On 16/04/20 17:09, Marc Zyngier wrote:
> On Wed, 15 Apr 2020 18:13:56 +0200
> Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
>> On 13/04/20 14:20, Keqian Zhu wrote:
>>> There is already support of enabling dirty log graually in small chunks
>>> for x86 in commit 3c9bd4006bfc ("KVM: x86: enable dirty log gradually in
>>> small chunks"). This adds support for arm64.
>>>
>>> x86 still writes protect all huge pages when DIRTY_LOG_INITIALLY_ALL_SET
>>> is eanbled. However, for arm64, both huge pages and normal pages can be
>>> write protected gradually by userspace.
>>>
>>> Under the Huawei Kunpeng 920 2.6GHz platform, I did some tests on 128G
>>> Linux VMs with different page size. The memory pressure is 127G in each
>>> case. The time taken of memory_global_dirty_log_start in QEMU is listed
>>> below:
>>>
>>> Page Size Before After Optimization
>>> 4K 650ms 1.8ms
>>> 2M 4ms 1.8ms
>>> 1G 2ms 1.8ms
>>>
>>> Besides the time reduction, the biggest income is that we will minimize
>>> the performance side effect (because of dissloving huge pages and marking
>>> memslots dirty) on guest after enabling dirty log.
>>>
>>> Signed-off-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx>
>>> ---
>>> Documentation/virt/kvm/api.rst | 2 +-
>>> arch/arm64/include/asm/kvm_host.h | 3 +++
>>> virt/kvm/arm/mmu.c | 12 ++++++++++--
>>> 3 files changed, 14 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
>>> index efbbe570aa9b..0017f63fa44f 100644
>>> --- a/Documentation/virt/kvm/api.rst
>>> +++ b/Documentation/virt/kvm/api.rst
>>> @@ -5777,7 +5777,7 @@ will be initialized to 1 when created. This also improves performance because
>>> dirty logging can be enabled gradually in small chunks on the first call
>>> to KVM_CLEAR_DIRTY_LOG. KVM_DIRTY_LOG_INITIALLY_SET depends on
>>> KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE (it is also only available on
>>> -x86 for now).
>>> +x86 and arm64 for now).
>>>
>>> KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 was previously available under the name
>>> KVM_CAP_MANUAL_DIRTY_LOG_PROTECT, but the implementation had bugs that make
>>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>>> index 32c8a675e5a4..a723f84fab83 100644
>>> --- a/arch/arm64/include/asm/kvm_host.h
>>> +++ b/arch/arm64/include/asm/kvm_host.h
>>> @@ -46,6 +46,9 @@
>>> #define KVM_REQ_RECORD_STEAL KVM_ARCH_REQ(3)
>>> #define KVM_REQ_RELOAD_GICv4 KVM_ARCH_REQ(4)
>>>
>>> +#define KVM_DIRTY_LOG_MANUAL_CAPS (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE | \
>>> + KVM_DIRTY_LOG_INITIALLY_SET)
>>> +
>>> DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
>>>
>>> extern unsigned int kvm_sve_max_vl;
>>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
>>> index e3b9ee268823..1077f653a611 100644
>>> --- a/virt/kvm/arm/mmu.c
>>> +++ b/virt/kvm/arm/mmu.c
>>> @@ -2265,8 +2265,16 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>>> * allocated dirty_bitmap[], dirty pages will be be tracked while the
>>> * memory slot is write protected.
>>> */
>>> - if (change != KVM_MR_DELETE && mem->flags & KVM_MEM_LOG_DIRTY_PAGES)
>>> - kvm_mmu_wp_memory_region(kvm, mem->slot);
>>> + if (change != KVM_MR_DELETE && mem->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>>> + /*
>>> + * If we're with initial-all-set, we don't need to write
>>> + * protect any pages because they're all reported as dirty.
>>> + * Huge pages and normal pages will be write protect gradually.
>>> + */
>>> + if (!kvm_dirty_log_manual_protect_and_init_set(kvm)) {
>>> + kvm_mmu_wp_memory_region(kvm, mem->slot);
>>> + }
>>> + }
>>> }
>>>
>>> int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>
>>
>> Marc, what is the status of this patch?
>
> I just had a look at it. Is there any urgency for merging it?
No, I thought I was still replying to the v1.
Paolo
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