linux-kernel - Re: [PATCH] arm64: Add KRYO{3,4}XX CPU cores to spectre-v2 safe list

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Date:   Fri, 17 Jan 2020 01:34:43 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Doug Anderson <dianders@...omium.org>,
        Will Deacon <will@...nel.org>
Cc:     Jeffrey Hugo <jhugo@...eaurora.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Andre Przywara <andre.przywara@....com>,
        Mark Rutland <mark.rutland@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        James Morse <james.morse@....com>,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH] arm64: Add KRYO{3,4}XX CPU cores to spectre-v2 safe list

Hi,

On 2020-01-16 23:57, Doug Anderson wrote:
> Hi,
> 
> On Thu, Jan 16, 2020 at 8:11 AM Sai Prakash Ranjan
> <saiprakash.ranjan@...eaurora.org> wrote:
>> 
>> Hi Will,
>> 
>> On 2020-01-16 21:02, Will Deacon wrote:
>> > [+Jeffrey]
>> >
>> > On Thu, Jan 16, 2020 at 07:49:12PM +0530, Sai Prakash Ranjan wrote:
>> >> KRYO3XX silver CPU cores and KRYO4XX silver, gold CPU cores
>> >> are not affected by Spectre variant 2. Add them to spectre_v2
>> >> safe list to correct ARM_SMCCC_ARCH_WORKAROUND_1 warning and
>> >> vulnerability sysfs value.
>> >>
>> >> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
>> >> ---
>> >>  arch/arm64/include/asm/cputype.h | 6 ++++++
>> >>  arch/arm64/kernel/cpu_errata.c   | 3 +++
>> >>  2 files changed, 9 insertions(+)
>> >>
>> >> diff --git a/arch/arm64/include/asm/cputype.h
>> >> b/arch/arm64/include/asm/cputype.h
>> >> index aca07c2f6e6e..7219cddeba66 100644
>> >> --- a/arch/arm64/include/asm/cputype.h
>> >> +++ b/arch/arm64/include/asm/cputype.h
>> >> @@ -85,6 +85,9 @@
>> >>  #define QCOM_CPU_PART_FALKOR_V1             0x800
>> >>  #define QCOM_CPU_PART_FALKOR                0xC00
>> >>  #define QCOM_CPU_PART_KRYO          0x200
>> >> +#define QCOM_CPU_PART_KRYO_3XX_SILVER       0x803
>> >> +#define QCOM_CPU_PART_KRYO_4XX_GOLD 0x804
>> >> +#define QCOM_CPU_PART_KRYO_4XX_SILVER       0x805
>> >
>> > Jeffrey is the only person I know who understands the CPU naming here,
>> > so
>> > I've added him in case this needs either renaming or extending to cover
>> > other CPUs. I wouldn't be at all surprised if we need a function call
>> > rather than a bunch of table entries...
>> >
>> > That said, the internet claims that KRYO4XX gold is based on
>> > Cortex-A76,
>> > and so CSV2 should be set...
>> >
>> 
>> Yes the internet claims are true and CSV2 is set. SANITY check logs in
>> here show ID_PFR0_EL1 - 
>> https://lore.kernel.org/patchwork/patch/1138457/
> 
> I'm probably just being a noob here and am confused, but if CSV2 is
> set then why do you need your patch at all?  The code I see says that
> if CSV2 is set then we don't even check the spectre_v2_safe_list().
> 

I am a noob here and didn't understand what Will meant ;). V2 posted 
now.

Thanks,
Sai

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