From: Eduardo Habkost <ehabkost@redhat.com>
To: Tao Xu <tao3.xu@intel.com>
Cc: pbonzini@redhat.com, rkrcmar@redhat.com, corbet@lwn.net,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, sean.j.christopherson@intel.com,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
fenghua.yu@intel.com, xiaoyao.li@linux.intel.com,
jingqi.liu@intel.com
Subject: Re: [PATCH v7 2/3] KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL
Date: Tue, 16 Jul 2019 13:03:58 -0300 [thread overview]
Message-ID: <20190716160358.GE26800@habkost.net> (raw)
In-Reply-To: <20190712082907.29137-3-tao3.xu@intel.com>
On Fri, Jul 12, 2019 at 04:29:06PM +0800, Tao Xu wrote:
> UMWAIT and TPAUSE instructions use IA32_UMWAIT_CONTROL at MSR index E1H
> to determines the maximum time in TSC-quanta that the processor can reside
> in either C0.1 or C0.2.
>
> This patch emulates MSR IA32_UMWAIT_CONTROL in guest and differentiate
> IA32_UMWAIT_CONTROL between host and guest. The variable
> mwait_control_cached in arch/x86/power/umwait.c caches the MSR value, so
> this patch uses it to avoid frequently rdmsr of IA32_UMWAIT_CONTROL.
>
> Co-developed-by: Jingqi Liu <jingqi.liu@intel.com>
> Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
> Signed-off-by: Tao Xu <tao3.xu@intel.com>
> ---
[...]
> +static void atomic_switch_umwait_control_msr(struct vcpu_vmx *vmx)
> +{
> + if (!vmx_has_waitpkg(vmx))
> + return;
> +
> + if (vmx->msr_ia32_umwait_control != umwait_control_cached)
> + add_atomic_switch_msr(vmx, MSR_IA32_UMWAIT_CONTROL,
> + vmx->msr_ia32_umwait_control,
> + umwait_control_cached, false);
How exactly do we ensure NR_AUTOLOAD_MSRS (8) is still large enough?
I see 3 existing add_atomic_switch_msr() calls, but the one at
atomic_switch_perf_msrs() is in a loop. Are we absolutely sure
that perf_guest_get_msrs() will never return more than 5 MSRs?
> + else
> + clear_atomic_switch_msr(vmx, MSR_IA32_UMWAIT_CONTROL);
> +}
> +
> static void vmx_arm_hv_timer(struct vcpu_vmx *vmx, u32 val)
> {
> vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, val);
[...]
--
Eduardo
next prev parent reply other threads:[~2019-07-16 16:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-12 8:29 [PATCH v7 0/3] KVM: x86: Enable user wait instructions Tao Xu
2019-07-12 8:29 ` [PATCH v7 1/3] KVM: x86: add support for " Tao Xu
2019-07-12 15:13 ` Sean Christopherson
2019-07-15 1:11 ` Tao Xu
2019-07-12 8:29 ` [PATCH v7 2/3] KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL Tao Xu
2019-07-12 15:52 ` Sean Christopherson
2019-07-15 1:22 ` Tao Xu
2019-07-15 14:16 ` Sean Christopherson
2019-07-16 16:03 ` Eduardo Habkost [this message]
2019-07-17 1:17 ` Tao Xu
2019-07-17 2:03 ` Tao Xu
2019-07-12 8:29 ` [PATCH v7 3/3] KVM: vmx: handle vm-exit for UMWAIT and TPAUSE Tao Xu
2019-07-12 16:03 ` Sean Christopherson
2019-07-13 14:22 ` Tao Xu
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