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From: Richard Weinberger <richard@nod.at>
To: "Haibo Xu (Arm Technology China)" <Haibo.Xu@arm.com>
Cc: Will Deacon <Will.Deacon@arm.com>,
	Catalin Marinas <Catalin.Marinas@arm.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	nd <nd@arm.com>, "jdike@addtoit.com" <jdike@addtoit.com>
Subject: Re: 答复: [PATCH] arm64/ptrace: add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support
Date: Tue, 04 Sep 2018 21:45:06 +0200	[thread overview]
Message-ID: <3641125.aEYyuDiOni@blindfold> (raw)
In-Reply-To: <AM4PR08MB29297B27FCC0E8696473523185030@AM4PR08MB2929.eurprd08.prod.outlook.com>

Am Dienstag, 4. September 2018, 04:11:07 CEST schrieb Haibo Xu (Arm Technology China):
> Hi Richard,
> 
> What do you mean by done it in the core? moving macro definition to include/uapi/linux/ptrace.h?
> The patch is strictly follow x86's sematic on PTRACE_SYSEMU/SINGLESTEP support.

Well, the feature itself is not really architecture specific.
Just because x86 does it in arch/x86, it does not mean that this is the best way.
I guess this is also what Will tried to say.
If we can, we should implement PTRACE_SYSEMU in the core ptrace code and not
per architecture.

> > > I wonder what Haibo Xu want to do with PTRACE_SYSEMU on arm64.
> > > Are you porting UML or gvisor to arm64?
> >
> > That's a good question. Haibo?
> 
> The story is we are working on a container runtime(Google Gvisor) support on ARM64 platform,
> and the Gvisor depend on Linux kernel PTRACE_SYSEMU/SINGLESTEP support.

Gvisor also supports a kvm backend which should be *much* faster than PTRACE_SYSEMU.
Otherwise gvisor suffers from the same performance drawbacks as UML does.
Pagefaults via SIGSEGV/mmap, syscall gate via ptrace().

Did you check, is PTRACE_SYSEMU really the way to go for gvisor?
Last time I checked the KVM backend looked promising but still WIP, though.

I also wonder whether PTRACE_SYSEMU is really the only missing bit to support
gvisor on arm64. Did you check how to work around VIPT/VIVT caching issues?
UML (and gvisor in this context) have lots of implicit x86 dependencies.

Thanks,
//richard



WARNING: multiple messages have this Message-ID (diff)
From: richard@nod.at (Richard Weinberger)
To: linux-arm-kernel@lists.infradead.org
Subject: 答复: [PATCH] arm64/ptrace: add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support
Date: Tue, 04 Sep 2018 21:45:06 +0200	[thread overview]
Message-ID: <3641125.aEYyuDiOni@blindfold> (raw)
In-Reply-To: <AM4PR08MB29297B27FCC0E8696473523185030@AM4PR08MB2929.eurprd08.prod.outlook.com>

Am Dienstag, 4. September 2018, 04:11:07 CEST schrieb Haibo Xu (Arm Technology China):
> Hi Richard,
> 
> What do you mean by done it in the core? moving macro definition to include/uapi/linux/ptrace.h?
> The patch is strictly follow x86's sematic on PTRACE_SYSEMU/SINGLESTEP support.

Well, the feature itself is not really architecture specific.
Just because x86 does it in arch/x86, it does not mean that this is the best way.
I guess this is also what Will tried to say.
If we can, we should implement PTRACE_SYSEMU in the core ptrace code and not
per architecture.

> > > I wonder what Haibo Xu want to do with PTRACE_SYSEMU on arm64.
> > > Are you porting UML or gvisor to arm64?
> >
> > That's a good question. Haibo?
> 
> The story is we are working on a container runtime(Google Gvisor) support on ARM64 platform,
> and the Gvisor depend on Linux kernel PTRACE_SYSEMU/SINGLESTEP support.

Gvisor also supports a kvm backend which should be *much* faster than PTRACE_SYSEMU.
Otherwise gvisor suffers from the same performance drawbacks as UML does.
Pagefaults via SIGSEGV/mmap, syscall gate via ptrace().

Did you check, is PTRACE_SYSEMU really the way to go for gvisor?
Last time I checked the KVM backend looked promising but still WIP, though.

I also wonder whether PTRACE_SYSEMU is really the only missing bit to support
gvisor on arm64. Did you check how to work around VIPT/VIVT caching issues?
UML (and gvisor in this context) have lots of implicit x86 dependencies.

Thanks,
//richard

  reply	other threads:[~2018-09-04 19:45 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-03  6:23 [PATCH] arm64/ptrace: add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support Haibo.Xu
2018-09-03 16:31 ` Will Deacon
2018-09-03 16:31   ` Will Deacon
2018-09-03 16:40   ` Richard Weinberger
2018-09-03 16:40     ` Richard Weinberger
2018-09-03 16:57     ` Will Deacon
2018-09-03 16:57       ` Will Deacon
2018-09-04  2:11       ` 答复: " Haibo Xu (Arm Technology China)
2018-09-04  2:11         ` Haibo Xu (Arm Technology China)
2018-09-04 19:45         ` Richard Weinberger [this message]
2018-09-04 19:45           ` Richard Weinberger
2018-09-05 10:21           ` 答复: " Haibo Xu (Arm Technology China)
2018-09-05 10:21             ` Haibo Xu (Arm Technology China)
2018-10-16  2:54           ` Haibo Xu (Arm Technology China)
2018-10-16  2:54             ` Haibo Xu (Arm Technology China)

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