From: Mikulas Patocka <mpatocka@redhat.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Robin Murphy <robin.murphy@arm.com>,
Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
Joao Pinto <Joao.Pinto@synopsys.com>,
linux-pci <linux-pci@vger.kernel.org>,
Jingoo Han <jingoohan1@gmail.com>,
Will Deacon <will.deacon@arm.com>,
Russell King <linux@armlinux.org.uk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Matt Sealey <neko@bakuhatsu.net>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: framebuffer corruption due to overlapping stp instructions on arm64
Date: Mon, 6 Aug 2018 15:54:33 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1808061552090.11930@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <CAKv+Gu_8Rq6X24ZOYvG7+kQQGSGYAZuu_co4k1nJS8K7rkrWMA@mail.gmail.com>
On Mon, 6 Aug 2018, Ard Biesheuvel wrote:
> On 6 August 2018 at 19:09, Mikulas Patocka <mpatocka@redhat.com> wrote:
> >
> >
> > On Mon, 6 Aug 2018, Ard Biesheuvel wrote:
> >
> >> On 6 August 2018 at 14:42, Robin Murphy <robin.murphy@arm.com> wrote:
> >> > On 06/08/18 11:25, Mikulas Patocka wrote:
> >> > [...]
> >> >>>
> >> >>> None of this explains why some transactions fail to make it across
> >> >>> entirely. The overlapping writes in question write the same data to
> >> >>> the memory locations that are covered by both, and so the ordering in
> >> >>> which the transactions are received should not affect the outcome.
> >> >>
> >> >>
> >> >> You're right that the corruption couldn't be explained just by reordering
> >> >> writes. My hypothesis is that the PCIe controller tries to disambiguate
> >> >> the overlapping writes, but the disambiguation logic was not tested and it
> >> >> is buggy. If there's a barrier between the overlapping writes, the PCIe
> >> >> controller won't see any overlapping writes, so it won't trigger the
> >> >> faulty disambiguation logic and it works.
> >> >>
> >> >> Could the ARM engineers look if there's some chicken bit in Cortex-A72
> >> >> that could insert barriers between non-cached writes automatically?
> >> >
> >> >
> >> > I don't think there is, and even if there was I imagine it would have a
> >> > pretty hideous effect on non-coherent DMA buffers and the various other
> >> > places in which we have Normal-NC mappings of actual system RAM.
> >> >
> >>
> >> Looking at the A72 manual, there is one chicken bit that looks like it
> >> may be related:
> >>
> >> CPUACTLR_EL1 bit #50:
> >>
> >> 0 Enables store streaming on NC/GRE memory type. This is the reset value.
> >> 1 Disables store streaming on NC/GRE memory type.
> >>
> >> so putting something like
> >>
> >> mrs x0, S3_1_C15_C2_0
> >> orr x0, x0, #(1 << 50)
> >> msr S3_1_C15_C2_0, x0
> >>
> >> in __cpu_setup() would be worth a try.
> >
> > It won't boot.
> >
> > But if i write the same value that was read, it also won't boot.
> >
> > I created a simple kernel module that reads this register and it has bit
> > 32 set, all other bits clear. But when I write the same value into it, the
> > core that does the write is stuck in infinite loop.
> >
> > So, it seems that we are writing this register from a wrong place.
> >
>
> Ah, my bad. I didn't look closely enough at the description:
>
> """
> The accessibility to the CPUACTLR_EL1 by Exception level is:
>
> EL0 -
> EL1(NS) RW (a)
> EL1(S) RW (a)
> EL2 RW (b)
> EL3(SCR.NS = 1) RW
> EL3(SCR.NS = 0) RW
>
> (a) Write access if ACTLR_EL3.CPUACTLR is 1 and ACTLR_EL2.CPUACTLR is
> 1, or ACTLR_EL3.CPUACTLR is 1 and SCR.NS is 0.
> """
>
> so you'll have to do this from ARM Trusted Firmware. If you're
> comfortable rebuilding that:
>
> diff --git a/include/lib/cpus/aarch64/cortex_a72.h
> b/include/lib/cpus/aarch64/cortex_a72.h
> index bfd64918625b..a7b8cf4be0c6 100644
> --- a/include/lib/cpus/aarch64/cortex_a72.h
> +++ b/include/lib/cpus/aarch64/cortex_a72.h
> @@ -31,6 +31,7 @@
> #define CORTEX_A72_ACTLR_EL1 S3_1_C15_C2_0
>
> #define CORTEX_A72_ACTLR_DISABLE_L1_DCACHE_HW_PFTCH (1 << 56)
> +#define CORTEX_A72_ACTLR_DIS_NC_GRE_STORE_STREAMING (1 << 50)
> #define CORTEX_A72_ACTLR_NO_ALLOC_WBWA (1 << 49)
> #define CORTEX_A72_ACTLR_DCC_AS_DCCI (1 << 44)
> #define CORTEX_A72_ACTLR_EL1_DIS_INSTR_PREFETCH (1 << 32)
> diff --git a/lib/cpus/aarch64/cortex_a72.S b/lib/cpus/aarch64/cortex_a72.S
> index 55e508678284..5914d6ee3ba6 100644
> --- a/lib/cpus/aarch64/cortex_a72.S
> +++ b/lib/cpus/aarch64/cortex_a72.S
> @@ -133,6 +133,15 @@ func cortex_a72_reset_func
> orr x0, x0, #CORTEX_A72_ECTLR_SMP_BIT
> msr CORTEX_A72_ECTLR_EL1, x0
> isb
> +
> + /* ---------------------------------------------
> + * Disables store streaming on NC/GRE memory type.
> + * ---------------------------------------------
> + */
> + mrs x0, CORTEX_A72_ACTLR_EL1
> + orr x0, x0, #CORTEX_A72_ACTLR_DIS_NC_GRE_STORE_STREAMING
> + msr CORTEX_A72_ACTLR_EL1, x0
> + isb
> ret x19
> endfunc cortex_a72_reset_func
Unfortunatelly, it doesn't work. I verified that the bit is set after
booting Linux, but the memcpy corruption was still present.
I also tried the other chicken bits, it slowed down the system noticeably,
but had no effect on the memcpy corruption.
Mikulas
next prev parent reply other threads:[~2018-08-06 19:54 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-02 19:31 framebuffer corruption due to overlapping stp instructions on arm64 Mikulas Patocka
[not found] ` <CAHCPf3tFGqkYEcWNN4LaWThw_rVqT316pzLv6T7RfxwO-eZ0EA@mail.gmail.com>
2018-08-03 6:35 ` Mikulas Patocka
2018-08-03 7:16 ` Ard Biesheuvel
2018-08-03 9:41 ` Will Deacon
2018-08-03 17:09 ` Mikulas Patocka
2018-08-03 17:32 ` Sinan Kaya
2018-08-03 17:33 ` Ard Biesheuvel
2018-08-03 18:25 ` Mikulas Patocka
2018-08-03 20:44 ` Matt Sealey
2018-08-03 21:20 ` Ard Biesheuvel
2018-08-06 10:25 ` Mikulas Patocka
2018-08-06 12:42 ` Robin Murphy
2018-08-06 12:53 ` Ard Biesheuvel
2018-08-06 13:41 ` Marcin Wojtas
2018-08-06 13:48 ` Ard Biesheuvel
2018-08-06 14:07 ` Marcin Wojtas
2018-08-06 14:13 ` Mikulas Patocka
2018-08-06 15:47 ` Ard Biesheuvel
2018-08-06 17:09 ` Mikulas Patocka
2018-08-06 17:21 ` Ard Biesheuvel
2018-08-06 19:54 ` Mikulas Patocka [this message]
2018-08-06 20:11 ` Ard Biesheuvel
2018-08-06 20:31 ` Mikulas Patocka
2018-08-07 16:40 ` Marcin Wojtas
2018-08-07 17:39 ` Mikulas Patocka
2018-08-07 18:07 ` Ard Biesheuvel
2018-08-07 18:17 ` Mikulas Patocka
[not found] ` <CAPv3WKcKoEe=Qysp6Oac2C=G9bUhUQf1twSRCY+_qJ6XEC-iag@mail.gmail.com>
2018-08-08 14:10 ` Mikulas Patocka
2018-08-06 17:13 ` Catalin Marinas
2018-08-06 17:19 ` Mikulas Patocka
2018-08-08 18:31 ` Mikulas Patocka
2018-08-04 13:29 ` Mikulas Patocka
2018-08-08 12:16 ` Catalin Marinas
2018-08-08 13:02 ` David Laight
2018-08-08 13:46 ` Mikulas Patocka
2018-08-08 14:26 ` David Laight
2018-08-08 14:50 ` Catalin Marinas
2018-08-08 16:21 ` Mikulas Patocka
2018-08-08 16:31 ` Arnd Bergmann
2018-08-08 16:43 ` David Laight
2018-08-08 18:56 ` Mikulas Patocka
2018-08-08 18:37 ` Mikulas Patocka
2018-08-08 11:39 ` Catalin Marinas
2018-08-08 14:12 ` Mikulas Patocka
2018-08-08 14:28 ` Catalin Marinas
2018-08-08 18:40 ` Mikulas Patocka
2018-08-08 15:01 ` Richard Earnshaw (lists)
2018-08-08 15:14 ` Catalin Marinas
2018-08-08 16:01 ` Arnd Bergmann
2018-08-08 18:25 ` Mikulas Patocka
2018-08-08 21:51 ` Arnd Bergmann
2018-08-09 15:29 ` Arnd Bergmann
2018-08-03 7:11 ` Andrew Pinski
2018-08-03 7:53 ` Florian Weimer
2018-08-03 9:12 ` Szabolcs Nagy
2018-08-03 9:15 ` Ramana Radhakrishnan
2018-08-03 9:29 ` Ard Biesheuvel
2018-08-03 9:37 ` Ramana Radhakrishnan
2018-08-03 9:42 ` Richard Earnshaw (lists)
2018-08-04 0:58 ` Mikulas Patocka
2018-08-04 1:13 ` Andrew Pinski
2018-08-04 11:04 ` Mikulas Patocka
2018-08-05 18:33 ` Florian Weimer
2018-08-06 8:02 ` Mikulas Patocka
2018-08-06 8:10 ` Ard Biesheuvel
2018-08-06 10:31 ` Mikulas Patocka
2018-08-06 10:37 ` Ard Biesheuvel
2018-08-06 10:42 ` Mikulas Patocka
2018-08-06 10:48 ` Ard Biesheuvel
2018-08-06 12:09 ` Mikulas Patocka
2018-08-06 12:19 ` Ard Biesheuvel
2018-08-06 12:22 ` Ard Biesheuvel
2018-08-07 14:14 ` Mikulas Patocka
2018-08-07 14:40 ` Ard Biesheuvel
2018-08-08 19:15 ` Mikulas Patocka
2018-08-06 11:19 ` Siddhesh Poyarekar
2018-08-06 11:29 ` Ard Biesheuvel
2018-08-06 14:26 ` Tulio Magno Quites Machado Filho
2018-08-05 21:51 ` Pavel Machek
2018-08-06 14:30 ` Mikulas Patocka
2018-08-03 11:24 ` David Laight
2018-08-03 12:04 ` Mikulas Patocka
2018-08-03 13:04 ` David Laight
2018-08-05 14:36 ` Mikulas Patocka
2018-08-06 10:18 ` David Laight
2018-08-07 14:07 ` Mikulas Patocka
2018-08-07 14:33 ` David Laight
2018-08-08 14:21 ` Mikulas Patocka
2018-08-03 13:20 ` Mikulas Patocka
2018-08-03 13:31 ` Mikulas Patocka
2018-08-03 14:17 ` Richard Earnshaw (lists)
2018-08-05 21:36 ` Pavel Machek
2018-08-06 8:04 ` Ramana Radhakrishnan
2018-08-06 8:44 ` Pavel Machek
2018-08-06 9:11 ` Ard Biesheuvel
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