From: Peter Collingbourne <pcc@google.com>
To: Evgenii Stepanov <eugenis@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Kenny Root <kroot@google.com>, Marc Zyngier <maz@kernel.org>,
Will Deacon <will@kernel.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Mark Brown <broonie@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel test robot <lkp@intel.com>
Subject: Re: [PATCH v4] arm64: mte: move register initialization to C
Date: Fri, 9 Sep 2022 17:54:13 -0700 [thread overview]
Message-ID: <CAMn1gO4X93khAqOOvCJjWmm410rv8S5847GfsPckJwqtLSzc-Q@mail.gmail.com> (raw)
In-Reply-To: <20220907003630.1115439-1-eugenis@google.com>
On Tue, Sep 6, 2022 at 5:36 PM Evgenii Stepanov <eugenis@google.com> wrote:
>
> If FEAT_MTE2 is disabled via the arm64.nomte command line argument on a
> CPU that claims to support FEAT_MTE2, the kernel will use Tagged Normal
> in the MAIR. If we interpret arm64.nomte to mean that the CPU does not
> in fact implement FEAT_MTE2, setting the system register like this may
> lead to UNSPECIFIED behavior. Fix it by arranging for MAIR to be set
> in the C function cpu_enable_mte which is called based on the sanitized
> version of the system register.
>
> There is no need for the rest of the MTE-related system register
> initialization to happen from assembly, with the exception of TCR_EL1,
> which must be set to include at least TBI1 because the secondary CPUs
> access KASan-allocated data structures early. Therefore, make the TCR_EL1
> initialization unconditional and move the rest of the initialization to
> cpu_enable_mte so that we no longer have a dependency on the unsanitized
> ID register value.
Moving the register initialization to C also fixes a bug where the
kernel's zeroing of TFSR_EL1 has no practical effect when the kernel
is started in VHE mode because the register is currently being zeroed
prior to the kernel enabling the redirect of TFSR_EL2 to TFSR_EL1 when
it enables VHE. As a result, without this patch it is possible to get
a spurious KASAN error report if TFSR_EL2 is non-zero out of reset.
Peter
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next prev parent reply other threads:[~2022-09-10 0:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-07 0:36 [PATCH v4] arm64: mte: move register initialization to C Evgenii Stepanov
2022-09-10 0:54 ` Peter Collingbourne [this message]
2022-09-12 20:04 ` Catalin Marinas
2022-09-13 20:32 ` Peter Collingbourne
2022-09-14 12:09 ` Catalin Marinas
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