linux-kernel - Re: [PATCH 1/2] KVM: fix cache stale memslot info with correct mmio generation number

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALzav=eXu8VmPpqSYikY5y5QqivJ_FD0N2bGTUPnAesJ2PvW1w@mail.gmail.com>
Date:	Mon, 18 Aug 2014 22:00:33 -0700
From:	David Matlack <dmatlack@...gle.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	Gleb Natapov <gleb@...nel.org>,
	Avi Kivity <avi.kivity@...il.com>, mtosatti@...hat.com,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: fix cache stale memslot info with correct mmio
 generation number

On Mon, Aug 18, 2014 at 9:41 PM, Xiao Guangrong
<xiaoguangrong@...ux.vnet.ibm.com> wrote:
> On 08/19/2014 12:31 PM, David Matlack wrote:
>> But it looks like you basically said the same thing earlier, so I think
>> we're on the same page.
>>
>
> Yes, that is what i try to explain in previous mails. :(

I'm glad we understand each other now! Sorry again for my confusion.

>> The single line patch I suggested was only intended to fix the "forever
>> incorrectly exit mmio".
>
> My patch also fixes this case and that does not doubly increase the
> number. I think this is the better one.

I prefer doubly increasing the generation for this reason: the updated boolean
requires extra code on the "client-side" to check if there's an update in
progress. And that makes it easy to get wrong. In fact, your patch
forgot to check the updated bit in mark_mmio_spte(). Doubly increasing the
generation requires no "client-side" code to work.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/