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

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Date:   Mon, 20 Jan 2020 14:45:40 +0800
From:   Peter Xu <peterx@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        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 Sun, Jan 19, 2020 at 10:01:50AM +0100, Paolo Bonzini wrote:
> 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.

Yes I think so.  I wanted to make it clear that uaddr is temporary,
however "will be invalid" could be be too strong...  Thanks,

-- 
Peter Xu