linux-kernel - Re: [PATCH v7 10/11] virt: arm-cca-guest: TSM

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Message-ID: <Z1GTu1kAV3J1cnJc@arm.com>
Date: Thu, 5 Dec 2024 11:51:23 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Steven Price <steven.price@....com>, kvm@...r.kernel.org,
	kvmarm@...ts.linux.dev, Sami Mujawar <sami.mujawar@....com>,
	Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
	James Morse <james.morse@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Joey Gouly <joey.gouly@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	Christoffer Dall <christoffer.dall@....com>,
	Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
	Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
	Gavin Shan <gshan@...hat.com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	Alper Gun <alpergun@...gle.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@...nel.org>
Subject: Re: [PATCH v7 10/11] virt: arm-cca-guest: TSM_REPORT support for
 realms

On Wed, Dec 04, 2024 at 01:16:05PM -0800, Dan Williams wrote:
> Steven Price wrote:
> > diff --git a/drivers/virt/coco/arm-cca-guest/Kconfig b/drivers/virt/coco/arm-cca-guest/Kconfig
> > new file mode 100644
> > index 000000000000..9dd27c3ee215
> > --- /dev/null
> > +++ b/drivers/virt/coco/arm-cca-guest/Kconfig
> > @@ -0,0 +1,11 @@
> > +config ARM_CCA_GUEST
> > +	tristate "Arm CCA Guest driver"
> > +	depends on ARM64
> > +	default m
> 
> I am working on some updates to the TSM_REPORTS interface, rebased them
> to test the changes with this driver, and discovered that this driver is
> enabled by default.
> 
> Just a reminder to please do not mark new drivers as "default m" [1]. In
> this case it is difficult to imagine that every arm64 kernel on the
> planet needs this functionality enabled by default. In general, someone
> should be able to run olddefconfig with a new kernel and not be exposed
> to brand new drivers that they have not considered previously.
> 
> [1]: http://lore.kernel.org/CA+55aFzxL6-Xp=-mnBwMisZsuKhRZ6zRDJoAmH8W5LDHU2oJuw@mail.gmail.com/

Fair point, the pKVM driver is also default off. At least with the arm64
defconfig, VIRT_DRIVERS is default off, so this wouldn't be built. But
an olddefconfig will indeed enable it (this reminds me to add the coco
drivers to my test configs).

-- 
Catalin