From: marc.zyngier@arm•com (Marc Zyngier)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 0/9] arm64: KVM: debug infrastructure support
Date: Mon, 19 May 2014 13:22:13 +0100 [thread overview]
Message-ID: <87tx8m3qmi.fsf@approximate.cambridge.arm.com> (raw)
In-Reply-To: <CALrVBktviU6qs_N3AoRd0=BKEVRar65FBca8uQLkzZiuetNkVg@mail.gmail.com> (Anup Patel's message of "Mon, 19 May 2014 10:35:58 +0100")
On Mon, May 19 2014 at 10:35:58 am BST, Anup Patel <anup.patel@linaro•org> wrote:
> On 19 May 2014 14:58, Marc Zyngier <marc.zyngier@arm•com> wrote:
>> On Mon, May 19 2014 at 10:05:42 am BST, Anup Patel
>> <anup.patel@linaro•org> wrote
>>
>> Hi Anup,
>>
>>> Overall the patchset looks good to me.
>>>
>>> The debug register usage by Guest will be very rare
>>> so a lazy save/restore makes lot-of-sense here.
>>>
>>> The only concern here is that amount of time spend in
>>> world-switch will increase for Guest once Guest starts
>>> accessing debug registers.
>>>
>>> I was wondering if it is possible to detect that Guest
>>> has stopped using debug HW and we can mark debug
>>> state as clean. (or something similar)
>>
>> If you look carefully at patch #8 (last hunk of the patch), you'll see
>> that I always reset the debug state to "clean" at the end of a guest
>> run:
>>
>> @@ -609,6 +1040,12 @@ __kvm_vcpu_return:
>>
>> bl __restore_sysregs
>> bl __restore_fpsimd
>> +
>> + skip_clean_debug_state x3, 1f
>> + // Clear the dirty flag for the next run
>> + str xzr, [x0, #VCPU_DEBUG_FLAGS]
>> + bl __restore_debug
>> +1:
>> restore_host_regs
>>
>> mov x0, x1
>>
>> This ensures that the guest's debug state will only be reloaded if:
>>
>> - MDSCR_EL1 has either MDE or KDE set (which means the guest is actively
>> using the debug infrastructure)
>> - or the guest has written to a trapped register (which marks the state
>> as dirty).
>
> Thanks for pointing out.
>
> Can you add this info as comment in patch#8 where you
> clear the dirty flag?
Right. There is already some comments to that effect just above, where
we compute the dirty state, but I think it doesn't hurt to repeat it.
Thanks,
M.
--
Jazz is not dead. It just smells funny.
next prev parent reply other threads:[~2014-05-19 12:22 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-07 15:20 [PATCH 0/9] arm64: KVM: debug infrastructure support Marc Zyngier
2014-05-07 15:20 ` [PATCH 1/9] arm64: KVM: rename pm_fake handler to trap_wi_raz Marc Zyngier
2014-05-07 15:34 ` Peter Maydell
2014-05-07 15:42 ` Marc Zyngier
2014-05-19 8:43 ` Anup Patel
2014-05-07 15:20 ` [PATCH 2/9] arm64: move DBG_MDSCR_* to asm/debug-monitors.h Marc Zyngier
2014-05-07 17:14 ` Will Deacon
2014-05-07 15:20 ` [PATCH 3/9] arm64: KVM: add trap handlers for AArch64 debug registers Marc Zyngier
2014-05-19 8:27 ` Anup Patel
2014-05-07 15:20 ` [PATCH 4/9] arm64: KVM: common infrastructure for handling AArch32 CP14/CP15 Marc Zyngier
2014-05-19 8:29 ` Anup Patel
2014-05-07 15:20 ` [PATCH 5/9] arm64: KVM: use separate tables for AArch32 32 and 64bit traps Marc Zyngier
2014-05-19 8:29 ` Anup Patel
2014-05-07 15:20 ` [PATCH 6/9] arm64: KVM: check ordering of all system register tables Marc Zyngier
2014-05-19 8:31 ` Anup Patel
2014-05-07 15:20 ` [PATCH 7/9] arm64: KVM: add trap handlers for AArch32 debug registers Marc Zyngier
2014-05-19 8:33 ` Anup Patel
2014-05-07 15:20 ` [PATCH 8/9] arm64: KVM: implement lazy world switch for " Marc Zyngier
2014-05-19 8:38 ` Anup Patel
2014-05-19 16:01 ` Marc Zyngier
2014-05-07 15:20 ` [PATCH 9/9] arm64: KVM: enable trapping of all " Marc Zyngier
2014-05-19 8:40 ` Anup Patel
2014-05-07 15:42 ` [PATCH 0/9] arm64: KVM: debug infrastructure support Peter Maydell
2014-05-07 15:57 ` Marc Zyngier
2014-05-19 9:05 ` Anup Patel
2014-05-19 9:28 ` Marc Zyngier
2014-05-19 9:35 ` Anup Patel
2014-05-19 12:22 ` Marc Zyngier [this message]
2014-05-19 12:32 ` Peter Maydell
2014-05-19 12:59 ` Marc Zyngier
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