From: Marcelo Tosatti <mtosatti@redhat.com>
To: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Luiz Capitulino <lcapitulino@redhat.com>
Subject: Re: [RFC PATCH 0/2] kvmclock: fix ABI breakage from PVCLOCK_COUNTS_FROM_ZERO.
Date: Mon, 21 Sep 2015 21:40:19 -0300 [thread overview]
Message-ID: <20150922004019.GA25115@amt.cnet> (raw)
In-Reply-To: <20150921223713.GA21139@amt.cnet>
> So either:
>
> Proceed with guest solution:
> -> Make sure the overflow can't happen (and write down why not in the
> code). Don't assume a small delta between kvmclock values of vcpus.
> -> Handle stable -> non-stable kvmclock transition.
> -> kvmclock counts from zero should not depend on stable kvmclock
> (because nohz_full should work on hpet host systems).
>
> Enable counts-from-zero on MSR_KVM_SYSTEM_TIME_NEW:
> -> Figure out whats wrong with different kvmclock values on hotplug,
> and fix it.
Find data which allows you to differentiate between hotplug of pCPU-0
and system initialization.
Easy one: whether MSR_KVM_SYSTEM_TIME_NEW contains valid data (that is
kvmclock is enabled) for vCPUs other than vCPU-0.
This can't be the case on system initialization (otherwise the host will
be corrupting guest memory), and must be the case when hotplugging
vCPU-0.
next prev parent reply other threads:[~2015-09-22 0:40 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-18 15:54 [RFC PATCH 0/2] kvmclock: fix ABI breakage from PVCLOCK_COUNTS_FROM_ZERO Radim Krčmář
2015-09-18 15:54 ` [PATCH 1/2] x86: kvmclock: abolish PVCLOCK_COUNTS_FROM_ZERO Radim Krčmář
2015-09-22 19:01 ` Marcelo Tosatti
2015-09-28 14:10 ` Paolo Bonzini
2015-09-18 15:54 ` [PATCH 2/2] Revert "KVM: x86: zero kvmclock_offset when vcpu0 initializes kvmclock system MSR" Radim Krčmář
2015-09-22 19:01 ` Marcelo Tosatti
2015-09-22 19:52 ` Paolo Bonzini
2015-09-22 20:23 ` Marcelo Tosatti
2015-09-20 22:57 ` [RFC PATCH 0/2] kvmclock: fix ABI breakage from PVCLOCK_COUNTS_FROM_ZERO Marcelo Tosatti
2015-09-21 15:12 ` Radim Krčmář
2015-09-21 15:43 ` Radim Krčmář
2015-09-21 15:52 ` Marcelo Tosatti
2015-09-21 20:00 ` Radim Krčmář
2015-09-21 20:53 ` Marcelo Tosatti
2015-09-21 22:00 ` Radim Krčmář
2015-09-21 22:37 ` Marcelo Tosatti
2015-09-22 0:40 ` Marcelo Tosatti [this message]
2015-09-22 14:33 ` Radim Krčmář
2015-09-22 14:46 ` Radim Krčmář
2015-09-28 11:05 ` Paolo Bonzini
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