From: Paolo Bonzini <pbonzini@redhat.com>
To: Andrea Arcangeli <aarcange@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: [PATCH 11/13] KVM: retpolines: x86: eliminate retpoline from vmx.c exit handlers
Date: Tue, 5 Nov 2019 11:20:42 +0100 [thread overview]
Message-ID: <9a7d3134-b8eb-dfae-9c26-c21d3c1a1ea8@redhat.com> (raw)
In-Reply-To: <20191104230001.27774-12-aarcange@redhat.com>
On 04/11/19 23:59, Andrea Arcangeli wrote:
> It's enough to check the exit value and issue a direct call to avoid
> the retpoline for all the common vmexit reasons.
>
> Of course CONFIG_RETPOLINE already forbids gcc to use indirect jumps
> while compiling all switch() statements, however switch() would still
> allow the compiler to bisect the case value. It's more efficient to
> prioritize the most frequent vmexits instead.
>
> The halt may be slow paths from the point of the guest, but not
> necessarily so from the point of the host if the host runs at full CPU
> capacity and no host CPU is ever left idle.
>
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 18 ++++++++++++++++--
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index a6afa5f4a01c..582f837dc8c2 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -5905,9 +5905,23 @@ int kvm_x86_handle_exit(struct kvm_vcpu *vcpu)
> }
>
> if (exit_reason < kvm_vmx_max_exit_handlers
> - && kvm_vmx_exit_handlers[exit_reason])
> + && kvm_vmx_exit_handlers[exit_reason]) {
> +#ifdef CONFIG_RETPOLINE
> + if (exit_reason == EXIT_REASON_MSR_WRITE)
> + return kvm_emulate_wrmsr(vcpu);
> + else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER)
> + return handle_preemption_timer(vcpu);
> + else if (exit_reason == EXIT_REASON_PENDING_INTERRUPT)
> + return handle_interrupt_window(vcpu);
> + else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
> + return handle_external_interrupt(vcpu);
> + else if (exit_reason == EXIT_REASON_HLT)
> + return kvm_emulate_halt(vcpu);
> + else if (exit_reason == EXIT_REASON_EPT_MISCONFIG)
> + return handle_ept_misconfig(vcpu);
> +#endif
> return kvm_vmx_exit_handlers[exit_reason](vcpu);
> - else {
> + } else {
> vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n",
> exit_reason);
> dump_vmcs();
>
Queued, thanks.
Paolo
next prev parent reply other threads:[~2019-11-05 10:22 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-04 22:59 [PATCH 00/13] KVM monolithic v3 Andrea Arcangeli
2019-11-04 22:59 ` [PATCH 01/13] KVM: monolithic: x86: remove kvm.ko Andrea Arcangeli
2019-11-04 22:59 ` [PATCH 02/13] KVM: monolithic: x86: convert the kvm_x86_ops and kvm_pmu_ops methods to external functions Andrea Arcangeli
2019-11-04 22:59 ` [PATCH 03/13] kvm: monolithic: fixup x86-32 build Andrea Arcangeli
2019-11-05 10:04 ` Paolo Bonzini
2019-11-05 10:37 ` Paolo Bonzini
2019-11-05 13:54 ` Andrea Arcangeli
2019-11-05 14:09 ` Paolo Bonzini
2019-11-05 14:56 ` Andrea Arcangeli
2019-11-05 15:10 ` Paolo Bonzini
2019-11-08 13:56 ` Jessica Yu
2019-11-08 19:51 ` Paolo Bonzini
2019-11-08 20:01 ` Andrea Arcangeli
2019-11-08 21:02 ` Paolo Bonzini
2019-11-08 21:26 ` Andrea Arcangeli
2019-11-08 23:10 ` Paolo Bonzini
2019-11-09 3:30 ` Masahiro Yamada
2019-11-04 22:59 ` [PATCH 04/13] KVM: monolithic: x86: handle the request_immediate_exit variation Andrea Arcangeli
2019-11-04 22:59 ` [PATCH 05/13] KVM: monolithic: add more section prefixes Andrea Arcangeli
2019-11-05 10:16 ` Paolo Bonzini
2019-11-04 22:59 ` [PATCH 06/13] KVM: monolithic: x86: remove __exit section prefix from machine_unsetup Andrea Arcangeli
2019-11-05 10:16 ` Paolo Bonzini
2019-11-04 22:59 ` [PATCH 07/13] KVM: monolithic: x86: remove __init section prefix from kvm_x86_cpu_has_kvm_support Andrea Arcangeli
2019-11-05 10:16 ` Paolo Bonzini
2019-11-04 22:59 ` [PATCH 08/13] KVM: monolithic: remove exports Andrea Arcangeli
2019-11-04 22:59 ` [PATCH 09/13] KVM: monolithic: x86: drop the kvm_pmu_ops structure Andrea Arcangeli
2019-11-04 22:59 ` [PATCH 10/13] KVM: x86: optimize more exit handlers in vmx.c Andrea Arcangeli
2019-11-05 10:20 ` Paolo Bonzini
2019-11-04 22:59 ` [PATCH 11/13] KVM: retpolines: x86: eliminate retpoline from vmx.c exit handlers Andrea Arcangeli
2019-11-05 10:20 ` Paolo Bonzini [this message]
2019-11-04 23:00 ` [PATCH 12/13] KVM: retpolines: x86: eliminate retpoline from svm.c " Andrea Arcangeli
2019-11-05 10:21 ` Paolo Bonzini
2019-11-04 23:00 ` [PATCH 13/13] x86: retpolines: eliminate retpoline from msr event handlers Andrea Arcangeli
2019-11-05 10:21 ` Paolo Bonzini
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