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From: Kenneth Merry <ken@plutotech.com>
Message-Id: <199710210517.XAA18704@pluto.plutotech.com>
Subject: Re: user vm addr to kernel vm addr
In-Reply-To: <199710210201.UAA10419@pluto.plutotech.com> from Mike Durian at "Oct 20, 97 08:01:11 pm"
To: durian@plutotech.com (Mike Durian)
Date: Mon, 20 Oct 1997 23:17:20 -0600 (MDT)
Cc: hackers@FreeBSD.ORG
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Mike Durian wrote...
>   In my virtual file system I'd like to speed up reads and writes
> by copying directly from the uio structure to a vm address of
> a buffer in the user process running on behalf of the filesystem.
> I'm currently shoving all the data through a socket that the
> user process reads from and copies into a buffer.  I'd like to
> go direct and skip the socket writing part.  Does that make sense?
>   Anyway, I want to copy from a uio to a different process's vm space.
> I can get the vm address of the destination buffer over a socket and
> think I can use vm_fault_wire to make sure it stays accessable, but
> I don't know how to convert that user space vm address into a
> kernel space vm address that I can then use with copyout.
>   Is there an easy (or any) way to do this?

	I'm not positive this is what you're looking for, but... one way 
to do it is to map the user address into the kernel address space using 
vmapbuf().

	If you want a specific code example, just let me know.  (or look in
the CAM SCSI passthrough driver for the passmapmem() and passunmapmem()
functions)


Ken
-- 
Kenneth Merry
ken@plutotech.com