Ok,
I have something which looks like it works here, even with the pentium3
qemu CPU. I'll be hammering on it in the coming days but if you wanna
give it a try, here's a conglomerate patch:
---
>From 0c6adce02d2e7f3b5bbdc4cbe3eb3dae99448def Mon Sep 17 00:00:00 2001
From: Borislav Petkov
Date: Fr
On Fri, Nov 23, 2018 at 01:03:25PM -0800, Guenter Roeck wrote:
> It is a cut off screen log. x86 boots change xterm configuration from
> wrap to non-wrap, and I did a cut-and-paste instead of copying the log
> to a file. Sorry for that.
No worries.
It was a head-scratcher though because look what
On 11/23/18 12:44 PM, Borislav Petkov wrote:
On Fri, Nov 23, 2018 at 12:03:07PM -0800, Guenter Roeck wrote:
[0.762832] EIP: read_tsc+0x4/0x10
[0.762832] Code: 00 01 00 eb 89 90 55 89 e5 5d c3 90 90 90 90 90 90 90 90 90 90
90 55 a1 44 5a 8b c5 89 e5 5d c3 8d b6 00 00 00 00 55 89 e5 57 <0
On Fri, Nov 23, 2018 at 12:03:07PM -0800, Guenter Roeck wrote:
> [0.762832] EIP: read_tsc+0x4/0x10
> [0.762832] Code: 00 01 00 eb 89 90 55 89 e5 5d c3 90 90 90 90 90 90 90 90
> 90 90 90 55 a1 44 5a 8b c5 89 e5 5d c3 8d b6 00 00 00 00 55 89 e5 57 <0f> ae
> f0b
Where does that 'b' in f0b c
On Fri, 23 Nov 2018, h...@zytor.com wrote:
> On November 23, 2018 12:03:07 PM PST, Guenter Roeck
> wrote:
> ># first bad commit: [2e94061096c5c3aa6c3fe3ec2bec176c1f9c1b07] x86/TSC:
> >Use RDTSCP
>
> Right, because that cpu predates RDTSCP, so it needs to use a fallback.
Well, that's not the pro
On November 23, 2018 12:03:07 PM PST, Guenter Roeck wrote:
>Hi,
>
>On Mon, Nov 19, 2018 at 07:45:56PM +0100, Borislav Petkov wrote:
>> From: Borislav Petkov
>>
>> Currently, the kernel uses
>>
>> [LM]FENCE; RDTSC
>>
>> in the timekeeping code, to guarantee monotonicity of time where the
>> *
Hi,
On Mon, Nov 19, 2018 at 07:45:56PM +0100, Borislav Petkov wrote:
> From: Borislav Petkov
>
> Currently, the kernel uses
>
> [LM]FENCE; RDTSC
>
> in the timekeeping code, to guarantee monotonicity of time where the
> *FENCE is selected based on vendor.
>
> Replace that sequence with RDTS
On November 19, 2018 12:40:25 PM PST, Borislav Petkov wrote:
>On Mon, Nov 19, 2018 at 12:17:35PM -0800, H. Peter Anvin wrote:
>> On 11/19/18 11:52 AM, Andy Lutomirski wrote:
>> >
>> > I thought I benchmarked this on Intel at some point and found the
>> > LFENCE;RDTSC variant to be slightly faster
On Mon, Nov 19, 2018 at 12:17:35PM -0800, H. Peter Anvin wrote:
> On 11/19/18 11:52 AM, Andy Lutomirski wrote:
> >
> > I thought I benchmarked this on Intel at some point and found the
> > LFENCE;RDTSC variant to be slightly faster. But I believe you, so:
> >
> > Acked-by: Andy Lutomirski
> >
On 11/19/18 11:52 AM, Andy Lutomirski wrote:
>
> I thought I benchmarked this on Intel at some point and found the
> LFENCE;RDTSC variant to be slightly faster. But I believe you, so:
>
> Acked-by: Andy Lutomirski
>
As long as the difference isn't significant, the simplicity would seem to be
On Mon, Nov 19, 2018 at 10:46 AM Borislav Petkov wrote:
>
> From: Borislav Petkov
>
> Currently, the kernel uses
>
> [LM]FENCE; RDTSC
>
> in the timekeeping code, to guarantee monotonicity of time where the
> *FENCE is selected based on vendor.
>
> Replace that sequence with RDTSCP which is fas
On 11/19/2018 12:45 PM, Borislav Petkov wrote:
> From: Borislav Petkov
>
> Currently, the kernel uses
>
> [LM]FENCE; RDTSC
>
> in the timekeeping code, to guarantee monotonicity of time where the
> *FENCE is selected based on vendor.
>
> Replace that sequence with RDTSCP which is faster or o
From: Borislav Petkov
Currently, the kernel uses
[LM]FENCE; RDTSC
in the timekeeping code, to guarantee monotonicity of time where the
*FENCE is selected based on vendor.
Replace that sequence with RDTSCP which is faster or on-par and gives
the same guarantees.
A microbenchmark on Intel sho
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