From: Joao Martins <email@example.com>
To: Pavel Tatashin <firstname.lastname@example.org>
Cc: Dan Williams <email@example.com>,
David Hildenbrand <firstname.lastname@example.org>,
Sasha Levin <email@example.com>,
Tyler Hicks <firstname.lastname@example.org>,
Andrew Morton <email@example.com>,
Michal Hocko <firstname.lastname@example.org>,
Oscar Salvador <email@example.com>,
Vlastimil Babka <firstname.lastname@example.org>,
Joonsoo Kim <email@example.com>,
Jason Gunthorpe <firstname.lastname@example.org>, Marc Zyngier <email@example.com>,
Linux ARM <firstname.lastname@example.org>,
Will Deacon <email@example.com>,
James Morse <firstname.lastname@example.org>,
James Morris <email@example.com>
Subject: Re: dax alignment problem on arm64 (and other achitectures)
Date: Fri, 29 Jan 2021 17:22:38 +0000 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On 1/29/21 4:32 PM, Pavel Tatashin wrote:
> On Fri, Jan 29, 2021 at 9:51 AM Joao Martins <email@example.com> wrote:
>> Hey Pavel,
>> On 1/29/21 1:50 PM, Pavel Tatashin wrote:
>>>> Since we last talked about this the enabling for EFI "Special Purpose"
>>>> / Soft Reserved Memory has gone upstream and instantiates device-dax
>>>> instances for address ranges marked with EFI_MEMORY_SP attribute.
>>>> Critically this way of declaring device-dax removes the consideration
>>>> of it as persistent memory and as such no metadata reservation. So, if
>>>> you are willing to maintain the metadata external to the device (which
>>>> seems reasonable for your environment) and have your platform firmware
>>>> / kernel command line mark it as EFI_CONVENTIONAL_MEMORY +
>>>> EFI_MEMORY_SP, then these reserve-free dax-devices will surface.
>>> Hi Dan,
>>> This is cool. Does it allow conversion between devdax and fsdax so DAX
>>> aware filesystem can be installed and data can be put there to be
>>> preserved across the reboot?
>> fwiw wrt to the 'preserved across kexec' part, you are going to need
>> something conceptually similar to snippet below the scissors mark.
>> Alternatively, we could fix kexec userspace to add conventional memory
>> ranges (without the SP attribute part) when it sees a Soft-Reserved region.
>> But can't tell which one is the right thing to do.
> Hi Joao,
> Is not it just a matter of appending arguments to the kernel parameter
> during kexec reboot with Soft-Reserved region specified, or am I
> missing something? I understand with fileload kexec syscall we might
> accidently load segments onto reserved region, but with the original
> kexec syscall, where we can specify destinations for each segment that
> should not be a problem with today's kexec tools.
efi_fake_mem only works with EFI_MEMMAP conventional memory ranges, thus
not having a EFI_MEMMAP with RAM ranges means it's a nop for the soft-reserved
regions. Unless, you trying to suggest something like:
... To mark soft reserved on top an existing RAM? Sadly don't know if there's
an equivalent for ARM.
> I agree that preserving it automatically as you are proposing, would
> make more sense, instead of fiddling with kernel parameters and
> segment destinations.
> Thank you,
>> At the moment, HMAT ranges (or those defined with efi_fake_mem=) aren't
>> preserved not because of anything special with HMAT, but simply because
>> the EFI memmap conventional ram ranges are not preserved (only runtime
>> services). And HMAT/efi_fake_mem expects these to based on EFI memmap.
next prev parent reply other threads:[~2021-01-29 17:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-27 20:43 dax alignment problem on arm64 (and other achitectures) Pavel Tatashin
2021-01-27 21:09 ` David Hildenbrand
2021-01-27 21:49 ` Pavel Tatashin
2021-01-27 22:18 ` David Hildenbrand
2021-01-27 23:33 ` Pavel Tatashin
2021-01-28 15:03 ` David Hildenbrand
2021-01-29 2:06 ` Pavel Tatashin
[not found] ` <firstname.lastname@example.org>
2021-01-29 16:24 ` Pavel Tatashin
2021-01-29 19:06 ` Pavel Tatashin
2021-01-29 19:12 ` Pavel Tatashin
2021-01-29 19:41 ` Pavel Tatashin
2021-01-29 2:55 ` Dan Williams
[not found] ` <CA+CK2bBJmnTVF8ZfwLyLqgjgo63G-rVQTYwUqgmx8wXFtRH9email@example.com>
[not found] ` <firstname.lastname@example.org>
2021-01-29 16:32 ` Pavel Tatashin
2021-01-29 17:22 ` Joao Martins [this message]
2021-01-29 20:26 ` Dan Williams
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