Re: [Qemu-devel] [PATCH] Expose tsc deadline timer cpuid to guest

[Jan Kiszka]

On 2011-12-26 21:49, Liu, Jinsong wrote:
> From 19caf1db1f93e6f6b736e1dfd5e91a0c7669adec Mon Sep 17 00:00:00 2001
> From: Liu Jinsong <address@hidden>
> Date: Tue, 27 Dec 2011 04:08:27 +0800
> Subject: [PATCH] Expose tsc deadline timer cpuid to guest
> 
> Depend on several factors:
> 1. Considering live migration, user enable/disable tsc deadline timer;
> 2. If guest use kvm apic and kvm emulate tsc deadline timer, expose it;
> 3. If in the future qemu support tsc deadline timer emulation,
>    and guest use qemu apic, add cpuid exposing case then.
> 
> Signed-off-by: Liu, Jinsong <address@hidden>
> ---
>  linux-headers/linux/kvm.h |    1 +
>  qemu-kvm.h                |    1 +
>  qemu-options.hx           |    3 +++
>  target-i386/cpu.h         |    1 +
>  target-i386/kvm.c         |   12 ++++++++++++
>  vl.c                      |    4 ++++
>  6 files changed, 22 insertions(+), 0 deletions(-)
> 
> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
> index a8761d3..1d3a4f4 100644
> --- a/linux-headers/linux/kvm.h
> +++ b/linux-headers/linux/kvm.h
> @@ -558,6 +558,7 @@ struct kvm_ppc_pvinfo {
>  #define KVM_CAP_PPC_PAPR 68
>  #define KVM_CAP_SW_TLB 69
>  #define KVM_CAP_ONE_REG 70
> +#define KVM_CAP_TSC_DEADLINE_TIMER 72
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  

Please split linux-header update from functional changes (then the
former should just be the outcome of a update-linux-headers.sh run).

> diff --git a/qemu-kvm.h b/qemu-kvm.h
> index 2bd5602..8c6c2ea 100644
> --- a/qemu-kvm.h
> +++ b/qemu-kvm.h
> @@ -260,6 +260,7 @@ extern int kvm_irqchip;
>  extern int kvm_pit;
>  extern int kvm_pit_reinject;
>  extern unsigned int kvm_shadow_memory;
> +extern int tsc_deadline_timer;
>  
>  int kvm_handle_tpr_access(CPUState *env);
>  void kvm_tpr_enable_vapic(CPUState *env);
> diff --git a/qemu-options.hx b/qemu-options.hx
> index f6df6b9..eff6644 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -2619,6 +2619,9 @@ DEF("no-kvm-pit-reinjection", 0, 
> QEMU_OPTION_no_kvm_pit_reinjection,
>      "-no-kvm-pit-reinjection\n"
>      "                disable KVM kernel mode PIT interrupt reinjection\n",
>      QEMU_ARCH_I386)
> +DEF("no-tsc-deadline-timer", 0, QEMU_OPTION_no_tsc_deadline_timer,
> +    "-no-tsc-deadline-timer     disable tsc deadline timer\n",
> +    QEMU_ARCH_I386)

Hmm, I would really prefer to stop adding switches like this. They won't
make it upstream anyway.

Can't this control be attached to legacy qemu machine models, ie. here
anything <= pc-1.0? See how we handle kvmclock.

>  DEF("tdf", 0, QEMU_OPTION_tdf,
>      "-tdf            enable guest time drift compensation\n", QEMU_ARCH_ALL)
>  DEF("kvm-shadow-memory", HAS_ARG, QEMU_OPTION_kvm_shadow_memory,
> diff --git a/target-i386/cpu.h b/target-i386/cpu.h
> index 177d8aa..767d2eb 100644
> --- a/target-i386/cpu.h
> +++ b/target-i386/cpu.h
> @@ -399,6 +399,7 @@
>  #define CPUID_EXT_X2APIC   (1 << 21)
>  #define CPUID_EXT_MOVBE    (1 << 22)
>  #define CPUID_EXT_POPCNT   (1 << 23)
> +#define CPUID_EXT_TSC_DEADLINE_TIMER (1 << 24)
>  #define CPUID_EXT_XSAVE    (1 << 26)
>  #define CPUID_EXT_OSXSAVE  (1 << 27)
>  #define CPUID_EXT_HYPERVISOR  (1 << 31)
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index d50de90..740184d 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -370,6 +370,18 @@ int kvm_arch_init_vcpu(CPUState *env)
>      i = env->cpuid_ext_features & CPUID_EXT_HYPERVISOR;
>      env->cpuid_ext_features &= kvm_arch_get_supported_cpuid(s, 1, 0, R_ECX);
>      env->cpuid_ext_features |= i;
> +    /*
> +     * 1. Considering live migration, user enable/disable tsc deadline timer;
> +     * 2. If guest use kvm apic and kvm emulate tsc deadline timer, expose 
> it;
> +     * 3. If in the future qemu support tsc deadline timer emulation,
> +     *    and guest use qemu apic, add cpuid exposing case then.
> +     */
> +    env->cpuid_ext_features &= ~CPUID_EXT_TSC_DEADLINE_TIMER;
> +    if (tsc_deadline_timer) {
> +        if (kvm_irqchip_in_kernel() &&
> +            kvm_check_extension(s, KVM_CAP_TSC_DEADLINE_TIMER))
> +            env->cpuid_ext_features |= CPUID_EXT_TSC_DEADLINE_TIMER;
> +    }

Please mind the coding style.

Jan

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