From: dave.martin@linaro.org (Dave Martin)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCHv5 15/16] ARM: hyp: initialize CNTVOFF to zero
Date: Fri, 1 Feb 2013 11:13:50 +0000 [thread overview]
Message-ID: <20130201111350.GA1970@linaro.org> (raw)
In-Reply-To: <1359634539-9580-16-git-send-email-mark.rutland@arm.com>
On Thu, Jan 31, 2013 at 12:15:38PM +0000, Mark Rutland wrote:
> From: Marc Zyngier <Marc.Zyngier@arm.com>
>
> In order to be able to use the virtual counter in a safe way,
> make sure it is initialized to zero before dropping to SVC.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Dave Martin <dave.martin@arm.com>
> ---
> arch/arm/kernel/hyp-stub.S | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S
> index 65b2417..455603a 100644
> --- a/arch/arm/kernel/hyp-stub.S
> +++ b/arch/arm/kernel/hyp-stub.S
> @@ -152,6 +152,9 @@ THUMB( orr r7, #(1 << 30) ) @ HSCTLR.TE
> mrc p15, 4, r7, c14, c1, 0 @ CNTHCTL
> orr r7, r7, #3 @ PL1PCEN | PL1PCTEN
> mcr p15, 4, r7, c14, c1, 0 @ CNTHCTL
> + mov r6, #0
> + mov r7, #0
> + mcrr p15, 4, r6, r7, c14 @ CNTVOFF
Is this required for safety, or is it more a sanity feature?
The architected timer counters are supposed to be monotonic time sources
only, so applying a random offset shouldn't really change anything.
The main thing I can think of is that it is easier for the host to
manage guests' virtual counter offsets if the host's offset is 0 (and
we don't really want to be changing the host offset after the host kernel
boots).
Cheers
---Dave
next prev parent reply other threads:[~2013-02-01 11:13 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-31 12:15 [PATCHv5 00/16] Unify arm_generic and arch_timer drivers Mark Rutland
2013-01-31 12:15 ` [PATCHv5 01/16] arm: arch_timer: balance device_node refcounting Mark Rutland
2013-01-31 15:33 ` Catalin Marinas
2013-01-31 12:15 ` [PATCHv5 02/16] arm: arch_timer: remove redundant available check Mark Rutland
2013-01-31 12:15 ` [PATCHv5 03/16] arm: arch_timer: use u64/u32 for register data Mark Rutland
2013-01-31 12:15 ` [PATCHv5 04/16] arm: arch_timer: standardise counter reading Mark Rutland
2013-01-31 15:34 ` Catalin Marinas
2013-01-31 12:15 ` [PATCHv5 05/16] arm: arch_timer: split cntfrq accessor Mark Rutland
2013-01-31 12:15 ` [PATCHv5 06/16] arm: arch_timer: factor out register accessors Mark Rutland
2013-01-31 12:15 ` [PATCHv5 07/16] arm: arch_timer: add isbs to " Mark Rutland
2013-01-31 15:35 ` Catalin Marinas
2013-01-31 12:15 ` [PATCHv5 08/16] arm: arch_timer: divorce from local_timer api Mark Rutland
2013-01-31 12:15 ` [PATCHv5 09/16] arm: arch_timer: add arch_counter_set_user_access Mark Rutland
2013-01-31 15:36 ` Catalin Marinas
2013-01-31 12:15 ` [PATCHv5 10/16] arm: arch_timer: move core to drivers/clocksource Mark Rutland
2013-01-31 12:15 ` [PATCHv5 11/16] arm64: arm_generic: prevent reading stale time Mark Rutland
2013-01-31 15:36 ` Catalin Marinas
2013-01-31 12:15 ` [PATCHv5 12/16] arm64: move from arm_generic to arm_arch_timer Mark Rutland
2013-01-31 12:15 ` [PATCHv5 13/16] Documentation: Add ARMv8 to arch_timer devicetree Mark Rutland
2013-01-31 12:15 ` [PATCHv5 14/16] ARM: arch_timers: switch to physical timers if HYP mode is available Mark Rutland
2013-01-31 15:37 ` Catalin Marinas
2013-01-31 12:15 ` [PATCHv5 15/16] ARM: hyp: initialize CNTVOFF to zero Mark Rutland
2013-02-01 11:13 ` Dave Martin [this message]
2013-02-01 11:43 ` Marc Zyngier
2013-02-01 11:46 ` Mark Rutland
2013-02-01 18:07 ` Dave Martin
2013-02-04 9:29 ` Mark Rutland
2013-01-31 12:15 ` [PATCHv5 16/16] clocksource: arch_timer: use virtual counters Mark Rutland
2013-01-31 15:38 ` Catalin Marinas
2013-01-31 17:39 ` [PATCHv5 00/16] Unify arm_generic and arch_timer drivers Stephen Warren
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130201111350.GA1970@linaro.org \
--to=dave.martin@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).