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Re: [qemu-s390x] [PATCH v1 0/2] s390x/tcg: LAP support using immediate T

From: David Hildenbrand
Subject: Re: [qemu-s390x] [PATCH v1 0/2] s390x/tcg: LAP support using immediate TLB invalidation
Date: Tue, 17 Oct 2017 11:22:19 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0

On 17.10.2017 10:47, Cornelia Huck wrote:
> On Mon, 16 Oct 2017 22:23:56 +0200
> David Hildenbrand <address@hidden> wrote:
>> Details about Low-Address Protection can be found in description of
>> patch 1 and 2. It is basically a subpage protection of the first two
>> pages of every address space (for which it is enabled).
>> We can achieve this by simply directly invalidating the TLB entry and
>> therefore forcing every write accesses onto these two pages into the slow
>> path.
>> With this patch, I can boot Linux just fine (which uses LAP). This also
>> makes all related kvm-unit-tests that we have pass.
> Tested with a kernel based on the s390/features branch (4.14-rc2 + s390
> patches) and the initrd from the debian installer, had udevd shot down
> by the oomkiller. That happened only once, so it was probably an
> unrelated fluke, but that combination worked well before.

Very unlikely, on invalid programming exceptions you would get a kernel
panic, not run oom. (not saying it isn't possible, rather that it is
very unlikely).

Can you reproduce with more memory? Have you enabled SMP? (little higher
memory consumption)

I am running (almost) the same setup with 500M and haven't observed any
such thing.

> [More config data + logs available on request.]

Can you send via (private) mail? I can have a look.

Thanks for testing!




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