Sender: Paolo Bonzini <paolo.bonzini@gmail.com>
Message-ID: <4041d98a-23df-e9ed-b245-5edd7151fec5@redhat.com>
Date:   Tue, 23 Nov 2021 09:46:34 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.2.0
Subject: Re: [RFC v2 PATCH 09/13] KVM: Introduce kvm_memfd_invalidate_range
Content-Language: en-US
To:     Chao Peng <chao.p.peng@linux.intel.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org, qemu-devel@nongnu.org
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
        Hugh Dickins <hughd@google.com>,
        Jeff Layton <jlayton@kernel.org>,
        "J . Bruce Fields" <bfields@fieldses.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Yu Zhang <yu.c.zhang@linux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        luto@kernel.org, john.ji@intel.com, susie.li@intel.com,
        jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com,
        david@redhat.com
References: <20211119134739.20218-1-chao.p.peng@linux.intel.com>
 <20211119134739.20218-10-chao.p.peng@linux.intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <20211119134739.20218-10-chao.p.peng@linux.intel.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 11/19/21 14:47, Chao Peng wrote:
> +
> +	/* Prevent memslot modification */
> +	spin_lock(&kvm->mn_invalidate_lock);
> +	kvm->mn_active_invalidate_count++;
> +	spin_unlock(&kvm->mn_invalidate_lock);
> +
> +	ret = __kvm_handle_useraddr_range(kvm, &useraddr_range);
> +
> +	spin_lock(&kvm->mn_invalidate_lock);
> +	kvm->mn_active_invalidate_count--;
> +	spin_unlock(&kvm->mn_invalidate_lock);
> +


You need to follow this with a rcuwait_wake_up as in 
kvm_mmu_notifier_invalidate_range_end.

It's probably best if you move the manipulations of 
mn_active_invalidate_count from kvm_mmu_notifier_invalidate_range_* to 
two separate functions.

Paolo