Arjan van de Ven wrote:
On Tue, 2006-07-18 at 00:00 -0700, Chris Wright wrote:
plain text document attachment (i386-cpuid)
Allow subarchitectures to modify the CPUID instruction. This allows
the subarch to provide a limited set of CPUID feature flags during CPU
identification. Add a subarch implementation for Xen that traps to the
hypervisor where unsupported feature flags can be hidden from guests.
Hi,
I'm wondering if this is entirely the wrong level of abstraction; to me
it feels the subarch shouldn't override the actual cpuid, but the cpu
feature flags that linux uses. That's a lot less messy: cpuid has many
many pieces of information which are near impossible to filter in
practice, however filtering the USAGE of it is trivial; linux basically
flattens the cpuid namespace into a simple bitmap of "what the kernel
can use". That is really what the subarch should filter/fixup, just like
we do for cpu quirks etc etc.
You really need a CPUID hook. The instruction is non-virtualizable, and
anything claiming to be a hypervisor really has to support masking and
flattening the cpuid namespace for the instruction itself. It is used
in assembler code and very early in boot. The alternative is injecting
a bunch of Xen-specific code to filter feature bits into the i386 layer,
which is both bad for Linux and bad for Xen - and was quite ugly in the
last set of Xen patches.
Zach
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
