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From: Marc Zyngier <maz@kernel.org>
To: Will Deacon <will@kernel.org>
Cc: Srinivas Ramana <sramana@codeaurora.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Hector Martin <marcan@marcan.st>,
	linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	Ajay Patil <pajay@qti.qualcomm.com>,
	Prasad Sodagudi <psodagud@codeaurora.org>,
	kernel-team@android.com, Ard Biesheuvel <ardb@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v7 00/23] arm64: Early CPU feature override, and applications to VHE, BTI and PAuth
Date: Mon, 08 Feb 2021 15:02:22 +0000	[thread overview]
Message-ID: <240a0245f75d8368a4d90a5e6740dc7d@kernel.org> (raw)
In-Reply-To: <20210208143248.GA25934@willie-the-truck>

Hi Will,

On 2021-02-08 14:32, Will Deacon wrote:
> Hi Marc,
> 
> On Mon, Feb 08, 2021 at 09:57:09AM +0000, Marc Zyngier wrote:
>> It recently came to light that there is a need to be able to override
>> some CPU features very early on, before the kernel is fully up and
>> running. The reasons for this range from specific feature support
>> (such as using Protected KVM on VHE HW, which is the main motivation
>> for this work) to errata workaround (a feature is broken on a CPU and
>> needs to be turned off, or rather not enabled).
>> 
>> This series tries to offer a limited framework for this kind of
>> problems, by allowing a set of options to be passed on the
>> command-line and altering the feature set that the cpufeature
>> subsystem exposes to the rest of the kernel. Note that this doesn't
>> change anything for code that directly uses the CPU ID registers.
> 
> I applied this locally, but I'm seeing consistent boot failure under 
> QEMU when
> KASAN is enabled. I tried sprinkling some __no_sanitize_address 
> annotations
> around (see below) but it didn't help. The culprit appears to be
> early_fdt_map(), but looking a bit more closely, I'm really nervous 
> about the
> way we call into C functions from __primary_switched. Remember -- this 
> code
> runs _twice_ when KASLR is active: before and after the randomization. 
> This
> also means that any memory writes the first time around can be lost due 
> to
> the D-cache invalidation when (re-)creating the kernel page-tables.

Well, we already call into C functions with KASLR, and nothing explodes
with that, so I must be doing something else wrong.

I do have cache maintenance for the writes to the shadow registers, so 
that
part should be fine. But I think I'm missing some cache maintenance 
around
the FDT base itself, and I wonder what happens when we go around the 
loop.

I'll chase this down now.

Thanks for the heads up.

         M.
-- 
Jazz is not dead. It just smells funny...

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  parent reply	other threads:[~2021-02-08 15:03 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-08  9:57 [PATCH v7 00/23] arm64: Early CPU feature override, and applications to VHE, BTI and PAuth Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 01/23] arm64: Fix labels in el2_setup macros Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 02/23] arm64: Fix outdated TCR setup comment Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 03/23] arm64: Turn the MMU-on sequence into a macro Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 04/23] arm64: Provide an 'upgrade to VHE' stub hypercall Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 05/23] arm64: Initialise as nVHE before switching to VHE Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 06/23] arm64: Drop early setting of MDSCR_EL2.TPMS Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 07/23] arm64: Move VHE-specific SPE setup to mutate_to_vhe() Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 08/23] arm64: Simplify init_el2_state to be non-VHE only Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 09/23] arm64: Move SCTLR_EL1 initialisation to EL-agnostic code Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 10/23] arm64: cpufeature: Add global feature override facility Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 11/23] arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding() Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 12/23] arm64: Extract early FDT mapping from kaslr_early_init() Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 13/23] arm64: cpufeature: Add an early command-line cpufeature override facility Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 14/23] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 15/23] arm64: Honor VHE being disabled from the command-line Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 16/23] arm64: Add an aliasing facility for the idreg override Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 17/23] arm64: Make kvm-arm.mode={nvhe, protected} an alias of id_aa64mmfr1.vh=0 Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 18/23] KVM: arm64: Document HVC_VHE_RESTART stub hypercall Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 19/23] arm64: Move "nokaslr" over to the early cpufeature infrastructure Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 20/23] arm64: cpufeatures: Allow disabling of BTI from the command-line Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 21/23] arm64: Defer enabling pointer authentication on boot core Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 22/23] arm64: cpufeatures: Allow disabling of Pointer Auth from the command-line Marc Zyngier
2021-02-08  9:57 ` [PATCH v7 23/23] [DO NOT MERGE] arm64: Cope with CPUs stuck in VHE mode Marc Zyngier
2021-02-22  9:35   ` Jonathan Neuschäfer
2021-02-22  9:47     ` Marc Zyngier
2021-02-08 14:32 ` [PATCH v7 00/23] arm64: Early CPU feature override, and applications to VHE, BTI and PAuth Will Deacon
2021-02-08 14:40   ` Ard Biesheuvel
2021-02-08 15:02   ` Marc Zyngier [this message]
2021-02-08 16:30   ` Marc Zyngier

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