linux-kernel - Re: [PATCH v3 08/14] x86, dax, libnvdimm: move wb_cache

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Date:   Thu, 15 Jun 2017 10:11:24 +0200
From:   Jan Kara <jack@...e.cz>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Jan Kara <jack@...e.cz>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        dm-devel@...hat.com, Matthew Wilcox <mawilcox@...rosoft.com>,
        X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>, Jeff Moyer <jmoyer@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH v3 08/14] x86, dax, libnvdimm: move wb_cache_pmem() to
 libnvdimm

On Wed 14-06-17 09:49:29, Dan Williams wrote:
> On Wed, Jun 14, 2017 at 3:54 AM, Jan Kara <jack@...e.cz> wrote:
> >> -/**
> >> - * arch_wb_cache_pmem - write back a cache range with CLWB
> >> - * @vaddr:   virtual start address
> >> - * @size:    number of bytes to write back
> >> - *
> >> - * Write back a cache range using the CLWB (cache line write back)
> >> - * instruction. Note that @size is internally rounded up to be cache
> >> - * line size aligned.
> >> - */
> >>  static inline void arch_wb_cache_pmem(void *addr, size_t size)
> >>  {
> >> -     u16 x86_clflush_size = boot_cpu_data.x86_clflush_size;
> >> -     unsigned long clflush_mask = x86_clflush_size - 1;
> >> -     void *vend = addr + size;
> >> -     void *p;
> >> -
> >> -     for (p = (void *)((unsigned long)addr & ~clflush_mask);
> >> -          p < vend; p += x86_clflush_size)
> >> -             clwb(p);
> >> +     clean_cache_range(addr,size);
> >>  }
> >
> > So this will make compilation break on 32-bit x86 as it does not define
> > clean_cache_range(). Do we somewhere force we are on x86_64 when pmem is
> > enabled?
> 
> Yes, this is enforced by:
> 
>     select ARCH_HAS_PMEM_API if X86_64
> 
> ...in arch/x86/Kconfig. We fallback to a dummy arch_wb_cache_pmem()
> implementation and emit this warning for !ARCH_HAS_PMEM_API archs:
> 
>     "nd_pmem namespace0.0: unable to guarantee persistence of writes"

Aha, right. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

							Honza

-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR