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From: Pingfan Liu <kernelfans@gmail.com>
Date: Mon, 16 Mar 2020 16:37:58 +0800
Message-ID: <CAFgQCTvsKaP34_v-P0x_RNDZ2Jne82DMS33LpC5EE819EjhJHg@mail.gmail.com>
Subject: Re: [PATCHv3 2/2] pseries/scm: buffer pmem's bound addr in dt for
 kexec kernel
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
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On Mon, Mar 16, 2020 at 10:53 AM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
>
> On 3/4/20 2:17 PM, Pingfan Liu wrote:
> > At present, plpar_hcall(H_SCM_BIND_MEM, ...) takes a very long time, so
> > if dumping to fsdax, it will take a very long time.
> >
>
>
> that should be fixed by
>
> faa6d21153fd11e139dd880044521389b34a24f2
> Author:       Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> AuthorDate:   Tue Sep 3 18:04:52 2019 +0530
> Commit:       Michael Ellerman <mpe@ellerman.id.au>
> CommitDate:   Wed Sep 25 08:32:59 2019 +1000
>
> powerpc/nvdimm: use H_SCM_QUERY hcall on H_OVERLAP error
>
> Right now we force an unbind of SCM memory at drcindex on H_OVERLAP error.
> This really slows down operations like kexec where we get the H_OVERLAP
> error because we don't go through a full hypervisor re init.
>
> H_OVERLAP error for a H_SCM_BIND_MEM hcall indicates that SCM memory at
> drc index is already bound. Since we don't specify a logical memory
> address for bind hcall, we can use the H_SCM_QUERY hcall to query
> the already bound logical address.
Good to know it.

Thanks,
Pingfan
>
>
>
>
> > Take a closer look, during the papr_scm initialization, the only
> > configuration is through drc_pmem_bind()-> plpar_hcall(H_SCM_BIND_MEM,
> > ...), which helps to set up the bound address.
> >
> > On pseries, for kexec -l/-p kernel, there is no reset of hardware, and this
> > step can be stepped around to save times.  So the pmem bound address can be
> > passed to the 2nd kernel through a dynamic added property "bound-addr" in
> > dt node 'ibm,pmemory'.
> >
>
> -aneesh
>