From: James Hogan <james.hogan@imgtec.com>
To: linux-mips@linux-mips.org
Cc: David Daney <ddaney.cavm@gmail.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Gleb Natapov <gleb@kernel.org>,
kvm@vger.kernel.org, Ralf Baechle <ralf@linux-mips.org>,
Sanjay Lal <sanjayl@kymasys.com>
Subject: Re: [PATCH 11/21] MIPS: KVM: Rewrite count/compare timer emulation
Date: Fri, 25 Apr 2014 22:05:42 +0100 [thread overview]
Message-ID: <1591723.zAIKIVVUH7@radagast> (raw)
In-Reply-To: <535A94A5.1040200@gmail.com>
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Hi David,
On Friday 25 April 2014 10:00:21 David Daney wrote:
> > + /* Frequency of timer in Hz */
> > + uint32_t count_hz;
>
> We are currently running with timer frequencies of over 2GHz, so the
> width of this variable is close to the limit.
Interesting. Do you have 64-bit Count/Compare registers or just accept that
you'll wrap after only 2 seconds? (it seems like a fairly short maximum idle
time, though perhaps not important in the grand scheme of things)
> Your follow-on patch exports this to user-space as part of the KVM ABI.
>
> I would suggest, at least for the user-space ABI, to make this a 64-bit
> wide value.
Yes, it's 64-bit wide in the userspace API, so it should be future proof.
Currently it refuses to accept a value higher than 1GHz for numerical reasons
though. If this same timer code is to be adapted for sleeping VZ guests too
with those sorts of timer frequencies then it makes sense to ensure it can
handle higher frequencies (since OTOH VZ doesn't give you control over the
guest timer frequency, just the offset).
It's not strictly required for T&E though so I don't think it should be a
blocking factor.
Thanks
James
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next prev parent reply other threads:[~2014-04-25 21:05 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-25 15:19 [PATCH 00/21] MIPS: KVM: Fixes and guest timer rewrite James Hogan
2014-04-25 15:19 ` [PATCH 01/21] MIPS: KVM: Allocate at least 16KB for exception handlers James Hogan
2014-04-25 15:19 ` [PATCH 02/21] MIPS: KVM: Use local_flush_icache_range to fix RI on XBurst James Hogan
2014-04-25 15:19 ` [PATCH 03/21] MIPS: KVM: Use tlb_write_random James Hogan
2014-04-25 15:19 ` [PATCH 04/21] MIPS: KVM: Fix CP0_EBASE KVM register id James Hogan
2014-04-25 16:36 ` David Daney
2014-04-25 19:22 ` James Hogan
2014-04-25 15:19 ` [PATCH 05/21] MIPS: KVM: Add CP0_EPC KVM register access James Hogan
2014-04-25 16:44 ` David Daney
2014-04-25 20:29 ` James Hogan
2014-04-25 21:45 ` David Daney
2014-04-25 15:19 ` [PATCH 06/21] MIPS: KVM: Move KVM_{GET,SET}_ONE_REG definitions into kvm_host.h James Hogan
2014-04-25 15:19 ` [PATCH 07/21] MIPS: KVM: Add CP0_Count/Compare KVM register access James Hogan
2014-04-25 15:19 ` [PATCH 08/21] MIPS: KVM: Deliver guest interrupts after local_irq_disable() James Hogan
2014-04-25 15:19 ` [PATCH 09/21] MIPS: KVM: Fix timer race modifying guest CP0_Cause James Hogan
2014-04-25 16:55 ` David Daney
2014-04-25 20:42 ` James Hogan
2014-04-25 15:19 ` [PATCH 10/21] MIPS: KVM: Migrate hrtimer to follow VCPU James Hogan
2014-04-25 15:19 ` [PATCH 11/21] MIPS: KVM: Rewrite count/compare timer emulation James Hogan
2014-04-25 17:00 ` David Daney
2014-04-25 21:05 ` James Hogan [this message]
2014-04-25 15:19 ` [PATCH 12/21] MIPS: KVM: Override guest kernel timer frequency directly James Hogan
2014-04-25 15:19 ` [PATCH 13/21] MIPS: KVM: Add master disable count interface James Hogan
2014-04-25 15:19 ` [PATCH 14/21] MIPS: KVM: Add nanosecond count bias KVM register James Hogan
2014-04-25 17:27 ` David Daney
2014-04-25 22:34 ` James Hogan
2014-04-26 9:37 ` Paolo Bonzini
2014-05-28 14:21 ` James Hogan
2014-05-28 16:24 ` Paolo Bonzini
2014-04-28 12:01 ` Paolo Bonzini
2014-04-28 15:17 ` James Hogan
2014-04-28 15:42 ` Paolo Bonzini
2014-04-25 15:19 ` [PATCH 15/21] MIPS: KVM: Add count frequency " James Hogan
2014-04-25 15:19 ` [PATCH 16/21] MIPS: KVM: Make kvm_mips_comparecount_{func,wakeup} static James Hogan
2014-04-25 15:20 ` [PATCH 17/21] MIPS: KVM: Whitespace fixes in kvm_mips_callbacks James Hogan
2014-04-25 15:20 ` [PATCH 18/21] MIPS: KVM: Fix kvm_debug bit-rottage James Hogan
2014-04-25 15:20 ` [PATCH 19/21] MIPS: KVM: Remove ifdef DEBUG around kvm_debug James Hogan
2014-04-25 15:20 ` [PATCH 20/21] MIPS: KVM: Quieten kvm_info() logging James Hogan
2014-04-25 15:20 ` [PATCH 21/21] MIPS: KVM: Remove redundant NULL checks before kfree() James Hogan
2014-04-28 12:02 ` [PATCH 00/21] MIPS: KVM: Fixes and guest timer rewrite Paolo Bonzini
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