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Message-ID: <CAPcyv4hg=CGMCopRnxNdB33yJ0E9qpyyYQUix0yh2KtS_kFzgw@mail.gmail.com>
Date: Thu, 14 Jul 2016 22:24:32 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: "Lee, Chun-Yi" <joeyli.kernel@...il.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Linda Knippers <linda.knippers@....com>,
"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
Linux ACPI <linux-acpi@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Lee, Chun-Yi" <jlee@...e.com>, Gary Lin <GLin@...e.com>
Subject: Re: [PATCH v4] acpi, nfit: treat virtual ramdisk SPA as pmem region
On Thu, Jul 14, 2016 at 9:05 PM, Lee, Chun-Yi <joeyli.kernel@...il.com> wrote:
> This patch adds logic to treat virtual ramdisk SPA as pmem region, then
> ramdisk's /dev/pmem* device can be mounted with iso9660.
>
> It's useful to work with the httpboot in EFI firmware to pull a remote
> ISO file to the local memory region for booting and installation.
>
> Wiki page of UEFI HTTPBoot with OVMF:
> https://en.opensuse.org/UEFI_HTTPBoot_with_OVMF
>
> The ramdisk function in EDK2/OVMF generates a ACPI0012 root device that
> it contains empty _STA but without _DSM:
>
> DefinitionBlock ("ssdt2.aml", "SSDT", 2, "INTEL ", "RamDisk ", 0x00001000)
> {
> Scope (\_SB)
> {
> Device (NVDR)
> {
> Name (_HID, "ACPI0012") // _HID: Hardware ID
> Name (_STR, Unicode ("NVDIMM Root Device")) // _STR: Description String
> Method (_STA, 0, NotSerialized) // _STA: Status
> {
> Return (0x0F)
> }
> }
> }
> }
>
> In section 5.2.25.2 of ACPI 6.1 spec, it mentions that the "SPA Range
> Structure Index" of virtual SPA shall be set to zero. That means virtual SPA
> will not be associated by any NVDIMM region mapping.
>
> The VCD's SPA Range Structure in NFIT is similar to virtual disk region
> as following:
>
> [028h 0040 2] Subtable Type : 0000 [System Physical Address Range]
> [02Ah 0042 2] Length : 0038
>
> [02Ch 0044 2] Range Index : 0000
> [02Eh 0046 2] Flags (decoded below) : 0000
> Add/Online Operation Only : 0
> Proximity Domain Valid : 0
> [030h 0048 4] Reserved : 00000000
> [034h 0052 4] Proximity Domain : 00000000
> [038h 0056 16] Address Range GUID : 77AB535A-45FC-624B-5560-F7B281D1F96E
> [048h 0072 8] Address Range Base : 00000000B6ABD018
> [050h 0080 8] Address Range Length : 0000000005500000
> [058h 0088 8] Memory Map Attribute : 0000000000000000
>
> The way to not associate a SPA range is to never reference it from a "flush hint",
> "interleave", or "control region" table.
>
> After testing on OVMF, pmem driver can support the region that it doesn't
> assoicate to any NVDIMM mapping. So, treat VCD like pmem is a idea to get
> a pmem block device that it contains iso.
>
> v4:
> Instoduce nfit_spa_is_virtual() to check virtual ramdisk SPA and create
> pmem region.
>
> v3:
> To simplify patch, removed useless VCD region in libnvdimm.
>
> v2:
> Removed the code for setting VCD to a read-only region.
>
> Cc: Gary Lin <GLin@...e.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Linda Knippers <linda.knippers@....com>
> Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
Applied, thanks.
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