From: Avi Kivity <avi@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, kvm <kvm@vger.kernel.org>,
qemu-devel <qemu-devel@nongnu.org>,
qemu-stable <qemu-stable@nongnu.org>
Subject: Re: [PATCH uq/master] kvm: i8254: Fix conversion of in-kernel to userspace state
Date: Mon, 11 Jun 2012 13:07:14 +0300 [thread overview]
Message-ID: <4FD5C352.4000004@redhat.com> (raw)
In-Reply-To: <4FCF691A.10502@siemens.com>
On 06/06/2012 05:28 PM, Jan Kiszka wrote:
> Due to a offset between the clock used to generate the in-kernel
> count_load_time (CLOCK_MONOTONIC) and the clock used for processing this
> in userspace (vm_clock), reading back the output of PIT channel 2 via
> port 0x61 was broken. One use cases that suffered from it was the CPU
> frequency calibration of SeaBIOS, which also affected IDE/AHCI timeouts.
>
> This fixes it by calibrating the offset between both clocks on
> kvm_pit_get and adjusting the kernel value before saving it in the
> userspace state. As the calibration only works while the vm_clock is
> running, we cache the in-kernel state across stopped phases.
Applied, thanks.
> + clock_offset = LLONG_MAX;
INT64_MAX would me more strictly correct, but in practice it makes no
difference.
--
error compiling committee.c: too many arguments to function
WARNING: multiple messages have this Message-ID (diff)
From: Avi Kivity <avi@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>, kvm <kvm@vger.kernel.org>,
qemu-stable <qemu-stable@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH uq/master] kvm: i8254: Fix conversion of in-kernel to userspace state
Date: Mon, 11 Jun 2012 13:07:14 +0300 [thread overview]
Message-ID: <4FD5C352.4000004@redhat.com> (raw)
In-Reply-To: <4FCF691A.10502@siemens.com>
On 06/06/2012 05:28 PM, Jan Kiszka wrote:
> Due to a offset between the clock used to generate the in-kernel
> count_load_time (CLOCK_MONOTONIC) and the clock used for processing this
> in userspace (vm_clock), reading back the output of PIT channel 2 via
> port 0x61 was broken. One use cases that suffered from it was the CPU
> frequency calibration of SeaBIOS, which also affected IDE/AHCI timeouts.
>
> This fixes it by calibrating the offset between both clocks on
> kvm_pit_get and adjusting the kernel value before saving it in the
> userspace state. As the calibration only works while the vm_clock is
> running, we cache the in-kernel state across stopped phases.
Applied, thanks.
> + clock_offset = LLONG_MAX;
INT64_MAX would me more strictly correct, but in practice it makes no
difference.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-06-11 10:07 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-06 14:28 [PATCH uq/master] kvm: i8254: Fix conversion of in-kernel to userspace state Jan Kiszka
2012-06-06 14:28 ` [Qemu-devel] " Jan Kiszka
2012-06-11 10:07 ` Avi Kivity [this message]
2012-06-11 10:07 ` Avi Kivity
2012-06-11 10:29 ` [PATCH] KVM: i8254: Clean up limit constant Jan Kiszka
2012-06-11 10:29 ` [Qemu-devel] " Jan Kiszka
2012-06-11 11:18 ` Avi Kivity
2012-06-11 11:18 ` [Qemu-devel] " Avi Kivity
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