linux-kernel - Re: [PATCH v7 2/4] drivers/acpi: Introduce Platform Firmware Runtime Update device driver

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Message-ID: <YX/NwEdw26wzKFvQ@smile.fi.intel.com>
Date:   Mon, 1 Nov 2021 13:21:36 +0200
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     linux-acpi@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>, Len Brown <lenb@...nel.org>,
        Ashok Raj <ashok.raj@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        Aubrey Li <aubrey.li@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/4] drivers/acpi: Introduce Platform Firmware Runtime
 Update device driver

On Mon, Nov 01, 2021 at 05:33:20PM +0800, Chen Yu wrote:
> On Wed, Oct 27, 2021 at 01:20:33PM +0300, Andy Shevchenko wrote:
> > On Wed, Oct 27, 2021 at 03:07:51PM +0800, Chen Yu wrote:

...

> > > +	guid_t *image_type_id = &img_hdr->image_type_id;
> > 
> > efi_guid_t ?
> >
> efi_guid_t is a 32-bit aligned guid_t, which is for the case when
> efi_guid_t* arguments are 32-bit aligned. And it is for 32-bit ARM.
> Since this code injection is only for 64-bit, the guid is not required
> to be strictly 32-bit aligned I suppose?

But the type of that member may not be guid_t. So, I expect not to see guid_t
at all here or as a internal member with the export/import GUID API in place.

See, for example
d1c6e08e7503 ("libnvdimm/labels: Add uuid helpers")

...

> > > +	ret = guid_parse(PFRU_UUID, &pfru_dev->uuid);

> > > +	ret = guid_parse(PFRU_CODE_INJ_UUID, &pfru_dev->code_uuid);

> > > +	ret = guid_parse(PFRU_DRV_UPDATE_UUID, &pfru_dev->drv_uuid);

> > Why do you need to keep zillions of copies of the data which seems
> > is not going to be changed? Three global variables should be enough,
> > no?
> >
> The guid information is embedded in each pfru_dev and only calculated
> once during probe. I thought people try to avoid using global variables
> if possible?

Use your common sense. You might have a lot of data duplication,
and this data is definitely not something that needs any kind of
serialization / personification / etc.

-- 
With Best Regards,
Andy Shevchenko