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

From: Will Deacon <will@kernel.org>
To: Doug Anderson <dianders@chromium.org>
Cc: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
	Jeffrey Hugo <jhugo@codeaurora.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Andre Przywara <andre.przywara@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Stephen Boyd <swboyd@chromium.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Matthias Kaehlcke <mka@chromium.org>,
	James Morse <james.morse@arm.com>
Subject: Re: [PATCH] arm64: Add KRYO{3,4}XX CPU cores to spectre-v2 safe list
Date: Thu, 16 Jan 2020 18:31:22 +0000	[thread overview]
Message-ID: <20200116183121.GE22420@willie-the-truck> (raw)
In-Reply-To: <CAD=FV=WP1T7gGC=m5FOwuLvZdwrg5f7K6tDuYFT=0BgCQMZf7A@mail.gmail.com>

On Thu, Jan 16, 2020 at 10:27:08AM -0800, Doug Anderson wrote:
> On Thu, Jan 16, 2020 at 8:11 AM Sai Prakash Ranjan
> <saiprakash.ranjan@codeaurora.org> wrote:
> > On 2020-01-16 21:02, Will Deacon wrote:
> > > 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@codeaurora.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().

You're not being a noob at all -- you're making the same point that I was
trying to make :)

So I think we can take this patch with the KRYO_4XX_GOLD part dropped.

Will