linux-kernel - Re: [Xen-devel] [RFC 2/2] x86, vdso, pvclock: Simplify and speed up the vdso pvclock reader

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: <5499897D.3000904@oracle.com>
Date:	Tue, 23 Dec 2014 10:25:49 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Paolo Bonzini <pbonzini@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Gleb Natapov <gleb@...nel.org>,
	"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm list <kvm@...r.kernel.org>
Subject: Re: [Xen-devel] [RFC 2/2] x86, vdso, pvclock: Simplify and speed
 up the vdso pvclock reader

On 12/23/2014 10:14 AM, Paolo Bonzini wrote:
>
> On 23/12/2014 16:14, Boris Ostrovsky wrote:
>>> +    do {
>>> +        version = pvti->version;
>>> +
>>> +        /* This is also a read barrier, so we'll read version first. */
>>> +        rdtsc_barrier();
>>> +        tsc = __native_read_tsc();
>>
>> This will cause VMEXIT on Xen with TSC_MODE_ALWAYS_EMULATE which is
>> used, for example, after guest migrated (unless HW is capable of scaling
>> TSC rate).
> So does the __pvclock_read_cycles this is replacing (via
> pvclock_get_nsec_offset).

Right, I didn't notice that.

-boris
--
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/