Re: [PATCH v3 5/6] mm/mmu_gather: invalidate TLB correctly on batch allocation failure and flush

[Greg KH <greg@kroah.com>]

On Thu, Mar 12, 2020 at 06:57:39PM +0530, Santosh Sivaraj wrote:
> From: Peter Zijlstra <peterz@infradead.org>
> 
> commit 0ed1325967ab5f7a4549a2641c6ebe115f76e228 upstream.
> 
> Architectures for which we have hardware walkers of Linux page table
> should flush TLB on mmu gather batch allocation failures and batch flush.
> Some architectures like POWER supports multiple translation modes (hash
> and radix) and in the case of POWER only radix translation mode needs the
> above TLBI.  This is because for hash translation mode kernel wants to
> avoid this extra flush since there are no hardware walkers of linux page
> table.  With radix translation, the hardware also walks linux page table
> and with that, kernel needs to make sure to TLB invalidate page walk cache
> before page table pages are freed.
> 
> More details in commit d86564a2f085 ("mm/tlb, x86/mm: Support invalidating
> TLB caches for RCU_TABLE_FREE")
> 
> The changes to sparc are to make sure we keep the old behavior since we
> are now removing HAVE_RCU_TABLE_NO_INVALIDATE.  The default value for
> tlb_needs_table_invalidate is to always force an invalidate and sparc can
> avoid the table invalidate.  Hence we define tlb_needs_table_invalidate to
> false for sparc architecture.
> 
> Link: http://lkml.kernel.org/r/20200116064531.483522-3-aneesh.kumar@linux.ibm.com
> Fixes: a46cc7a90fd8 ("powerpc/mm/radix: Improve TLB/PWC flushes")
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> Cc: <stable@vger.kernel.org>  # 4.19
> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
> [santosh: backported to 4.19 stable]
> ---
>  arch/Kconfig                    |  3 ---
>  arch/powerpc/Kconfig            |  1 -
>  arch/powerpc/include/asm/tlb.h  | 11 +++++++++++
>  arch/sparc/Kconfig              |  1 -
>  arch/sparc/include/asm/tlb_64.h |  9 +++++++++
>  include/asm-generic/tlb.h       | 15 +++++++++++++++
>  mm/memory.c                     | 16 ++++++++--------
>  7 files changed, 43 insertions(+), 13 deletions(-)

As the testing pointed out, this breaks the build on lots of arches:
	https://lore.kernel.org/r/CAEUSe78+F1Q9LFjpf8SQzQa6+Ak4wcPiiNcUVxEcv+KPdrYvBw@mail.gmail.com
	https://lore.kernel.org/r/cff87cd2-8cd5-241e-3a05-a817b1a56b8c@roeck-us.net

so I'm going to drop this whole series and do a -rc2.

If you still want/need this series in 4.19, please make sure it really
works for everyone :)

thanks,

greg k-h