linux-kernel - Re: [PATCH v2 00/18] arm64: Unmap the kernel whilst running in userspace (KAISER)

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Date:   Mon, 4 Dec 2017 15:47:28 -0800
From:   Laura Abbott <labbott@...hat.com>
To:     Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, catalin.marinas@....com,
        mark.rutland@....com, ard.biesheuvel@...aro.org,
        sboyd@...eaurora.org, dave.hansen@...ux.intel.com,
        keescook@...omium.org, msalter@...hat.com, tglx@...utronix.de
Subject: Re: [PATCH v2 00/18] arm64: Unmap the kernel whilst running in
 userspace (KAISER)

On 11/30/2017 08:39 AM, Will Deacon wrote:
> Hi again,
> 
> This is version two of the patches previously posted here:
> 
>    http://lists.infradead.org/pipermail/linux-arm-kernel/2017-November/542751.html
> 
> Changes since v1 include:
> 
>    * Based on v4.15-rc1
>    * Trampoline moved into FIXMAP area
>    * Explicit static key replaced by cpu cap
>    * Disable SPE for userspace profiling if kernel unmapped at EL0
>    * Changed polarity of cpu feature to match config option
>    * Changed command-line option so we can force on in future if necessary
>    * Changed Falkor workaround to invalidate different page within 2MB region
>    * Reworked alternative sequences in entry.S, since the NOP slides with
>      kaiser=off were measurable
> 
> I experimented with leaving the vbar set to point at the kaiser vectors,
> but I couldn't measure any performance improvement from that and it made
> the code slightly more complicated, so I've left it as-is.
> 
> Patches based on 4.15-rc1 and also pushed here:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git kaiser
> 
> Feedback welcome, particularly on a better name for the command-line option.
> 

I ran this with one of the LTP mmap tests over the weekend. The mmap
test completed successfully but later the machine was spewing I/O
errors. I think this is because of the hardware and not the patches
so I'm running again for good measure.

> Will
> 
> --->8
> 
> Will Deacon (18):
>    arm64: mm: Use non-global mappings for kernel space
>    arm64: mm: Temporarily disable ARM64_SW_TTBR0_PAN
>    arm64: mm: Move ASID from TTBR0 to TTBR1
>    arm64: mm: Remove pre_ttbr0_update_workaround for Falkor erratum
>      #E1003
>    arm64: mm: Rename post_ttbr0_update_workaround
>    arm64: mm: Fix and re-enable ARM64_SW_TTBR0_PAN
>    arm64: mm: Allocate ASIDs in pairs
>    arm64: mm: Add arm64_kernel_unmapped_at_el0 helper
>    arm64: mm: Invalidate both kernel and user ASIDs when performing TLBI
>    arm64: entry: Add exception trampoline page for exceptions from EL0
>    arm64: mm: Map entry trampoline into trampoline and kernel page tables
>    arm64: entry: Explicitly pass exception level to kernel_ventry macro
>    arm64: entry: Hook up entry trampoline to exception vectors
>    arm64: erratum: Work around Falkor erratum #E1003 in trampoline code
>    arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native
>      tasks
>    arm64: entry: Add fake CPU feature for unmapping the kernel at EL0
>    arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0
>    perf: arm_spe: Disallow userspace profiling when
>      arm_kernel_unmapped_at_el0()
> 
>   arch/arm64/Kconfig                      |  30 +++--
>   arch/arm64/include/asm/asm-uaccess.h    |  25 +++--
>   arch/arm64/include/asm/assembler.h      |  27 +----
>   arch/arm64/include/asm/cpucaps.h        |   3 +-
>   arch/arm64/include/asm/fixmap.h         |   4 +
>   arch/arm64/include/asm/kernel-pgtable.h |  12 +-
>   arch/arm64/include/asm/mmu.h            |  10 ++
>   arch/arm64/include/asm/mmu_context.h    |   9 +-
>   arch/arm64/include/asm/pgtable-hwdef.h  |   1 +
>   arch/arm64/include/asm/pgtable-prot.h   |  21 +++-
>   arch/arm64/include/asm/pgtable.h        |   1 +
>   arch/arm64/include/asm/proc-fns.h       |   6 -
>   arch/arm64/include/asm/tlbflush.h       |  16 ++-
>   arch/arm64/include/asm/uaccess.h        |  21 +++-
>   arch/arm64/kernel/asm-offsets.c         |   6 +-
>   arch/arm64/kernel/cpufeature.c          |  41 +++++++
>   arch/arm64/kernel/entry.S               | 190 +++++++++++++++++++++++++++-----
>   arch/arm64/kernel/process.c             |  12 +-
>   arch/arm64/kernel/vmlinux.lds.S         |  17 +++
>   arch/arm64/lib/clear_user.S             |   2 +-
>   arch/arm64/lib/copy_from_user.S         |   2 +-
>   arch/arm64/lib/copy_in_user.S           |   2 +-
>   arch/arm64/lib/copy_to_user.S           |   2 +-
>   arch/arm64/mm/cache.S                   |   2 +-
>   arch/arm64/mm/context.c                 |  36 +++---
>   arch/arm64/mm/mmu.c                     |  23 ++++
>   arch/arm64/mm/proc.S                    |  12 +-
>   arch/arm64/xen/hypercall.S              |   2 +-
>   drivers/perf/arm_spe_pmu.c              |   7 ++
>   29 files changed, 407 insertions(+), 135 deletions(-)
>