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Date: Mon, 2 Dec 2024 17:53:05 +0000
From: Mark Rutland <mark.rutland@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Vitaly Chikunov <vt@altlinux.org>, Will Deacon <will@kernel.org>,
	james.morse@arm.com, linux-arm-kernel@lists.infradead.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-kernel@vger.kernel.org, oliver.upton@linux.dev
Subject: Re: v6.13-rc1: Internal error: Oops - Undefined instruction:
 0000000002000000 [#1] SMP
Message-ID: <Z030AVd1_uURWsgL@J2N7QTR9R3>
References: <20241202045830.e4yy3nkvxtzaybxk@altlinux.org>
 <20241202153618.GA6834@willie-the-truck>
 <86ttbmt71k.wl-maz@kernel.org>
 <20241202155940.p267a3tz5ypj4sog@altlinux.org>
 <86ser6t6fs.wl-maz@kernel.org>
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In-Reply-To: <86ser6t6fs.wl-maz@kernel.org>

On Mon, Dec 02, 2024 at 04:07:03PM +0000, Marc Zyngier wrote:
> On Mon, 02 Dec 2024 15:59:40 +0000,
> Vitaly Chikunov <vt@altlinux.org> wrote:
> > 
> > Marc,
> > 
> > On Mon, Dec 02, 2024 at 03:53:59PM +0000, Marc Zyngier wrote:
> > >
> > > What the log doesn't say is what the host is. Is it 6.13-rc1 as well?
> > 
> > No, host is 6.6.60.
> 
> Right. I wouldn't be surprised if:
> 
> - this v6.6 kernel doesn't hide the MPAM feature as it should (and
>   that's proably something we should backport)

Looks like v6.6.60 is missing:

  6685f5d572c22e10 ("KVM: arm64: Disable MPAM visibility by default and ignore VMM writes")

... which is a fix for:

  011e5f5bf529f8ec (" arm64/cpufeature: Add remaining feature bits in ID_AA64PFR0 register")

... which unintentionally exposed ID_AA64PFR0.MPAM to guests, and *is*
in v6.6.60.

Mark.

> - you get a nastygram in the host log telling you that the guest has
>   executed something it shouldn't (you'll get the encoding of the
>   instruction)
> 
> Can you confirm these two things?
> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.