From: Ben Gardon <bgardon@google.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>, Peter Xu <peterx@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Peter Shier <pshier@google.com>,
Junaid Shahid <junaids@google.com>,
Jim Mattson <jmattson@google.com>,
Yulei Zhang <yulei.kernel@gmail.com>,
Wanpeng Li <kernellwp@gmail.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
Ben Gardon <bgardon@google.com>
Subject: [PATCH v2 7/7] KVM: x86/mmu: Lazily allocate memslot rmaps
Date: Thu, 29 Apr 2021 14:18:33 -0700 [thread overview]
Message-ID: <20210429211833.3361994-8-bgardon@google.com> (raw)
In-Reply-To: <20210429211833.3361994-1-bgardon@google.com>
If the TDP MMU is in use, wait to allocate the rmaps until the shadow
MMU is actually used. (i.e. a nested VM is launched.) This saves memory
equal to 0.2% of guest memory in cases where the TDP MMU is used and
there are no nested guests involved.
Signed-off-by: Ben Gardon <bgardon@google.com>
---
arch/x86/include/asm/kvm_host.h | 11 +++++++
arch/x86/kvm/mmu/mmu.c | 21 +++++++++++--
arch/x86/kvm/mmu/mmu_internal.h | 2 +-
arch/x86/kvm/x86.c | 54 ++++++++++++++++++++++++++++++---
4 files changed, 80 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3900dcf2439e..b8633ed00a6a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1124,6 +1124,15 @@ struct kvm_arch {
#endif /* CONFIG_X86_64 */
bool shadow_mmu_active;
+
+ /*
+ * If set, the rmap should be allocated for any newly created or
+ * modified memslots. If allocating rmaps lazily, this may be set
+ * before the rmaps are allocated for existing memslots, but
+ * shadow_mmu_active will not be set until after the rmaps are fully
+ * allocated.
+ */
+ bool alloc_memslot_rmaps;
};
struct kvm_vm_stat {
@@ -1855,4 +1864,6 @@ static inline int kvm_cpu_get_apicid(int mps_cpu)
int kvm_cpu_dirty_log_size(void);
+int alloc_all_memslots_rmaps(struct kvm *kvm);
+
#endif /* _ASM_X86_KVM_HOST_H */
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index e252af46f205..b2a6585bd978 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3125,9 +3125,17 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
return ret;
}
-void activate_shadow_mmu(struct kvm *kvm)
+int activate_shadow_mmu(struct kvm *kvm)
{
+ int r;
+
+ r = alloc_all_memslots_rmaps(kvm);
+ if (r)
+ return r;
+
kvm->arch.shadow_mmu_active = true;
+
+ return 0;
}
static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa,
@@ -3300,7 +3308,9 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
}
}
- activate_shadow_mmu(vcpu->kvm);
+ r = activate_shadow_mmu(vcpu->kvm);
+ if (r)
+ return r;
write_lock(&vcpu->kvm->mmu_lock);
r = make_mmu_pages_available(vcpu);
@@ -5491,7 +5501,12 @@ void kvm_mmu_init_vm(struct kvm *kvm)
struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
if (!kvm_mmu_init_tdp_mmu(kvm))
- activate_shadow_mmu(kvm);
+ /*
+ * No memslots can have been allocated at this point.
+ * activate_shadow_mmu won't actually need to allocate
+ * rmaps, so it cannot fail.
+ */
+ WARN_ON(activate_shadow_mmu(kvm));
node->track_write = kvm_mmu_pte_write;
node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 297a911c018c..c6b21a916452 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -165,6 +165,6 @@ void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp);
void unaccount_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp);
-void activate_shadow_mmu(struct kvm *kvm);
+int activate_shadow_mmu(struct kvm *kvm);
#endif /* __KVM_X86_MMU_INTERNAL_H */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fc32a7dbe4c4..c72b35cbaef7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10842,11 +10842,24 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
kvm_page_track_free_memslot(slot);
}
-static int alloc_memslot_rmap(struct kvm_memory_slot *slot,
+static int alloc_memslot_rmap(struct kvm *kvm, struct kvm_memory_slot *slot,
unsigned long npages)
{
int i;
+ if (!kvm->arch.alloc_memslot_rmaps)
+ return 0;
+
+ /*
+ * All rmaps for a memslot should be allocated either before
+ * the memslot is installed (in which case no other threads
+ * should have a pointer to it), or under the
+ * slots_arch_lock. Avoid overwriting already allocated
+ * rmaps.
+ */
+ if (slot->arch.rmap[0])
+ return 0;
+
for (i = 0; i < KVM_NR_PAGE_SIZES; ++i) {
int lpages;
int level = i + 1;
@@ -10868,7 +10881,40 @@ static int alloc_memslot_rmap(struct kvm_memory_slot *slot,
return -ENOMEM;
}
-static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
+int alloc_memslots_rmaps(struct kvm *kvm, struct kvm_memslots *slots)
+{
+ struct kvm_memory_slot *slot;
+ int r = 0;
+
+ kvm_for_each_memslot(slot, slots) {
+ r = alloc_memslot_rmap(kvm, slot, slot->npages);
+ if (r)
+ break;
+ }
+ return r;
+}
+
+int alloc_all_memslots_rmaps(struct kvm *kvm)
+{
+ struct kvm_memslots *slots;
+ int r = 0;
+ int i;
+
+ mutex_lock(&kvm->slots_arch_lock);
+ kvm->arch.alloc_memslot_rmaps = true;
+
+ for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
+ slots = __kvm_memslots(kvm, i);
+ r = alloc_memslots_rmaps(kvm, slots);
+ if (r)
+ break;
+ }
+ mutex_unlock(&kvm->slots_arch_lock);
+ return r;
+}
+
+static int kvm_alloc_memslot_metadata(struct kvm *kvm,
+ struct kvm_memory_slot *slot,
unsigned long npages)
{
int i;
@@ -10881,7 +10927,7 @@ static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
*/
memset(&slot->arch, 0, sizeof(slot->arch));
- r = alloc_memslot_rmap(slot, npages);
+ r = alloc_memslot_rmap(kvm, slot, npages);
if (r)
return r;
@@ -10954,7 +11000,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
enum kvm_mr_change change)
{
if (change == KVM_MR_CREATE || change == KVM_MR_MOVE)
- return kvm_alloc_memslot_metadata(memslot,
+ return kvm_alloc_memslot_metadata(kvm, memslot,
mem->memory_size >> PAGE_SHIFT);
return 0;
}
--
2.31.1.527.g47e6f16901-goog
next prev parent reply other threads:[~2021-04-29 21:19 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 21:18 [PATCH v2 0/7] Lazily allocate memslot rmaps Ben Gardon
2021-04-29 21:18 ` [PATCH v2 1/7] KVM: x86/mmu: Track if shadow MMU active Ben Gardon
2021-05-03 13:42 ` Paolo Bonzini
2021-05-04 17:26 ` Ben Gardon
2021-05-04 20:18 ` Paolo Bonzini
2021-05-04 19:55 ` Sean Christopherson
2021-05-04 20:26 ` Paolo Bonzini
2021-05-04 20:36 ` Sean Christopherson
2021-04-29 21:18 ` [PATCH v2 2/7] KVM: x86/mmu: Skip rmap operations if shadow MMU inactive Ben Gardon
2021-04-29 21:18 ` [PATCH v2 3/7] KVM: x86/mmu: Deduplicate rmap freeing Ben Gardon
2021-04-29 21:18 ` [PATCH v2 4/7] KVM: x86/mmu: Factor out allocating memslot rmap Ben Gardon
2021-04-29 21:18 ` [PATCH v2 5/7] KVM: mmu: Refactor memslot copy Ben Gardon
2021-04-29 21:18 ` [PATCH v2 6/7] KVM: mmu: Add slots_arch_lock for memslot arch fields Ben Gardon
2021-05-03 13:29 ` Paolo Bonzini
2021-04-29 21:18 ` Ben Gardon [this message]
2021-05-03 13:42 ` [PATCH v2 7/7] KVM: x86/mmu: Lazily allocate memslot rmaps Paolo Bonzini
2021-05-03 17:29 ` Ben Gardon
2021-05-04 20:13 ` Sean Christopherson
2021-05-04 20:19 ` Paolo Bonzini
2021-05-04 20:34 ` Sean Christopherson
2021-05-04 20:22 ` Paolo Bonzini
2021-05-03 13:44 ` [PATCH v2 0/7] " Paolo Bonzini
2021-05-03 17:31 ` Ben Gardon
2021-05-04 7:21 ` Paolo Bonzini
2021-05-04 17:28 ` Ben Gardon
2021-05-04 18:17 ` Sean Christopherson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210429211833.3361994-8-bgardon@google.com \
--to=bgardon@google.com \
--cc=jmattson@google.com \
--cc=junaids@google.com \
--cc=kernellwp@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=peterx@redhat.com \
--cc=pshier@google.com \
--cc=seanjc@google.com \
--cc=vkuznets@redhat.com \
--cc=xiaoguangrong.eric@gmail.com \
--cc=yulei.kernel@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).