
slots = __kvm_memslots(kvm, i);
kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
slot = iter.slot;
start = max(start, slot->base_gfn);
end = min(end, slot->base_gfn + slot->npages);
if (WARN_ON_ONCE(start >= end))
continue;
update_mem_lpage_info(kvm, slot, attr, start, end);
}
}
srcu_read_unlock(&kvm->srcu, idx);
}
#endif
--
Isaku Yamahata <isaku.yamahata@...il.com>
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