linux-kernel - Re: [PATCH V8 43/44] nvdimm/pmem: Enable stray access protection

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Date:   Fri, 4 Feb 2022 13:10:53 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Weiny, Ira" <ira.weiny@...el.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V8 43/44] nvdimm/pmem: Enable stray access protection

On Thu, Jan 27, 2022 at 9:55 AM <ira.weiny@...el.com> wrote:
>
> From: Ira Weiny <ira.weiny@...el.com>
>
> Now that all valid kernel access' to PMEM have been annotated with
> {__}pgmap_mk_{readwrite,noaccess}() PGMAP_PROTECTION is safe to enable
> in the pmem layer.
>
> Implement the pmem_map_protected() and pmem_mk_{readwrite,noaccess}() to
> communicate this memory has extra protection to the upper layers if
> PGMAP_PROTECTION is specified.
>
> Internally, the pmem driver uses a cached virtual address,
> pmem->virt_addr (pmem_addr).  Use __pgmap_mk_{readwrite,noaccess}()
> directly when PGMAP_PROTECTION is active on the device.
>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
>
> ---
> Changes for V8
>         Rebase to 5.17-rc1
>         Remove global param
>         Add internal structure which uses the pmem device and pgmap
>                 device directly in the *_mk_*() calls.
>         Add pmem dax ops callbacks
>         Use pgmap_protection_available()
>         s/PGMAP_PKEY_PROTECT/PGMAP_PROTECTION
> ---
>  drivers/nvdimm/pmem.c | 52 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 51 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 58d95242a836..2afff8157233 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -138,6 +138,18 @@ static blk_status_t read_pmem(struct page *page, unsigned int off,
>         return BLK_STS_OK;
>  }
>
> +static void __pmem_mk_readwrite(struct pmem_device *pmem)
> +{
> +       if (pmem->pgmap.flags & PGMAP_PROTECTION)
> +               __pgmap_mk_readwrite(&pmem->pgmap);
> +}
> +
> +static void __pmem_mk_noaccess(struct pmem_device *pmem)
> +{
> +       if (pmem->pgmap.flags & PGMAP_PROTECTION)
> +               __pgmap_mk_noaccess(&pmem->pgmap);
> +}
> +

Per previous feedback let's find a way for the pmem driver to stay out
of the loop, and just let these toggles by pgmap generic operations.