linux-kernel - Re: [RFC PATCH 0/6] kvm: Growable memory slot array

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 4 Dec 2012 23:48:29 +0900
From:	Takuya Yoshikawa <takuya.yoshikawa@...il.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	mtosatti@...hat.com, kvm@...r.kernel.org, gleb@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/6] kvm: Growable memory slot array

On Mon, 03 Dec 2012 16:39:05 -0700
Alex Williamson <alex.williamson@...hat.com> wrote:

> A couple notes/questions; in the previous version we had a
> kvm_arch_flush_shadow() call when we increased the number of slots.
> I'm not sure if this is still necessary.  I had also made the x86
> specific slot_bitmap dynamically grow as well and switch between a
> direct bitmap and indirect pointer to a bitmap.  That may have
> contributed to needing the flush.  I haven't done that yet here
> because it seems like an unnecessary complication if we have a max
> on the order of 512 or 1024 entries.  A bit per slot isn't a lot of
> overhead.  If we want to go more, maybe we should make it switch.

I have a patch set which removes the slot_bitmap in kvm mmu page
by using reverse mappings for write protecting a memslot.

A bit of concern I still have is the total write protection time
for large memslots.  But since this approach allows us to control
mmu_lock hold time, I think this is a reasonable trade-off.
... and this should be much better than introducing any complication
for slot_bitmap handling.

Thanks,
	Takuya
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/