From: David Woodhouse <dwmw2@infradead.org>
To: Andy Lutomirski <luto@amacapital.net>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: KarimAllah Ahmed <karahmed@amazon.de>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Asit Mallick <asit.k.mallick@intel.com>,
Arjan Van De Ven <arjan.van.de.ven@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Andi Kleen <ak@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Dan Williams <dan.j.williams@intel.com>,
Jun Nakajima <jun.nakajima@intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Greg KH <gregkh@linuxfoundation.org>,
Andy Lutomirski <luto@kernel.org>,
Ashok Raj <ashok.raj@intel.com>,
daniel.kiper@oracle.com
Subject: Re: [PATCH] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL
Date: Sun, 28 Jan 2018 20:44:56 +0000 [thread overview]
Message-ID: <1517172296.6624.84.camel@infradead.org> (raw)
In-Reply-To: <86F5D9C0-7B11-448D-954F-D2EF6CBE80EC@amacapital.net>
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On Sun, 2018-01-28 at 12:40 -0800, Andy Lutomirski wrote:
>
> Do you mean that the host would intercept the guest WRMSR and do
> WRMSR itself? I would suggest that doing so is inconsistent with the
> docs. As specified, doing WRMSR to write 1 to IBRS does *not*
> protect the guest.
I believe it does. Guest kernel is protected from any guest userspace
predictions learned before IBRS was last set to 1 in *any* mode,
including host.
> For that matter, what are the semantics of VMRESUME doing a write to
> IBRS as part of its MSR switch? Is it treated as IBRS=1 from guest
> context?
Why does it matter? We *have* confirmed, FWIW, that VMRESUME writing 1
to IBRS as part of its MSR switch when it was already 1 is not
optimised away and *is* treated as writing IBRS=1 again.
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next prev parent reply other threads:[~2018-01-28 20:44 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-28 19:29 KarimAllah Ahmed
2018-01-28 20:21 ` Konrad Rzeszutek Wilk
2018-01-28 20:39 ` David Woodhouse
2018-01-28 20:40 ` Andy Lutomirski
2018-01-28 20:44 ` David Woodhouse [this message]
2018-01-28 20:53 ` Andy Lutomirski
2018-01-28 20:56 ` David Woodhouse
2018-01-28 21:41 ` Van De Ven, Arjan
2018-01-28 21:47 ` David Woodhouse
2018-01-29 1:06 ` KarimAllah Ahmed
2018-01-29 18:43 ` Jim Mattson
2018-01-29 19:01 ` David Woodhouse
2018-01-29 19:04 ` Jim Mattson
2018-01-29 19:10 ` KarimAllah Ahmed
2018-01-29 19:16 ` Konrad Rzeszutek Wilk
2018-01-29 19:27 ` Jim Mattson
2018-01-29 0:39 Liran Alon
2018-01-29 8:46 ` David Woodhouse
2018-01-29 9:43 ` KarimAllah Ahmed
2018-01-29 10:37 ` David Woodhouse
2018-01-29 10:55 ` Paolo Bonzini
2018-01-29 17:27 ` Konrad Rzeszutek Wilk
2018-01-29 10:47 ` Paolo Bonzini
2018-01-29 17:31 ` Konrad Rzeszutek Wilk
2018-01-29 21:49 ` Daniel Kiper
2018-01-29 23:01 ` Jim Mattson
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