From: Marc Zyngier <maz@kernel.org>
To: minyard@acm.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Corey Minyard <cminyard@mvista.com>
Subject: Re: [PATCH v2] arm64:kgdb: Fix kernel single-stepping
Date: Thu, 20 Feb 2020 14:21:36 +0000 [thread overview]
Message-ID: <1416dca51b52dff349923184f41d48e8@kernel.org> (raw)
In-Reply-To: <20200219152403.3495-1-minyard@acm.org>
On 2020-02-19 15:24, minyard@acm.org wrote:
> From: Corey Minyard <cminyard@mvista.com>
[...]
> After studying the EL0 handling for this, I realized an issue with
> using
> MDSCR to check if single step is enabled: it can be expensive on a VM.
> So check the task flag first to see if single step is enabled. Then
> check MDSCR if the task flag is set.
Very tangential remark: I'd really like people *not* to try and optimize
Linux based on the behaviour of a hypervisor. In general, reading a
system register is fast, and the fact that it traps on a given
hypervisor
at some point may not be true in the future, nor be a valid assumption
across hypervisors.
M.
--
Jazz is not dead. It just smells funny...
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: minyard@acm.org
Cc: Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org,
Corey Minyard <cminyard@mvista.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] arm64:kgdb: Fix kernel single-stepping
Date: Thu, 20 Feb 2020 14:21:36 +0000 [thread overview]
Message-ID: <1416dca51b52dff349923184f41d48e8@kernel.org> (raw)
In-Reply-To: <20200219152403.3495-1-minyard@acm.org>
On 2020-02-19 15:24, minyard@acm.org wrote:
> From: Corey Minyard <cminyard@mvista.com>
[...]
> After studying the EL0 handling for this, I realized an issue with
> using
> MDSCR to check if single step is enabled: it can be expensive on a VM.
> So check the task flag first to see if single step is enabled. Then
> check MDSCR if the task flag is set.
Very tangential remark: I'd really like people *not* to try and optimize
Linux based on the behaviour of a hypervisor. In general, reading a
system register is fast, and the fact that it traps on a given
hypervisor
at some point may not be true in the future, nor be a valid assumption
across hypervisors.
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2020-02-20 14:21 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 15:24 [PATCH v2] arm64:kgdb: Fix kernel single-stepping minyard
2020-02-19 15:24 ` minyard
2020-02-20 14:06 ` Daniel Thompson
2020-02-20 14:06 ` Daniel Thompson
2020-02-20 14:52 ` Corey Minyard
2020-02-20 14:52 ` Corey Minyard
2020-02-20 14:21 ` Marc Zyngier [this message]
2020-02-20 14:21 ` Marc Zyngier
2020-02-20 14:50 ` Corey Minyard
2020-02-20 14:50 ` Corey Minyard
2020-02-20 15:06 ` Marc Zyngier
2020-02-20 15:06 ` Marc Zyngier
2020-02-20 14:22 ` Will Deacon
2020-02-20 14:22 ` Will Deacon
2020-02-20 16:30 ` Corey Minyard
2020-02-20 16:30 ` Corey Minyard
2020-02-20 21:30 ` Corey Minyard
2020-02-20 21:30 ` Corey Minyard
2020-02-24 18:07 ` James Morse
2020-02-24 18:07 ` James Morse
2020-02-25 15:38 ` Corey Minyard
2020-02-25 15:38 ` Corey Minyard
2020-02-25 17:55 ` James Morse
2020-02-25 17:55 ` James Morse
2020-02-26 2:58 ` Corey Minyard
2020-02-26 2:58 ` Corey Minyard
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