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Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit check
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2 |
Date: |
Mon, 14 Jul 2008 12:11:49 +0100 |
User-agent: |
KMail/1.9.9 |
> Some 32-bit guests effectively disable segment range calculations
> checks by setting the maximum limit and zero offset. Apparently, this
> is faster on some real CPUs too.
>
> Could type checking be done at translation time, including the segment
> types in the translation cache key?
Maybe. If we have a spare hflags bit you could probably use that to indicate
whether segment limit checks are needed.
> For guests like older Linux, with zero base and non-maximum limit in
> user mode, could limit checking be done by the MMU TLB instead?
Not really. The only resonable way to do this would be to use a very large
virtual address space, with the high bits being the segment descriptor. This
might work for 32-bit targets on 64-bit hosts, but even then it's liable to
be more pain than it's worth.
Paul
- [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks, Jan Kiszka, 2008/07/09
- [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2, Jan Kiszka, 2008/07/14
- Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2, Jamie Lokier, 2008/07/14
- Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2,
Paul Brook <=
- Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2, Jamie Lokier, 2008/07/14
- Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2, Kevin O'Connor, 2008/07/14
- Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2, Jamie Lokier, 2008/07/14
- [Qemu-devel] Re: [RFC][PATCH] x86: Optional segment type and limit checks - v2, Jan Kiszka, 2008/07/15
- Re: [Qemu-devel] Re: [RFC][PATCH] x86: Optional segment type and limit checks - v2, Jamie Lokier, 2008/07/15
- Re: [Qemu-devel] Re: [RFC][PATCH] x86: Optional segment type and limit checks - v2, Kevin O'Connor, 2008/07/15
- Re: [Qemu-devel] Re: [RFC][PATCH] x86: Optional segment type and limit checks - v2, Kevin O'Connor, 2008/07/15
Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2, Daniel P. Berrange, 2008/07/14