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From: Borislav Petkov <bp@alien8.de>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Wanpeng Li" <kernellwp@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
	"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH] KVM: X86: Allow userspace to define the microcode version
Date: Mon, 26 Feb 2018 13:15:09 +0100	[thread overview]
Message-ID: <20180226121509.GE4377@pd.tnic> (raw)
In-Reply-To: <46cecef2-b0fb-b0c2-bbf3-983328d52763@redhat.com>

On Mon, Feb 26, 2018 at 12:54:52PM +0100, Paolo Bonzini wrote:
> I don't understand how one thing follows from the other.  How are writes
> to 0x8B related to having a virtualized microcode loaded (which is a
> concept that actually makes no sense at all)?

I'm questioning the whole idea. 0x8b is the MSR which gives you the
microcode revision. Most CPUs don't even allow writing to it, AFAICT.
(SDM says "may prevent writing" on VM transitions.)

So how is that host-initiated write to 0x8b is even going to work, in
reality? kvm module writes the microcode version in there? How does the
admin work around that?

> It has already been fixed for a few months, and fixing it is indeed the
> right thing to do independent of this patch.

Yap.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

  reply	other threads:[~2018-02-26 12:15 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-26  7:23 [PATCH] KVM: X86: Allow userspace to define the microcode version Wanpeng Li
2018-02-26  9:41 ` Borislav Petkov
2018-02-26 10:06   ` Wanpeng Li
2018-02-26 10:49     ` Borislav Petkov
2018-02-26 11:02       ` Wanpeng Li
2018-02-26 11:16         ` Borislav Petkov
2018-02-26 11:25           ` Wanpeng Li
2018-02-26 11:30             ` Borislav Petkov
2018-02-26 11:37               ` Wanpeng Li
2018-02-26 11:44                 ` Borislav Petkov
2018-02-26 11:52                   ` Wanpeng Li
2018-02-26 11:54                   ` Paolo Bonzini
2018-02-26 12:15                     ` Borislav Petkov [this message]
2018-02-26 12:16                       ` Paolo Bonzini
2018-02-26 12:18                         ` Paolo Bonzini
2018-02-26 12:22                           ` Borislav Petkov
2018-02-26 12:41                             ` Paolo Bonzini
2018-02-26 13:05                               ` Borislav Petkov
2018-02-26 14:39                               ` Konrad Rzeszutek Wilk
2018-02-26 14:46                                 ` Paolo Bonzini
2018-02-26 19:37                                 ` Borislav Petkov
2018-02-26 20:51                                   ` Konrad Rzeszutek Wilk
2018-02-26 21:30                                     ` Konrad Rzeszutek Wilk
2018-02-27  8:33                                       ` Paolo Bonzini
2018-03-08  9:24                                       ` [tip:x86/pti] x86/spectre_v2: Don't check microcode versions when running under hypervisors tip-bot for Konrad Rzeszutek Wilk
2018-04-17 10:40                               ` [PATCH] KVM: X86: Allow userspace to define the microcode version Wanpeng Li
2018-04-17 20:24                                 ` Eduardo Habkost
2018-04-18  3:24                                   ` Wanpeng Li
2018-04-18  9:03                                     ` Eduardo Habkost
2018-04-18 10:36                                       ` Paolo Bonzini
2018-04-23 12:58                                         ` Borislav Petkov
2018-04-23 13:08                                           ` Eduardo Habkost
2018-04-23 13:23                                             ` Borislav Petkov
2018-04-23 16:03                                           ` Paolo Bonzini
2018-04-24  2:59                                         ` Wanpeng Li
2018-04-24  3:14                                           ` Konrad Rzeszutek Wilk
2018-04-24  5:09                                             ` Paolo Bonzini
2018-04-24 13:44                                               ` Konrad Rzeszutek Wilk
2018-04-24  2:56                               ` Wanpeng Li
2018-02-26 11:47       ` Paolo Bonzini
2018-02-26 12:20         ` Borislav Petkov
2018-02-26  9:26 Liran Alon
2018-02-26 10:08 ` Wanpeng Li

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