From: Borislav Petkov <bp@alien8.de>
To: Guenter Roeck <linux@roeck-us.net>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
John Stultz <john.stultz@linaro.org>,
Thomas Lendacky <Thomas.Lendacky@amd.com>
Subject: Re: [PATCH] x86/TSC: Use RDTSCP
Date: Fri, 23 Nov 2018 21:44:25 +0100 [thread overview]
Message-ID: <20181123204425.GN30697@zn.tnic> (raw)
In-Reply-To: <20181123200307.GA6223@roeck-us.net>
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 come from?
But ok, I was able to reproduce and decode myself. So if the Code:
section is correct, qemu chokes on MFENCE.
[ 0.854209] Code: 90 90 90 90 90 90 90 a1 84 37 11 cd c3 8d b4 26 00 00 00 00 8d 76 00 c3 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 90 55 89 e5 <0f> ae f0 0f 31 5d c3 8d b6 00 00 00 00 55 89 e5 57 31 ff 56 53 89
All code
========
0: 90 nop
1: 90 nop
2: 90 nop
3: 90 nop
4: 90 nop
5: 90 nop
6: 90 nop
7: a1 84 37 11 cd mov 0xcd113784,%eax
c: c3 ret
d: 8d b4 26 00 00 00 00 lea 0x0(%esi,%eiz,1),%esi
14: 8d 76 00 lea 0x0(%esi),%esi
17: c3 ret
18: 8d b4 26 00 00 00 00 lea 0x0(%esi,%eiz,1),%esi
1f: 8d b4 26 00 00 00 00 lea 0x0(%esi,%eiz,1),%esi
26: 90 nop
27: 55 push %ebp
28: 89 e5 mov %esp,%ebp
2a:* 0f ae f0 mfence <-- trapping instruction
2d: 0f 31 rdtsc
2f: 5d pop %ebp
30: c3 ret
31: 8d b6 00 00 00 00 lea 0x0(%esi),%esi
37: 55 push %ebp
38: 89 e5 mov %esp,%ebp
3a: 57 push %edi
3b: 31 ff xor %edi,%edi
3d: 56 push %esi
3e: 53 push %ebx
3f: 89 .byte 0x89
Doing this:
asm volatile(ALTERNATIVE_2("mfence", ...
fails too which confirms that P3 can't do MFENCE.
I need to think about how to handle that old cruft.
Thx for the report.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2018-11-23 20:44 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-19 18:45 [PATCH] x86/TSC: Use RDTSCP Borislav Petkov
2018-11-19 19:02 ` Lendacky, Thomas
2018-11-19 19:52 ` Andy Lutomirski
2018-11-19 20:17 ` H. Peter Anvin
2018-11-19 20:40 ` Borislav Petkov
2018-11-19 20:48 ` hpa
2018-11-20 9:11 ` [tip:x86/timers] " tip-bot for Borislav Petkov
2018-11-23 20:03 ` [PATCH] " Guenter Roeck
2018-11-23 20:22 ` hpa
2018-11-23 20:44 ` Thomas Gleixner
2018-11-23 20:44 ` Borislav Petkov [this message]
2018-11-23 21:03 ` Guenter Roeck
2018-11-23 21:07 ` Borislav Petkov
2018-12-07 18:39 ` Borislav Petkov
2019-01-16 11:59 ` [tip:x86/alternatives] " tip-bot for Borislav Petkov
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