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From: Paolo Bonzini <pbonzini@redhat.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Sean Christopherson <seanjc@google.com>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Guo Ren <guoren@kernel.org>, Nick Hu <nickhu@andestech.com>,
	Greentime Hu <green.hu@gmail.com>,
	Vincent Chen <deanbo422@gmail.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Juergen Gross <jgross@suse.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Stefano Stabellini <sstabellini@kernel.org>,
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-csky@vger.kernel.org,
	linux-riscv@lists.infradead.org, kvm@vger.kernel.org,
	xen-devel@lists.xenproject.org,
	Artem Kashkanov <artem.kashkanov@intel.com>,
	Like Xu <like.xu.linux@gmail.com>,
	Zhu Lingshan <lingshan.zhu@intel.com>
Subject: Re: [PATCH v2 00/13] perf: KVM: Fix, optimize, and clean up callbacks
Date: Mon, 20 Sep 2021 20:22:50 +0200	[thread overview]
Message-ID: <0eb2d4b1-23a4-c318-9f91-8dce78c6c8ad@redhat.com> (raw)
In-Reply-To: <87o88nuzzc.wl-maz@kernel.org>

On 20/09/21 15:40, Marc Zyngier wrote:
>>> At least not before we
>>> declare the arm64 single kernel image policy to be obsolete.
>>
>> --verbose please.:)   I am sure you're right, but I don't understand
>> the link between the two.
>
> To start making KVM/arm64 modular, you'd have to build it such as
> there is no support for the nVHE hypervisor anymore. Which would mean
> two different configs (one that can only work with VHE, and one for
> the rest) and contradicts the current single kernel image policy.

Ah okay, I interpreted the policy as "it's possible to build a single 
kernel image but it would be possible to build an image for a subset of 
the features as well".

In that case you could have one config that can work either with or 
without VHE (and supports y/n) and one config that can only work with 
VHE (and supports y/m/n).  The code to enter VHE EL2 would of course 
always be builtin.

> It is bad enough that we have to support 3 sets of page sizes.
> Doubling the validation space for the sake of being able to unload KVM
> seems a dubious prospect.

It's not even a configuration that matches kconfig very well, since it 
does have a way to build something *only as a module*, but not a way to 
build something only as built-in.

That said, if you had the possibility to unload/reload KVM, you'll 
quickly become unable to live without it. :)

Paolo


      reply	other threads:[~2021-09-20 18:29 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-28  0:35 Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 01/13] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref Sean Christopherson
2021-08-28 19:44   ` Peter Zijlstra
2021-09-16 21:41     ` Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 02/13] KVM: x86: Register perf callbacks after calling vendor's hardware_setup() Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 03/13] KVM: x86: Register Processor Trace interrupt hook iff PT enabled in guest Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 04/13] perf: Stop pretending that perf can handle multiple guest callbacks Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 05/13] perf: Force architectures to opt-in to " Sean Christopherson
2021-08-28 19:47   ` Peter Zijlstra
2021-09-16 22:30     ` Sean Christopherson
2021-09-21 16:44     ` Paolo Bonzini
2021-09-21 21:29       ` Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 06/13] perf/core: Rework guest callbacks to prepare for static_call support Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 07/13] perf/core: Use static_call to optimize perf_guest_info_callbacks Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 08/13] KVM: x86: Drop current_vcpu for kvm_running_vcpu + kvm_arch_vcpu variable Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 09/13] KVM: x86: More precisely identify NMI from guest when handling PMI Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 10/13] KVM: Move x86's perf guest info callbacks to generic KVM Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 11/13] KVM: x86: Move Intel Processor Trace interrupt handler to vmx.c Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 12/13] KVM: arm64: Convert to the generic perf callbacks Sean Christopherson
2021-08-28  0:35 ` [PATCH v2 13/13] KVM: arm64: Drop perf.c and fold its tiny bits of code into arm.c / pmu.c Sean Christopherson
2021-08-28 20:13 ` [PATCH v2 00/13] perf: KVM: Fix, optimize, and clean up callbacks Peter Zijlstra
2021-09-16 21:37   ` Sean Christopherson
2021-09-17  7:28     ` Peter Zijlstra
2021-09-17 16:53       ` Sean Christopherson
2021-09-20 12:05       ` Paolo Bonzini
2021-09-20 12:22         ` Marc Zyngier
2021-09-20 13:18           ` Paolo Bonzini
2021-09-20 13:40             ` Marc Zyngier
2021-09-20 18:22               ` Paolo Bonzini [this message]

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