From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <kernellwp@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Haiwei Li <lihaiwei@tencent.com>
Subject: Re: [PATCH v2] KVM: X86: Ultra fast single target IPI fastpath
Date: Fri, 10 Apr 2020 17:50:35 +0200 [thread overview]
Message-ID: <f51251cc-885e-2f7a-b18d-faa76db15b87@redhat.com> (raw)
In-Reply-To: <20200410153539.GD22482@linux.intel.com>
On 10/04/20 17:35, Sean Christopherson wrote:
> IMO, this should come at the very end of vmx_vcpu_run(). At a minimum, it
> needs to be moved below the #MC handling and below
>
> if (vmx->fail || (vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
> return;
Why? It cannot run in any of those cases, since the vmx->exit_reason
won't match.
> KVM more or less assumes vmx->idt_vectoring_info is always valid, and it's
> not obvious that a generic fastpath call can safely run before
> vmx_complete_interrupts(), e.g. the kvm_clear_interrupt_queue() call.
Not KVM, rather vmx.c. You're right about a generic fastpath, but in
this case kvm_irq_delivery_to_apic_fast is not touching VMX state; even
if you have a self-IPI, the modification of vCPU state is only scheduled
here and will happen later via either kvm_x86_ops.sync_pir_to_irr or
KVM_REQ_EVENT.
Paolo
next prev parent reply other threads:[~2020-04-10 15:50 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-10 1:03 Wanpeng Li
2020-04-10 15:17 ` Paolo Bonzini
2020-04-13 1:43 ` Wanpeng Li
2020-04-10 15:35 ` Sean Christopherson
2020-04-10 15:50 ` Paolo Bonzini [this message]
2020-04-10 17:47 ` Sean Christopherson
2020-04-10 17:47 ` [PATCH v3 1/2] KVM: VMX: Optimize handling of VM-Entry failures in vmx_vcpu_run() Sean Christopherson
2020-04-10 17:47 ` [PATCH v3 2/2] KVM: X86: Ultra fast single target IPI fastpath Sean Christopherson
2020-04-10 18:43 ` [PATCH v2] " Paolo Bonzini
2020-04-11 0:34 ` Wanpeng Li
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