linux-kernel - Re: [PATCH v3 5/8] KVM: x86/mmu: Add a field to control memslot rmap allocation

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Date:   Fri, 7 May 2021 09:50:31 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Ben Gardon <bgardon@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        Yulei Zhang <yulei.kernel@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>,
        Kai Huang <kai.huang@...el.com>,
        Keqian Zhu <zhukeqian1@...wei.com>
Subject: Re: [PATCH v3 5/8] KVM: x86/mmu: Add a field to control memslot rmap
 allocation

On 07.05.21 01:44, Ben Gardon wrote:
> On Thu, May 6, 2021 at 11:43 AM Ben Gardon <bgardon@...gle.com> wrote:
>>
>> Add a field to control whether new memslots should have rmaps allocated
>> for them. As of this change, it's not safe to skip allocating rmaps, so
>> the field is always set to allocate rmaps. Future changes will make it
>> safe to operate without rmaps, using the TDP MMU. Then further changes
>> will allow the rmaps to be allocated lazily when needed for nested
>> oprtation.
>>
>> No functional change expected.
>>
>> Signed-off-by: Ben Gardon <bgardon@...gle.com>
>> ---
>>   arch/x86/include/asm/kvm_host.h |  8 ++++++++
>>   arch/x86/kvm/mmu/mmu.c          |  2 ++
>>   arch/x86/kvm/x86.c              | 18 +++++++++++++-----
>>   3 files changed, 23 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index ad22d4839bcc..00065f9bbc5e 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -1122,6 +1122,12 @@ struct kvm_arch {
>>           */
>>          spinlock_t tdp_mmu_pages_lock;
>>   #endif /* CONFIG_X86_64 */
>> +
>> +       /*
>> +        * If set, rmaps have been allocated for all memslots and should be
>> +        * allocated for any newly created or modified memslots.
>> +        */
>> +       bool memslots_have_rmaps;
>>   };
>>
>>   struct kvm_vm_stat {
>> @@ -1853,4 +1859,6 @@ static inline int kvm_cpu_get_apicid(int mps_cpu)
>>
>>   int kvm_cpu_dirty_log_size(void);
>>
>> +inline bool kvm_memslots_have_rmaps(struct kvm *kvm);
> 
> Woops, this shouldn't be marked inline as it creates build problems
> for the next patch with some configs.

With that fixed

Reviewed-by: David Hildenbrand <david@...hat.com>


-- 
Thanks,

David / dhildenb