qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] page fault during ins


From: Mark Williamson
Subject: Re: [Qemu-devel] page fault during ins
Date: Fri, 17 Dec 2004 00:07:15 +0000
User-agent: KMail/1.7.1

> Do we have any device where iomem read changes device state?

It seems like a plausible thing to do, despite seemingly slightly strange 
semantically.

> Wouldn't such hardware cause problems with speculative execution
> (memory reads) on some real CPUs? Or am I missing something?

IO memory regions would have a flag(s) set in the relevant page tables telling 
the CPU that it's not real memory.  This flag would be set by the operating 
system.

This allows the CPU to maintain correct semantics for such devices (not 
reordering writes, not caching reads, etc), whilst still being able to 
optimise accesses to physical RAM aggressively.

Cheers,
Mark




reply via email to

[Prev in Thread] Current Thread [Next in Thread]