KVM ARM Archive on lore.kernel.org
 help / color / Atom feed
From: Zhenyu Ye <yezhenyu2@huawei.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: gleb@redhat.com, kvm@vger.kernel.org, "S. Tsirkin,
	Michael" <mst@redhat.com>,
	linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [Question] the check of ioeventfd collision in kvm_*assign_ioeventfd_idx
Date: Fri, 31 Jul 2020 14:39:29 +0800
Message-ID: <4aa75d90-f2d2-888c-8970-02a41f3733e4@huawei.com> (raw)
In-Reply-To: <CABgObfbFXYodCeGWSnKw0j_n2-QLxpnD_Uyc5r-_ApXv=x+qmw@mail.gmail.com>

On 2020/7/31 2:03, Paolo Bonzini wrote:
> Yes, I think it's not needed. Probably the deassign check can be turned into an assertion?
> 
> Paolo
> 

I think we can do this in the same function, and turnt he check of
p->eventfd into assertion in kvm_deassign_ioeventfd_idx(). Just like:

---8<---
static inline struct _ioeventfd *
get_ioeventfd(struct kvm *kvm, enum kvm_bus bus_idx,
              struct kvm_ioeventfd *args)
{
        static struct _ioeventfd *_p;
        bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);

        list_for_each_entry(_p, &kvm->ioeventfds, list)
                if (_p->bus_idx == bus_idx &&
                    _p->addr == args->addr &&
                    (!_p->length || !args->len ||
                     (_p->length == args->len &&
                      (_p->wildcard || wildcard ||
                       _p->datamatch == args->datamatch))))
                        return _p;

        return NULL;
}

kvm_deassign_ioeventfd_idx() {
	...
	p = get_ioeventfd(kvm, bus_idx, args);
	if (p) {
		assert(p->eventfd == eventfd);
		...
	}

---8<----

This may be easier to understand (keep the same logic in assign/deassign).

I will send a formal patch soon.

Thanks,
Zhenyu


> Il gio 30 lug 2020, 16:36 Zhenyu Ye <yezhenyu2@huawei.com <mailto:yezhenyu2@huawei.com>> ha scritto:
> 
>     Hi all,
> 
>     There are checks of ioeventfd collision in both kvm_assign_ioeventfd_idx()
>     and kvm_deassign_ioeventfd_idx(), however, with different logic.
> 
>     In kvm_assign_ioeventfd_idx(), this is done by ioeventfd_check_collision():
>     ---8<---
>             if (_p->bus_idx == p->bus_idx &&
>                 _p->addr == p->addr &&
>                 (!_p->length || !p->length ||
>                  (_p->length == p->length &&
>                   (_p->wildcard || p->wildcard ||
>                    _p->datamatch == p->datamatch))))
>                     // then we consider the two are the same
>     ---8<---
> 
>     The logic in kvm_deassign_ioeventfd_idx() is as follows:
>     ---8<---
>             if (p->bus_idx != bus_idx ||
>                 p->eventfd != eventfd  ||
>                 p->addr != args->addr  ||
>                 p->length != args->len ||
>                 p->wildcard != wildcard)
>                     continue;
> 
>             if (!p->wildcard && p->datamatch != args->datamatch)
>                     continue;
> 
>             // then we consider the two are the same
>     ---8<---
> 
>     As we can see, there is extra check of p->eventfd in
> 
>     ().  Why we don't check p->eventfd
>     in kvm_assign_ioeventfd_idx()? Or should we delete this in
>     kvm_deassign_ioeventfd_idx()?
> 
> 
>     Thanks,
>     Zhenyu
> 

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 14:19 Zhenyu Ye
2020-07-30 18:03 ` Paolo Bonzini
2020-07-31  6:39   ` Zhenyu Ye [this message]
2020-07-31  6:44     ` Paolo Bonzini
2020-07-31  8:21       ` Zhenyu Ye

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=4aa75d90-f2d2-888c-8970-02a41f3733e4@huawei.com \
    --to=yezhenyu2@huawei.com \
    --cc=gleb@redhat.com \
    --cc=kvm@vger.kernel.org \
    --cc=kvmarm@lists.cs.columbia.edu \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mst@redhat.com \
    --cc=pbonzini@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM ARM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvmarm/0 kvmarm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvmarm kvmarm/ https://lore.kernel.org/kvmarm \
		kvmarm@lists.cs.columbia.edu
	public-inbox-index kvmarm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/edu.columbia.cs.lists.kvmarm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git