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Message-ID: <20140708151542.GF1688@ERROL.INI.CMU.EDU>
Date: Tue, 8 Jul 2014 11:15:43 -0400
From: "Gabriel L. Somlo" <gsomlo@...il.com>
To: KVM <kvm@...r.kernel.org>
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
Gleb Natapov <gleb@...nel.org>,
Eric Northup <digitaleric@...gle.com>,
Nadav Amit <namit@...technion.ac.il>,
Paolo Bonzini <pbonzini@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
the arch/x86 maintainers <x86@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
nadav.amit@...il.com, joro@...tes.org, agraf@...e.de
Subject: Ping: Re: [PATCH] Revert "kvm: x86: emulate monitor and mwait
instructions as nop"
Any decision on this ? If we're going to revert monitor/mwait as nop,
it's hopefully not too late to avoid having it show up in an official
(3.16 ?) kernel release...
Thanks,
--Gabriel
On Thu, Jun 19, 2014 at 09:59:35AM -0400, Gabriel L. Somlo wrote:
> This reverts commit 87c00572ba05aa8c9db118da75c608f47eb10b9e.
>
> OS X <= 10.7.* are the only known guests which realistically required
> this functionality. As it turns out, OS X can be told to forego using
> monitor/mwait by passing it "idlehalt=0" as a kernel argument, so we're
> better off removing this hack from KVM altogether, at least for now.
>
> Signed-off-by: Gabriel L. Somlo <somlo@....edu>
> Acked-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>
> OK, here's the formal proposal to revert my original monitor/mwait hack...
> I wish I knew about the "idlehalt=0" before I submitted it, but such is life.
> Depending on how those of you higher up the food chain feel, I can tolerate
> leaving the hack in if it's never on by default (i.e. no CPUID advertisement),
> but would feel better if we could simply undo this until we have a better
> solution, something less controversial...
>
> Thanks, and sorry for all the noise,
> Gabriel
>
> arch/x86/kvm/cpuid.c | 2 --
> arch/x86/kvm/svm.c | 28 ++++++++--------------------
> arch/x86/kvm/vmx.c | 20 ++++----------------
> 3 files changed, 12 insertions(+), 38 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 38a0afe..17b42fa 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -283,8 +283,6 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> 0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW);
> /* cpuid 1.ecx */
> const u32 kvm_supported_word4_x86_features =
> - /* NOTE: MONITOR (and MWAIT) are emulated as NOP,
> - * but *not* advertised to guests via CPUID ! */
> F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ |
> 0 /* DS-CPL, VMX, SMX, EST */ |
> 0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ |
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index ec8366c..6b88b6a 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2763,6 +2763,12 @@ static int xsetbv_interception(struct vcpu_svm *svm)
> return 1;
> }
>
> +static int invalid_op_interception(struct vcpu_svm *svm)
> +{
> + kvm_queue_exception(&svm->vcpu, UD_VECTOR);
> + return 1;
> +}
> +
> static int task_switch_interception(struct vcpu_svm *svm)
> {
> u16 tss_selector;
> @@ -3274,24 +3280,6 @@ static int pause_interception(struct vcpu_svm *svm)
> return 1;
> }
>
> -static int nop_interception(struct vcpu_svm *svm)
> -{
> - skip_emulated_instruction(&(svm->vcpu));
> - return 1;
> -}
> -
> -static int monitor_interception(struct vcpu_svm *svm)
> -{
> - printk_once(KERN_WARNING "kvm: MONITOR instruction emulated as NOP!\n");
> - return nop_interception(svm);
> -}
> -
> -static int mwait_interception(struct vcpu_svm *svm)
> -{
> - printk_once(KERN_WARNING "kvm: MWAIT instruction emulated as NOP!\n");
> - return nop_interception(svm);
> -}
> -
> static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
> [SVM_EXIT_READ_CR0] = cr_interception,
> [SVM_EXIT_READ_CR3] = cr_interception,
> @@ -3349,8 +3337,8 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
> [SVM_EXIT_CLGI] = clgi_interception,
> [SVM_EXIT_SKINIT] = skinit_interception,
> [SVM_EXIT_WBINVD] = emulate_on_interception,
> - [SVM_EXIT_MONITOR] = monitor_interception,
> - [SVM_EXIT_MWAIT] = mwait_interception,
> + [SVM_EXIT_MONITOR] = invalid_op_interception,
> + [SVM_EXIT_MWAIT] = invalid_op_interception,
> [SVM_EXIT_XSETBV] = xsetbv_interception,
> [SVM_EXIT_NPF] = pf_interception,
> };
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 801332e..163958f 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5672,24 +5672,12 @@ static int handle_pause(struct kvm_vcpu *vcpu)
> return 1;
> }
>
> -static int handle_nop(struct kvm_vcpu *vcpu)
> +static int handle_invalid_op(struct kvm_vcpu *vcpu)
> {
> - skip_emulated_instruction(vcpu);
> + kvm_queue_exception(vcpu, UD_VECTOR);
> return 1;
> }
>
> -static int handle_mwait(struct kvm_vcpu *vcpu)
> -{
> - printk_once(KERN_WARNING "kvm: MWAIT instruction emulated as NOP!\n");
> - return handle_nop(vcpu);
> -}
> -
> -static int handle_monitor(struct kvm_vcpu *vcpu)
> -{
> - printk_once(KERN_WARNING "kvm: MONITOR instruction emulated as NOP!\n");
> - return handle_nop(vcpu);
> -}
> -
> /*
> * To run an L2 guest, we need a vmcs02 based on the L1-specified vmcs12.
> * We could reuse a single VMCS for all the L2 guests, but we also want the
> @@ -6651,8 +6639,8 @@ static int (*const kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
> [EXIT_REASON_EPT_VIOLATION] = handle_ept_violation,
> [EXIT_REASON_EPT_MISCONFIG] = handle_ept_misconfig,
> [EXIT_REASON_PAUSE_INSTRUCTION] = handle_pause,
> - [EXIT_REASON_MWAIT_INSTRUCTION] = handle_mwait,
> - [EXIT_REASON_MONITOR_INSTRUCTION] = handle_monitor,
> + [EXIT_REASON_MWAIT_INSTRUCTION] = handle_invalid_op,
> + [EXIT_REASON_MONITOR_INSTRUCTION] = handle_invalid_op,
> [EXIT_REASON_INVEPT] = handle_invept,
> };
>
> --
> 1.9.3
>
--
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