[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH] xen/arm: Add workaround for Cortex-A76/Neoverse-N1 erratum #1286807


  • To: Michal Orzel <Michal.Orzel@xxxxxxx>
  • From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
  • Date: Mon, 16 Nov 2020 08:47:59 +0000
  • Accept-language: en-GB, en-US
  • Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=arm.com; dmarc=pass action=none header.from=arm.com; dkim=pass header.d=arm.com; arc=none
  • Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=8Gouvb/TiqibQiepFYvSlq32AB6Bh8msCECOWlSjvHI=; b=Q8WXFsdwP6FsdhLW+QChgbU4irr0XwUxRrqJhMgRa1cE21E+BWbh99CFC9X+GdiYP/urYWObpBY0dnNCjc5EDA2mNHbZ+vLDyb6fHqckzkEXRwLJMCp4x59YyC3F+gONUtpbtCgVdOfUu3sWVynImxkl21cuOfAHqPxjhoI6gEXrZkr4JzOAVZPwxKLxWAd8m4riYdYBgltJ9h+hSa/Uxj0eo6quYC0B9BKdl+ul4YL74JyH/n38eDu6O5up2SPGgia32RQ5G20DLN0HLVzgQCv9sgNRCsrZIWfPCX7ze7Z5pLqNynG7iG3ksvAyoBtVRu7Q2fLbT66AXC/3D37fAA==
  • Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=SZ/CA9ppXitjEy1/5kKP4SKbFsyNIyhQ/ytLhQYDXN97V9jC/UAfPhYNTx821WomqT+n/ECFu9rvxYcu3GKHliL3gdWCsp57WELXdktLdsqLp31RFsEWJesvWEk6pJz8Ja4aJ+mi2T2hU1gWyDld8PdN6+B4SaMni42kQnDwAR2p7h0AI2U3NlIvJeZEOE69+uBhk+rKkdMFOKo5Pax4BbAP1WN57MRkfTvhweqVqVrZb2EwewuQ+TFB0ptvGiw5XFHOZRkkAtdOBxdCcG6rWGwKu/hDCfd5uGNdc/t3XmtQ/zK4U4ROfwt7OlyBoH4SbhNrNWdSGDLdkh6/1zzgcg==
  • Authentication-results-original: arm.com; dkim=none (message not signed) header.d=none;arm.com; dmarc=none action=none header.from=arm.com;
  • Cc: "open list:X86" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
  • Delivery-date: Mon, 16 Nov 2020 08:48:32 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Nodisclaimer: true
  • Original-authentication-results: arm.com; dkim=none (message not signed) header.d=none;arm.com; dmarc=none action=none header.from=arm.com;
  • Thread-index: AQHWu+mTw4Xbd+Lh7kKhbnNB05cIaqnKcooA
  • Thread-topic: [PATCH] xen/arm: Add workaround for Cortex-A76/Neoverse-N1 erratum #1286807

Hi,

> On 16 Nov 2020, at 07:24, Michal Orzel <Michal.Orzel@xxxxxxx> wrote:
> 
> On the affected Cortex-A76/Neoverse-N1 cores (r0p0 to r3p0),
> if a virtual address for a cacheable mapping of a location is being
> accessed by a core while another core is remapping the virtual
> address to a new physical page using the recommended break-before-make
> sequence, then under very rare circumstances TLBI+DSB completes before
> a read using the translation being invalidated has been observed by
> other observers. The workaround repeats the TLBI+DSB operation.
> 
> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> docs/misc/arm/silicon-errata.txt     |  2 ++
> xen/arch/arm/Kconfig                 | 18 +++++++++++++++++
> xen/arch/arm/cpuerrata.c             | 14 ++++++++++++++
> xen/include/asm-arm/arm64/flushtlb.h | 29 +++++++++++++++++++---------
> xen/include/asm-arm/cpufeature.h     |  3 ++-
> 5 files changed, 56 insertions(+), 10 deletions(-)
> 
> diff --git a/docs/misc/arm/silicon-errata.txt 
> b/docs/misc/arm/silicon-errata.txt
> index 552c4151d3..d183ba543f 100644
> --- a/docs/misc/arm/silicon-errata.txt
> +++ b/docs/misc/arm/silicon-errata.txt
> @@ -53,5 +53,7 @@ stable hypervisors.
> | ARM            | Cortex-A72      | #853709         | N/A                    
>  |
> | ARM            | Cortex-A73      | #858921         | ARM_ERRATUM_858921     
>  |
> | ARM            | Cortex-A76      | #1165522        | N/A                    
>  |
> +| ARM            | Cortex-A76      | #1286807        | ARM64_ERRATUM_1286807 
>   |
> | ARM            | Neoverse-N1     | #1165522        | N/A
> +| ARM            | Neoverse-N1     | #1286807        | ARM64_ERRATUM_1286807 
>   |
> | ARM            | MMU-500         | #842869         | N/A                    
>  |
> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> index f938dd21bd..5d6d906d72 100644
> --- a/xen/arch/arm/Kconfig
> +++ b/xen/arch/arm/Kconfig
> @@ -244,6 +244,24 @@ config ARM_ERRATUM_858921
> 
>         If unsure, say Y.
> 
> +config ARM64_ERRATUM_1286807
> +     bool "Cortex-A76/Neoverse-N1: 1286807: Modification of the translation 
> table for a virtual address might lead to read-after-read ordering violation"
> +     default y
> +     depends on ARM_64
> +     help
> +       This option adds a workaround for ARM Cortex-A76/Neoverse-N1 erratum 
> 1286807.
> +
> +       On the affected Cortex-A76/Neoverse-N1 cores (r0p0 to r3p0), if a 
> virtual
> +       address for a cacheable mapping of a location is being
> +       accessed by a core while another core is remapping the virtual
> +       address to a new physical page using the recommended
> +       break-before-make sequence, then under very rare circumstances
> +       TLBI+DSB completes before a read using the translation being
> +       invalidated has been observed by other observers. The
> +       workaround repeats the TLBI+DSB operation.
> +
> +       If unsure, say Y.
> +
> endmenu
> 
> config ARM64_HARDEN_BRANCH_PREDICTOR
> diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c
> index 567911d380..cb4795beec 100644
> --- a/xen/arch/arm/cpuerrata.c
> +++ b/xen/arch/arm/cpuerrata.c
> @@ -424,6 +424,20 @@ static const struct arm_cpu_capabilities arm_errata[] = {
>                    (1 << MIDR_VARIANT_SHIFT) | 2),
>     },
> #endif
> +#ifdef CONFIG_ARM64_ERRATUM_1286807
> +    {
> +        /* Cortex-A76 r0p0 - r3p0 */
> +        .desc = "ARM erratum 1286807",
> +        .capability = ARM64_WORKAROUND_REPEAT_TLBI,
> +        MIDR_RANGE(MIDR_CORTEX_A76, 0, 3 << MIDR_VARIANT_SHIFT),
> +    },
> +    {
> +        /* Neoverse-N1 r0p0 - r3p0 */
> +        .desc = "ARM erratum 1286807",
> +        .capability = ARM64_WORKAROUND_REPEAT_TLBI,
> +        MIDR_RANGE(MIDR_NEOVERSE_N1, 0, 3 << MIDR_VARIANT_SHIFT),
> +    },
> +#endif
> #ifdef CONFIG_ARM64_HARDEN_BRANCH_PREDICTOR
>     {
>         .capability = ARM_HARDEN_BRANCH_PREDICTOR,
> diff --git a/xen/include/asm-arm/arm64/flushtlb.h 
> b/xen/include/asm-arm/arm64/flushtlb.h
> index ceec59542e..6726362211 100644
> --- a/xen/include/asm-arm/arm64/flushtlb.h
> +++ b/xen/include/asm-arm/arm64/flushtlb.h
> @@ -9,6 +9,11 @@
>  * DSB ISH          // Ensure the TLB invalidation has completed
>  * ISB              // See explanation below
>  *
> + * ARM64_WORKAROUND_REPEAT_TLBI:
> + * Modification of the translation table for a virtual address might lead to
> + * read-after-read ordering violation.
> + * The workaround repeats TLBI+DSB operation.
> + *
>  * For Xen page-tables the ISB will discard any instructions fetched
>  * from the old mappings.
>  *
> @@ -16,15 +21,21 @@
>  * (and therefore the TLB invalidation) before continuing. So we know
>  * the TLBs cannot contain an entry for a mapping we may have removed.
>  */
> -#define TLB_HELPER(name, tlbop) \
> -static inline void name(void)   \
> -{                               \
> -    asm volatile(               \
> -        "dsb  ishst;"           \
> -        "tlbi "  # tlbop  ";"   \
> -        "dsb  ish;"             \
> -        "isb;"                  \
> -        : : : "memory");        \
> +#define TLB_HELPER(name, tlbop)       \
> +static inline void name(void)         \
> +{                                     \
> +    asm volatile(                     \
> +        "dsb  ishst;"                 \
> +        "tlbi "  # tlbop  ";"         \
> +        ALTERNATIVE(                  \
> +        "nop; nop;",                  \
> +        "dsb  ish;"                   \
> +        "tlbi "  # tlbop  ";",        \
> +        ARM64_WORKAROUND_REPEAT_TLBI, \
> +        CONFIG_ARM64_ERRATUM_1286807) \
> +        "dsb  ish;"                   \
> +        "isb;"                        \
> +        : : : "memory");              \
> }
> 
> /* Flush local TLBs, current VMID only. */
> diff --git a/xen/include/asm-arm/cpufeature.h 
> b/xen/include/asm-arm/cpufeature.h
> index 016a9fe203..c7b5052992 100644
> --- a/xen/include/asm-arm/cpufeature.h
> +++ b/xen/include/asm-arm/cpufeature.h
> @@ -46,8 +46,9 @@
> #define ARM_SMCCC_1_1 8
> #define ARM64_WORKAROUND_AT_SPECULATE 9
> #define ARM_WORKAROUND_858921 10
> +#define ARM64_WORKAROUND_REPEAT_TLBI 11
> 
> -#define ARM_NCAPS           11
> +#define ARM_NCAPS           12
> 
> #ifndef __ASSEMBLY__
> 
> -- 
> 2.28.0
> 




 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.