Messages in this thread | | | Subject | Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility | From | Srinivas Ramana <> | Date | Mon, 11 Jan 2021 12:38:43 -0800 |
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Hi Catalin,
On 1/11/2021 10:41 AM, Catalin Marinas wrote: > Hi Marc, > > On Mon, Jan 11, 2021 at 01:27:59PM +0000, Marc Zyngier wrote: >> Add a facility to globally override a feature, no matter what >> the HW says. Yes, this is dangerous. > Yeah, it's dangerous. We can make it less so if we only allow safe > values (e.g. lower if FTR_UNSIGNED). > >> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h >> index 9a555809b89c..465d2cb63bfc 100644 >> --- a/arch/arm64/include/asm/cpufeature.h >> +++ b/arch/arm64/include/asm/cpufeature.h >> @@ -75,6 +75,8 @@ struct arm64_ftr_reg { >> u64 sys_val; >> u64 user_val; >> const struct arm64_ftr_bits *ftr_bits; >> + u64 *override_val; >> + u64 *override_mask; >> }; > At the arm64_ftr_reg level, we don't have any information about the safe > values for a feature. Could we instead move this to arm64_ftr_bits? We > probably only need a single field. When populating the feature values, > we can make sure it doesn't go above the hardware one. > > I attempted a feature modification for MTE here, though I dropped the > entire series in the meantime as we clarified the ARM ARM: > > https://lore.kernel.org/linux-arm-kernel/20200515171612.1020-24-catalin.marinas@arm.com/ > > Srinivas copied it in his patch (but forgot to give credit ;)):
Sorry about that. I did mention that its taken from your patch-set in my cover letter. But missed your signed-off-by in the patch.
https://lore.kernel.org/linux-arm-msm/6dfdf691b5ed57df81c4c61422949af5@misterjones.org/T/#m1ae76e6096c07ab5f1636a4e383a3fd6cfb4665f
Since we can ignore my patch with the mechanism added by Marc, I am not re-sending this. Thanks.
> > https://lore.kernel.org/linux-arm-msm/1610152163-16554-3-git-send-email-sramana@codeaurora.org/ > > The above adds a filter function but, instead, just use your mechanism in > this series for idreg.feature setting via cmdline. The arm64_ftr_value() > function extracts the hardware value and lowers it if a cmdline argument > was passed. >
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