linux-kernel - Re: [RFC PATCH v1 0/3] put arm64 kvm_config on a diet

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Message-ID: <87o8nqmpsj.fsf@linaro.org>
Date:   Tue, 04 Aug 2020 15:47:08 +0100
From:   Alex Bennée <alex.bennee@...aro.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     kvm@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Marc Zyngier <maz@...nel.org>,
        Christoffer Dall <christoffer.dall@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kvmarm <kvmarm@...ts.cs.columbia.edu>
Subject: Re: [RFC PATCH v1 0/3] put arm64 kvm_config on a diet

Ard Biesheuvel <ardb@...nel.org> writes:

> On Tue, 4 Aug 2020 at 14:45, Alex Bennée <alex.bennee@...aro.org> wrote:
>>
>> Hi,
>>
>> When building guest kernels for virtualisation we were bringing in a
>> bunch of stuff from physical hardware which we don't need for our
>> idealised fixable virtual PCI devices. This series makes some Kconfig
>> changes to allow the ThunderX and XGene PCI drivers to be compiled
>> out. It also drops PCI_QUIRKS from the KVM guest build as a virtual
>> PCI device should be quirk free.
>>
>
> What about PCI passthrough?

That is a good point - how much of the host PCI controller is visible to
a pass-through guest?

AIUI in passthrough the driver only interacts with the particular cards
IO window. How many quirks are visible just at the device level (rather
than the bus itself)?

That said I think the last patch might get dropped as long as the user
has the option to slim down their kernel with the first two.

>
>> This is my first time hacking around Kconfig so I hope I've got the
>> balance between depends and selects right but please let be know if it
>> could be specified in a cleaner way.
>>
>> Alex Bennée (3):
>>   arm64: allow de-selection of ThunderX PCI controllers
>>   arm64: gate the whole of pci-xgene on CONFIG_PCI_XGENE
>>   kernel/configs: don't include PCI_QUIRKS in KVM guest configs
>>
>>  arch/arm64/Kconfig.platforms    | 2 ++
>>  arch/arm64/configs/defconfig    | 1 +
>>  drivers/pci/controller/Kconfig  | 7 +++++++
>>  drivers/pci/controller/Makefile | 8 +++-----
>>  kernel/configs/kvm_guest.config | 1 +
>>  5 files changed, 14 insertions(+), 5 deletions(-)
>>
>> --
>> 2.20.1
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@...ts.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

-- 
Alex Bennée

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