RFR: JDK-8202384: Introduce altserver jvm variant with speculative execution disabled

Erik Joelsson erik.joelsson at oracle.com
Tue Jun 5 15:47:12 UTC 2018


On 2018-06-04 23:10, David Holmes wrote:
> Sorry to be late to this party ...
> On 5/06/2018 6:10 AM, Erik Joelsson wrote:
>> New webrev: http://cr.openjdk.java.net/~erikj/8202384/webrev.02/
>> Renamed the new jvm variant to "hardened".
> As it is a hardened server build I'd prefer if that were somehow 
> reflected in the name. Though really I don't see why this should be 
> restricted this way ... to be honest I don't see hardened as a variant 
> of server vs. client vs. zero etc at all, you should be able to harden 
> any of those.
I agree, and you sort of can. By adding the jvm feature 
"no-speculative-cti" to any jvm variant, you get the flags. The name of 
the predefined variant can be discussed. I initially suggested altserver 
because I, as you, thought it should include server in the name. But 
ultimately, I don't care that much about a name. There is also little 
point in defining a whole set of predefined variants that nobody has 
requested. If we ever need more specialized variants in the same image, 
we will add them.
> So IIUC with this change we will:
> - always build JDK native code "hardened" (if toolchain supports it)
Yes, this is correct. The reason being that no significant performance 
impact was detected, so there is no cost.
> - only build hotspot "hardened" if requested; and in that case
>   - jvm.cfg will list -server and -hardened with server as default
> Is that right? I can see that we may choose to always build Oracle JDK 
> this way but it isn't clear to me that its suitable for OpenJDK. Nor 
> why hotspot is selectable but JDK is not. ??
We would prefer to always build with security features enabled, but the 
performance impact on the JVM is so high that we want to leave it to the 
user to decide, both at bulid time and at runtime. With these changes, 
Oracle will build OracleJDK, and OpenJDK, with dual JVMs by default, but 
any other person or entity just building the OpenJDK source will just 
get the server variant for now (as has been the default for a long 
time), unless they specifically ask for "hardened" or activate the new 
jvm feature (--with-jvm-feature=no-speculative-cti).

We don't see the point in giving the choice on the JDK libraries simply 
because there is no drawback to enabling the flags.

> Sorry.
> David
> -----
>> /Erik
>> On 2018-06-04 09:54, jesper.wilhelmsson at oracle.com wrote:
>>>> On 4 Jun 2018, at 17:52, Erik Joelsson <erik.joelsson at oracle.com> 
>>>> wrote:
>>>> Hello,
>>>> On 2018-06-01 14:00, Aleksey Shipilev wrote:
>>>>> On 06/01/2018 10:53 PM, Erik Joelsson wrote:
>>>>>> This patch defines flags for disabling speculative execution for 
>>>>>> GCC and Visual Studio and applies
>>>>>> them to all binaries except libjvm when available in the 
>>>>>> compiler. It defines a new jvm feature
>>>>>> no-speculative-cti, which is used to control whether to use the 
>>>>>> flags for libjvm. It also defines a
>>>>>> new jvm variant "altserver" which is the same as server, but with 
>>>>>> this new feature added.
>>>>> I think the classic name for such product configuration is 
>>>>> "hardened", no?
>>>> I don't know. I'm open to suggestions on naming.
>>> "hardened" sounds good to me.
>>> The change looks good as well.
>>> /Jesper
>>>> /Erik
>>>>> -Aleksey

More information about the hotspot-dev mailing list