Re: [Tails-dev] from sdmem to memtest, and testing procedure…

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Autor: Maxim Kammerer
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Dla: intrigeri
CC: The Tails public development discussion list
Temat: Re: [Tails-dev] from sdmem to memtest, and testing procedures
Hi,

> as far as Tails is concerned, I'm thinking of:
>  - on 64-bit hardware, kexec to a 64-bit kernel and use memtest=
>    there; Maxim, have you confirmed by actual testing this works for
>    more than 3GB?


I have confirmed that KEXEC-ing from 32-bit kernel into 64-bit one
works, and that memtest covered all of 1.5 GiB that QEMU was provided
with, but since it's 64-bit kernel with no concept of high memory, I
doubt there is any actual limit.

>  - on 32-bit hardware, kexec to a 32-bit kernel and go on using
>    sdmem; it's still limited to 3GB, but arguably 32-bit computers
>    with more than 3GB of RAM are very rare.


See my other email — you can use 1G/3G VMSPLIT in the 32-bit KEXEC
kernel, and cover a bit less than 3 GiB with memtest. I tested with
1.5 GiB, and memtest covered all of it. Running without memtest (so
that QEMU doesn't try to use the allocated memory) with 3 GiB RAM,
LOWMEM is 2939 MiB, and HIGHMEM 131 MiB — so it's the previous ~895
MiB we've seen + added 2 GiB due to changed VMSPLIT. To summarize,
using memtest + 1G/3G VMSPLIT is comparabled to sdmem (~130 MiB less),
but likely more robust. And I agree that one would need to try very
hard in order to find 32-bit CPUs with more than even 2 GiB on
motherboard.

Best regards,
Maxim

--
Maxim Kammerer
Liberté Linux (discussion / support: http://dee.su/liberte-contribute)