From: Paolo Bonzini <pbonzini@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Jingqi Liu <jingqi.liu@intel.com>,
rkrcmar@redhat.com, mingo@redhat.com, hpa@zytor.com,
x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, wei.w.wang@intel.com,
Robert Hoo <robert.hu@linux.intel.com>
Subject: Re: [PATCH v2] KVM: Expose the split lock detection feature to guest VM
Date: Wed, 4 Jul 2018 18:21:01 +0200 [thread overview]
Message-ID: <a83b9b41-afbb-016d-528b-029f1b6228ae@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1807041636340.1752@nanos.tec.linutronix.de>
On 04/07/2018 16:51, Thomas Gleixner wrote:
> There is no rush for this to be in KVM/QEMU now because all what exists for
> this new split lock thing is 'silicon' running on an emulator. And w/o
> support in the kernel proper this is completely useless.
That's good. I assumed it was IceLake, in which case the feature would
block the definition of a standard IceLake CPU model in QEMU.
> So this needs the following things:
>
> 1) Proper enumeration via CPUID or MISC_FEATURES. The current detection
> hack is just broken.
Yes please.
> 2) A proper host side implementation, which then automatically makes the
> stuff usable in a guest once it is exposed.
If the CPUID bit or MISC_FEATURES is added, you don't even need the host
side for the guests to use it. It's only needed now because of the ugly
MSR-based detection.
> 3) A proper way how to expose MSR_TEST_CTL to the guest, but surely not
> with extra split_lock_ctrl voodoo. It's an MSR nothing else. KVM/QEMU
> have standartized ways to deal with MSRs and the required selective
> bitwise access control.
That part is pretty much standard, I'm not worried about it. We have
one variable in struct kvm_vcpu_arch for each MSR (or set of MSRs) that
we expose, so that's the split_lock_ctrl voodoo. :)
Once the detection is sorted out, KVM is easy.
Paolo
next prev parent reply other threads:[~2018-07-04 16:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-04 13:06 [PATCH v2] KVM: Expose the split lock detection feature to guest VM Jingqi Liu
2018-07-04 13:36 ` Paolo Bonzini
2018-07-04 14:51 ` Thomas Gleixner
2018-07-04 16:21 ` Paolo Bonzini [this message]
2018-07-04 18:39 ` Thomas Gleixner
2018-07-06 8:13 ` Liu, Jingqi
2018-07-04 23:07 ` kbuild test robot
2018-07-04 23:07 ` kbuild test robot
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