From: Thomas Gleixner <tglx@linutronix.de>
To: Muhammad Usama Anjum <usama.anjum@collabora.com>,
Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>
Cc: Steven Noonan <steven@uplinklabs.net>,
usama.anjum@collabora.com, kernel@collabora.com
Subject: Re: [PATCH 1/3] x86/tsc: implement tsc=directsync for systems without IA32_TSC_ADJUST
Date: Wed, 24 Aug 2022 16:13:11 +0200 [thread overview]
Message-ID: <87v8qhybk8.ffs@tglx> (raw)
In-Reply-To: <20220808113954.345579-1-usama.anjum@collabora.com>
On Mon, Aug 08 2022 at 16:39, Muhammad Usama Anjum wrote:
> From: Steven Noonan <steven@uplinklabs.net>
>
> AMD processors don't implement any mechanism like Intel's
> IA32_TSC_ADJUST MSR to sync the TSC. Instead of just relying on the
> BIOS, TSC can be synced by calculating the difference and directly
> writing it to the TSC MSR.
Why? This has been tried before and is known to be flaky and
unrealiable.
> Add directsync flag to turn on the TSC sync when IA32_TSC_MSR isn't
> available. Attempt 1000 times or for 30 seconds before giving up.
Looping 30 seconds with interrupts disabled? Seriously?
Thanks,
tglx
next prev parent reply other threads:[~2022-08-24 14:13 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-08 11:39 [PATCH 1/3] x86/tsc: implement tsc=directsync for systems without IA32_TSC_ADJUST Muhammad Usama Anjum
2022-08-08 11:39 ` [PATCH 2/3] x86: touch clocksource watchdog after syncing TSCs Muhammad Usama Anjum
2022-08-08 11:39 ` [PATCH 3/3] x86/tsc: don't check for random warps if using direct sync Muhammad Usama Anjum
2022-08-24 14:14 ` Thomas Gleixner
2022-08-23 16:50 ` [PATCH 1/3] x86/tsc: implement tsc=directsync for systems without IA32_TSC_ADJUST Muhammad Usama Anjum
2022-08-24 14:13 ` Thomas Gleixner [this message]
2022-08-25 7:21 ` Muhammad Usama Anjum
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