On Wed, Jun 18, 2014 at 02:46:01PM -0400, Gabriel L. Somlo wrote:
> On Wed, Jun 18, 2014 at 10:59:14AM -0700, Eric Northup wrote:
> > On Wed, Jun 18, 2014 at 7:19 AM, Nadav Amit <namit@xxxxxxxxxxxxxxxxx> wrote:
> > > mwait and monitor are currently handled as nop. Considering this behavior, they
> > > should still be handled correctly, i.e., check execution conditions and generate
> > > exceptions when required. mwait and monitor may also be executed in real-mode
> > > and are not handled in that case. This patch performs the emulation of
> > > monitor-mwait according to Intel SDM (other than checking whether interrupt can
> > > be used as a break event).
> > >
> > > Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
>
> How about this instead (details in the commit log below) ? Please let
> me know what you think, and if you'd prefer me to send it out as a
> separate patch rather than a reply to this thread.
>
> Thanks,
> --Gabriel
If there's an easy workaround, I'm inclined to agree.
We can always go back to Gabriel's patch (and then we'll need
Nadav's one too) but if we release a kernel with this
support it becomes an ABI and we can't go back.
So let's be careful here, and revert the hack for 3.16.
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
>
> >From 0375a0aceb54cdbc26a6c0e5b43c46324f830ec3 Mon Sep 17 00:00:00 2001
> From: "Gabriel L. Somlo" <somlo@xxxxxxx>
> Date: Wed, 18 Jun 2014 14:39:15 -0400
> Subject: [PATCH] kvm: x86: revert "emulate monitor and mwait instructions as nop"
>
> 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.
>
> Signed-off-by: Gabriel L. Somlo <somlo@xxxxxxx>
> ---
> arch/x86/kvm/cpuid.c | 2 --
> arch/x86/kvm/svm.c | 8 +++-----
> arch/x86/kvm/vmx.c | 10 ++++------
> 3 files changed, 7 insertions(+), 13 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..0e8ef20 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3274,7 +3274,7 @@ static int pause_interception(struct vcpu_svm *svm)
> return 1;
> }
>
> -static int nop_interception(struct vcpu_svm *svm)
> +static int invalid_op_interception(struct vcpu_svm *svm)
> {
> skip_emulated_instruction(&(svm->vcpu));
> return 1;
> @@ -3282,14 +3282,12 @@ static int nop_interception(struct vcpu_svm *svm)
>
> static int monitor_interception(struct vcpu_svm *svm)
> {
> - printk_once(KERN_WARNING "kvm: MONITOR instruction emulated as NOP!\n");
> - return nop_interception(svm);
> + return invalid_op_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);
> + return invalid_op_interception(svm);
> }
>
> static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 801332e..577c7df 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5672,22 +5672,20 @@ 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);
> + return handle_invalid_op(vcpu);
> }
>
> static int handle_monitor(struct kvm_vcpu *vcpu)
> {
> - printk_once(KERN_WARNING "kvm: MONITOR instruction emulated as NOP!\n");
> - return handle_nop(vcpu);
> + return handle_invalid_op(vcpu);
> }
>
> /*
> --
> 1.9.3
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