From: Thomas Gleixner <tglx@linutronix.de>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Dave Hansen <dave.hansen@intel.com>
Cc: Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Jun Nakajima <jun.nakajima@intel.com>,
x86@kernel.org, linux-coco@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/tdx: Mark TSC reliable
Date: Thu, 24 Aug 2023 17:49:05 +0200 [thread overview]
Message-ID: <87bkewcufi.ffs@tglx> (raw)
In-Reply-To: <20230808200111.nz74tmschph435ri@box>
On Tue, Aug 08 2023 at 23:01, Kirill A. Shutemov wrote:
> On Tue, Aug 08, 2023 at 10:13:05AM -0700, Dave Hansen wrote:
>> I take it this is carved in stone in the TDX specs somewhere. A
>> reference would be nice.
>
> TDX Module 1.0 spec:
>
> 5.3.5. Time Stamp Counter (TSC)
>
> TDX provides a trusted virtual TSC to the guest TDs. TSC value is
> monotonously incrementing, starting from 0 on TD initialization by the
> host VMM. The deviation between virtual TSC values read by each VCPU is
> small.
Nice weasel wording. What's the definition of "small"?
Any OS needs a guarantee that vCPUs cannot observe time going backwards,
which is obviously possible when the deviation is not small enough.
> Wording in the spec looks okay to me. We can only hope that implementation
> going to be sane.
Hope dies last :)
next prev parent reply other threads:[~2023-08-24 15:49 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-08 16:23 [PATCH] x86/tdx: Mark TSC reliable Kirill A. Shutemov
2023-08-08 17:13 ` Dave Hansen
2023-08-08 20:01 ` Kirill A. Shutemov
2023-08-09 5:44 ` Reshetova, Elena
2023-08-09 6:13 ` Kirill A. Shutemov
2023-08-22 23:39 ` Erdem Aktas
2023-08-24 15:49 ` Thomas Gleixner [this message]
2023-08-25 13:52 ` Kirill A. Shutemov
2023-08-25 17:09 ` Thomas Gleixner
2023-08-29 16:01 ` Nakajima, Jun
2023-08-30 7:33 ` Thomas Gleixner
2023-08-31 15:16 ` Nakajima, Jun
2023-08-24 19:31 ` Thomas Gleixner
2023-08-25 13:47 ` Kirill A. Shutemov
2023-08-25 15:16 ` Sean Christopherson
2023-09-07 17:25 ` Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87bkewcufi.ffs@tglx \
--to=tglx@linutronix.de \
--cc=bp@alien8.de \
--cc=dave.hansen@intel.com \
--cc=elena.reshetova@intel.com \
--cc=jun.nakajima@intel.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-coco@lists.linux.dev \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=sathyanarayanan.kuppuswamy@linux.intel.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox