Jan,
Any comments? I feel some confused about your point 'disable cpuid feature for older machine types by default': are you planning a common approach for this common issue, or, you just ask me a specific solution for the tsc deadline timer case?
Thanks,
Jinsong
Liu, Jinsong wrote:
>> My point is that
>>
>> qemu-version-A [-cpu whatever]
>>
>> should provide the same VM as
>>
>> qemu-version-B -machine pc-A [-cpu whatever]
>>
>> specifically if you leave out the cpu specification.
>>
>> So the compat machine could establish a feature mask (e.g. append
>> some "-tsc_deadline" in this case). But, indeed, we need a new
>> channel for this.
>>
>
> Yes, if such requirement need to be satisfied, I agree we need a new
> channel to solve this kind of common issue.
>
> As for tsc deadline timer feature exposing, I write an updated patch
> as attached. 1). It exposes tsc deadline timer feature to guest if
> in-kernel irqchip is used and kvm has emulated tsc deadline timer;
> 2). It also authorizes user to control the feature exposing via a cpu
> feature flag;
>
> Thanks,
> Jinsong
>
> ====================
> From 5b7d5f459b621686e78e437010ce34748bcb9e8e Mon Sep 17 00:00:00 2001
> From: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
> Date: Wed, 29 Feb 2012 01:53:15 +0800
> Subject: [PATCH] Expose tsc deadline timer feature to guest
>
> It exposes tsc deadline timer feature to guest if in-kernel irqchip
> is used
> and kvm has emulated tsc deadline timer.
> It also authorizes user to control the feature exposing via a cpu
> feature flag.
>
> Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
> ---
> target-i386/cpu.h | 1 +
> target-i386/cpuid.c | 2 +-
> target-i386/kvm.c | 4 ++++
> 3 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/target-i386/cpu.h b/target-i386/cpu.h
> index d92be5d..3409afe 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/cpuid.c b/target-i386/cpuid.c
> index b9bfeaf..ac4b79c 100644
> --- a/target-i386/cpuid.c
> +++ b/target-i386/cpuid.c
> @@ -50,7 +50,7 @@ static const char *ext_feature_name[] = {
> "fma", "cx16", "xtpr", "pdcm",
> NULL, NULL, "dca", "sse4.1|sse4_1",
> "sse4.2|sse4_2", "x2apic", "movbe", "popcnt",
> - NULL, "aes", "xsave", "osxsave",
> + "tsc_deadline", "aes", "xsave", "osxsave",
> "avx", NULL, NULL, "hypervisor",
> };
> static const char *ext2_feature_name[] = {
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 7079e87..2639699 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -370,6 +370,10 @@ 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;
> + if (!kvm_irqchip_in_kernel() ||
> + !kvm_check_extension(s, KVM_CAP_TSC_DEADLINE_TIMER)) {
> + env->cpuid_ext_features &= ~CPUID_EXT_TSC_DEADLINE_TIMER;
> + }
>
> env->cpuid_ext2_features &= kvm_arch_get_supported_cpuid(s,
>
> 0x80000001, 0, R_EDX);
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