* [PATCH] x86: kvm Require const tsc for RT
@ 2022-03-01 17:55 Sebastian Andrzej Siewior
2022-03-01 17:57 ` Paolo Bonzini
2022-03-14 9:28 ` Sebastian Andrzej Siewior
0 siblings, 2 replies; 4+ messages in thread
From: Sebastian Andrzej Siewior @ 2022-03-01 17:55 UTC (permalink / raw)
To: kvm, x86
Cc: Borislav Petkov, Dave Hansen, H. Peter Anvin, Ingo Molnar,
Jim Mattson, Joerg Roedel, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Vitaly Kuznetsov, Wanpeng Li
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 6 Nov 2011 12:26:18 +0100
Non constant TSC is a nightmare on bare metal already, but with
virtualization it becomes a complete disaster because the workarounds
are horrible latency wise. That's also a preliminary for running RT in
a guest on top of a RT host.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/x86/kvm/x86.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 82a9dcd8c67fe..54d2090d04e7a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8826,6 +8826,12 @@ int kvm_arch_init(void *opaque)
goto out;
}
+ if (IS_ENABLED(CONFIG_PREEMPT_RT) && !boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
+ pr_err("RT requires X86_FEATURE_CONSTANT_TSC\n");
+ r = -EOPNOTSUPP;
+ goto out;
+ }
+
r = -ENOMEM;
x86_emulator_cache = kvm_alloc_emulator_cache();
--
2.35.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] x86: kvm Require const tsc for RT
2022-03-01 17:55 [PATCH] x86: kvm Require const tsc for RT Sebastian Andrzej Siewior
@ 2022-03-01 17:57 ` Paolo Bonzini
2022-03-14 9:28 ` Sebastian Andrzej Siewior
1 sibling, 0 replies; 4+ messages in thread
From: Paolo Bonzini @ 2022-03-01 17:57 UTC (permalink / raw)
To: Sebastian Andrzej Siewior, kvm, x86
Cc: Borislav Petkov, Dave Hansen, H. Peter Anvin, Ingo Molnar,
Jim Mattson, Joerg Roedel, Sean Christopherson, Thomas Gleixner,
Vitaly Kuznetsov, Wanpeng Li
On 3/1/22 18:55, Sebastian Andrzej Siewior wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
> Date: Sun, 6 Nov 2011 12:26:18 +0100
>
> Non constant TSC is a nightmare on bare metal already, but with
> virtualization it becomes a complete disaster because the workarounds
> are horrible latency wise. That's also a preliminary for running RT in
> a guest on top of a RT host.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> arch/x86/kvm/x86.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 82a9dcd8c67fe..54d2090d04e7a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8826,6 +8826,12 @@ int kvm_arch_init(void *opaque)
> goto out;
> }
>
> + if (IS_ENABLED(CONFIG_PREEMPT_RT) && !boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
> + pr_err("RT requires X86_FEATURE_CONSTANT_TSC\n");
> + r = -EOPNOTSUPP;
> + goto out;
> + }
> +
> r = -ENOMEM;
>
> x86_emulator_cache = kvm_alloc_emulator_cache();
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Thanks,
Paolo
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] x86: kvm Require const tsc for RT
2022-03-01 17:55 [PATCH] x86: kvm Require const tsc for RT Sebastian Andrzej Siewior
2022-03-01 17:57 ` Paolo Bonzini
@ 2022-03-14 9:28 ` Sebastian Andrzej Siewior
2022-03-15 21:07 ` Paolo Bonzini
1 sibling, 1 reply; 4+ messages in thread
From: Sebastian Andrzej Siewior @ 2022-03-14 9:28 UTC (permalink / raw)
To: kvm, x86
Cc: Borislav Petkov, Dave Hansen, H. Peter Anvin, Ingo Molnar,
Jim Mattson, Joerg Roedel, Paolo Bonzini, Sean Christopherson,
Thomas Gleixner, Vitaly Kuznetsov, Wanpeng Li
On 2022-03-01 18:55:51 [+0100], To kvm@vger.kernel.org wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
> Date: Sun, 6 Nov 2011 12:26:18 +0100
>
> Non constant TSC is a nightmare on bare metal already, but with
> virtualization it becomes a complete disaster because the workarounds
> are horrible latency wise. That's also a preliminary for running RT in
> a guest on top of a RT host.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
ping.
> ---
> arch/x86/kvm/x86.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 82a9dcd8c67fe..54d2090d04e7a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8826,6 +8826,12 @@ int kvm_arch_init(void *opaque)
> goto out;
> }
>
> + if (IS_ENABLED(CONFIG_PREEMPT_RT) && !boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
> + pr_err("RT requires X86_FEATURE_CONSTANT_TSC\n");
> + r = -EOPNOTSUPP;
> + goto out;
> + }
> +
> r = -ENOMEM;
>
> x86_emulator_cache = kvm_alloc_emulator_cache();
> --
> 2.35.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] x86: kvm Require const tsc for RT
2022-03-14 9:28 ` Sebastian Andrzej Siewior
@ 2022-03-15 21:07 ` Paolo Bonzini
0 siblings, 0 replies; 4+ messages in thread
From: Paolo Bonzini @ 2022-03-15 21:07 UTC (permalink / raw)
To: Sebastian Andrzej Siewior, kvm, x86
Cc: Borislav Petkov, Dave Hansen, H. Peter Anvin, Ingo Molnar,
Jim Mattson, Joerg Roedel, Sean Christopherson, Thomas Gleixner,
Vitaly Kuznetsov, Wanpeng Li
On 3/14/22 10:28, Sebastian Andrzej Siewior wrote:
> On 2022-03-01 18:55:51 [+0100], To kvm@vger.kernel.org wrote:
>> From: Thomas Gleixner <tglx@linutronix.de>
>> Date: Sun, 6 Nov 2011 12:26:18 +0100
>>
>> Non constant TSC is a nightmare on bare metal already, but with
>> virtualization it becomes a complete disaster because the workarounds
>> are horrible latency wise. That's also a preliminary for running RT in
>> a guest on top of a RT host.
>>
>> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>
> ping.
Queued, thanks.
Paolo
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-03-01 17:55 [PATCH] x86: kvm Require const tsc for RT Sebastian Andrzej Siewior
2022-03-01 17:57 ` Paolo Bonzini
2022-03-14 9:28 ` Sebastian Andrzej Siewior
2022-03-15 21:07 ` Paolo Bonzini
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