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From: Zenghui Yu <yuzenghui@huawei.com>
To: James Morse <james.morse@arm.com>
Cc: <linux-arm-kernel@lists.infradead.org>,
	<kvmarm@lists.cs.columbia.edu>, <kvm@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>,
	<linux-perf-users@vger.kernel.org>, <marc.zyngier@arm.com>,
	<catalin.marinas@arm.com>, <will.deacon@arm.com>,
	<acme@kernel.org>, <linuxarm@huawei.com>, <acme@redhat.com>,
	<peterz@infradead.org>, <alexander.shishkin@linux.intel.com>,
	<mingo@redhat.com>, <ganapatrao.kulkarni@cavium.com>,
	<namhyung@kernel.org>, <jolsa@redhat.com>,
	<xiexiangyou@huawei.com>,
	"Wanghaibin (D)" <wanghaibin.wang@huawei.com>
Subject: Re: [PATCH v1 1/5] KVM: arm/arm64: Remove kvm_mmio_emulate tracepoint
Date: Thu, 13 Jun 2019 19:20:19 +0800
Message-ID: <5885c607-1314-ff53-38f1-9f48b1c16de4@huawei.com> (raw)
In-Reply-To: <e915c19a-51df-be88-ea3a-7c9a211f4518@arm.com>

Hi James,

On 2019/6/12 20:48, James Morse wrote:
> Hi,
> 
> On 12/06/2019 10:08, Zenghui Yu wrote:
>> In current KVM/ARM code, no one will invoke trace_kvm_mmio_emulate().
>> Remove this TRACE_EVENT definition.
> 
> Oooer. We can't just go removing these things, they are visible to user-space.
> 
> I recall an article on this: https://lwn.net/Articles/737530/
> "Another attempt to address the tracepoint ABI problem"
> 
> I agree this is orphaned, it was added by commit 45e96ea6b369 ("KVM: ARM: Handle I/O
> aborts"), but there never was a caller.
> 
> The problem with removing it is /sys/kernel/debug/tracing/events/kvm/kvm_mmio_emulate
> disappears. Any program relying on that being present (but useless) is now broken.
Thanks for the reminder.

It turned out that I knew little about the tracepoint ABI :( .
I'm OK to just drop this patch in next version.


Thanks,
zenghui


.



  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-12  9:08 [PATCH v1 0/5] perf kvm: Add stat support on arm64 Zenghui Yu
2019-06-12  9:08 ` [PATCH v1 1/5] KVM: arm/arm64: Remove kvm_mmio_emulate tracepoint Zenghui Yu
2019-06-12 12:48   ` James Morse
2019-06-13 11:20     ` Zenghui Yu [this message]
2019-06-12  9:08 ` [PATCH v1 2/5] KVM: arm/arm64: Adjust entry/exit and trap related tracepoints Zenghui Yu
2019-06-12 12:49   ` James Morse
2019-06-13 11:28     ` Zenghui Yu
2019-06-17 11:19       ` James Morse
2019-06-21 13:25         ` Zenghui Yu
2019-06-12  9:08 ` [PATCH v1 3/5] perf tools arm64: Add support for get_cpuid() function Zenghui Yu
2019-06-12  9:08 ` [PATCH v1 4/5] perf,kvm/arm64: Add stat support on arm64 Zenghui Yu
2019-06-12  9:08 ` [PATCH v1 5/5] perf,kvm/arm64: perf-kvm-stat to report VM TRAP Zenghui Yu

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