linux-kernel - Re: [PATCH v4 2/5] arm64: errata: Assume that unknown CPUs _are

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Message-ID: <Z6zf3YJq6qqoJQRi@arm.com>
Date: Wed, 12 Feb 2025 17:52:29 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: Doug Anderson <dianders@...omium.org>
Cc: James Morse <james.morse@....com>, Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Roxana Bradescu <roxabee@...gle.com>,
	Julius Werner <jwerner@...omium.org>,
	bjorn.andersson@....qualcomm.com,
	Trilok Soni <quic_tsoni@...cinc.com>, linux-arm-msm@...r.kernel.org,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	linux-arm-kernel@...ts.infradead.org,
	Jeffrey Hugo <quic_jhugo@...cinc.com>,
	Scott Bauer <sbauer@...cinc.com>, stable@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/5] arm64: errata: Assume that unknown CPUs _are_
 vulnerable to Spectre BHB

On Wed, Jan 29, 2025 at 11:14:20AM -0800, Doug Anderson wrote:
> On Wed, Jan 29, 2025 at 8:43 AM James Morse <james.morse@....com> wrote:
> > Arm have recently updated that table of CPUs
> > with extra entries (thanks for picking those up!) - but now that patch can't be easily
> > applied to older kernels.
> > I suspect making the reporting assuming-vulnerable may make other CPUs come out of the
> > wood work too...
> >
> > Could we avoid changing this unless we really need to?
> 
> Will / Catalin: Do either of you have an opinion here?

Is this about whether to report "vulnerable" for unknown CPUs? I think
Will suggested this:

https://lore.kernel.org/all/20241219175128.GA25477@willie-the-truck/

That said, some patch splitting will help to make review easier. Should
such change be back-portable as well? I think so, it's not only for CPUs
we'll see in the future.

-- 
Catalin