linux-kernel - Re: [PATCH v3 09/21] KVM: X86: Don't track dirty for KVM_SET_[TSS_ADDR|IDENTITY_MAP

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Message-ID: <5af8e2ff-4bde-9652-fb25-4fe1f74daae2@redhat.com>
Date:   Sun, 19 Jan 2020 10:01:50 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Peter Xu <peterx@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Christophe de Dinechin <dinechin@...hat.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Yan Zhao <yan.y.zhao@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Kevin Kevin <kevin.tian@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>
Subject: Re: [PATCH v3 09/21] KVM: X86: Don't track dirty for
 KVM_SET_[TSS_ADDR|IDENTITY_MAP_ADDR]

On 09/01/20 15:57, Peter Xu wrote:
> -int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size)
> +/*
> + * If `uaddr' is specified, `*uaddr' will be returned with the
> + * userspace address that was just allocated.  `uaddr' is only
> + * meaningful if the function returns zero, and `uaddr' will only be
> + * valid when with either the slots_lock or with the SRCU read lock
> + * held.  After we release the lock, the returned `uaddr' will be invalid.
> + */

In practice the address is still protected by the refcount, isn't it?
Only destroying the VM could invalidate it.

Paolo