From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "Hansen, Dave" <dave.hansen@intel.com>,
"bp@alien8.de" <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"x86@kernel.org" <x86@kernel.org>,
"mingo@redhat.com" <mingo@redhat.com>,
"minipli@grsecurity.net" <minipli@grsecurity.net>,
"tglx@kernel.org" <tglx@kernel.org>
Cc: "pbonzini@redhat.com" <pbonzini@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Gao, Chao" <chao.gao@intel.com>
Subject: Re: [PATCH v2] x86/shstk: Provide kernel command line knob to disable
Date: Thu, 14 May 2026 00:31:58 +0000 [thread overview]
Message-ID: <15fb40f258adfaf50bdb0e2d3ab91748559268df.camel@intel.com> (raw)
In-Reply-To: <ffd85a09-5db8-4e5c-b0c2-8bf2664464a1@grsecurity.net>
On Wed, 2026-05-13 at 22:51 +0200, Mathias Krause wrote:
> On 08.05.26 18:35, Edgecombe, Rick P wrote:
> > On Fri, 2026-05-08 at 09:23 +0200, Mathias Krause wrote:
> > > > Now that KVM uses this this feature independently of X86_FEATURE_USER_SHSTK,
> > > > it might be good to have the plain HW shstk feature exposed for just normal
> > > > runtime user use. (+Chao, for KVM CET)
> > >
> > > But that sounds more like having the need for an official chicken bit,
> > > like I was proposing, no? Using 'clearcpuid=shstk' as a workaround for
> > > whatever KVM bugs, similar in spirit to 'nousershstk', but without the
> > > kernel taint?
> >
> > For users to turn off shadow stack for guests? You can do this via the KVM API
> > in the normal way you customize guests.
>
> https://git.kernel.org/linus/2d5d3fc593c9b7e41bee86175d7b9e11f470072e
>
> Oh, well....
Heh, well, the clearcpuid would have helped debugging I guess. And that module
param turns off shadow stack for KVM, but not for userspace. So doesn't help
your CR4.CET problems I guess.
Are you planning to send another revision of the clearcpuid approach? I'm
convinced something like this is a good thing to have, so I'll probably pick it
up if you don't.
next prev parent reply other threads:[~2026-05-14 0:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-02 17:36 [PATCH v2] x86/shstk: Provide kernel command line knob to disable Mathias Krause
2026-05-04 12:09 ` Mathias Krause
2026-05-06 19:03 ` Dave Hansen
2026-05-06 22:45 ` Edgecombe, Rick P
2026-05-07 13:39 ` Mathias Krause
2026-05-07 19:53 ` Edgecombe, Rick P
2026-05-08 7:23 ` Mathias Krause
2026-05-08 16:34 ` Dave Hansen
2026-05-11 5:04 ` Mathias Krause
2026-05-08 16:35 ` Edgecombe, Rick P
2026-05-13 20:51 ` Mathias Krause
2026-05-14 0:31 ` Edgecombe, Rick P [this message]
2026-05-14 16:14 ` Mathias Krause
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