All of lore.kernel.org
 help / color / mirror / Atom feed
From: Paolo Bonzini <pbonzini@redhat.com>
To: Borislav Petkov <bp@alien8.de>
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 13:18:07 +0100	[thread overview]
Message-ID: <3866d359-0ef8-6a99-6254-84890be62b93@redhat.com> (raw)
In-Reply-To: <24cd527d-5287-f0be-ffe8-eab341bf1d94@redhat.com>

On 26/02/2018 13:16, Paolo Bonzini wrote:
> On 26/02/2018 13:15, Borislav Petkov wrote:
>> 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?
> 
> In this context, "host-initiated" write means written by KVM userspace
> with ioctl(KVM_SET_MSR).  It generally happens only on VM startup, reset
> or live migration.

To be clear, the target of the write is still the vCPU's emulated MSR.

Paolo

  reply	other threads:[~2018-02-26 12:18 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
2018-02-26 12:16                       ` Paolo Bonzini
2018-02-26 12:18                         ` Paolo Bonzini [this message]
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

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=3866d359-0ef8-6a99-6254-84890be62b93@redhat.com \
    --to=pbonzini@redhat.com \
    --cc=bp@alien8.de \
    --cc=kernellwp@gmail.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=rkrcmar@redhat.com \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.