From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Barry Silverman" Subject: RE: xen and tls (fwd) Date: Mon, 14 Feb 2005 12:07:36 -0500 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In-Reply-To: Sender: xen-devel-admin@lists.sourceforge.net Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: "Ronald G. Minnich" , Himanshu Raj Cc: xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org As I recall, tls maps negative offsets >0xFF000000 (from segment registers FS, GS) into the kernel address space (IE >0xa8000000), and this conflicts with xen's virtual address mapping. Xen lives mapped into high virtual memory but inaccessible to the guest kernels - however the whole guest kernel address space is accessible to xen. Keir Fraser developed an instruction emulator/code patcher in the page fault code that detected these large offsets from FS/GS, and then fixed them up... I recall that the emulator ended up getting called way for often than anyone wanted and ran slowly. The "not-to-use" TLS recommendation followed from that. Barry Silverman -----Original Message----- From: xen-devel-admin@lists.sourceforge.net [mailto:xen-devel-admin@lists.sourceforge.net]On Behalf Of Ronald G. Minnich Sent: Monday, February 14, 2005 11:53 AM To: Himanshu Raj Cc: xen-devel@lists.sourceforge.net Subject: Re: [Xen-devel] xen and tls (fwd) On Mon, 14 Feb 2005, Himanshu Raj wrote: > I believe it is due to the use of both +ve and -ve offsets by TLS. It becomes > a nightmare to manage it with segmentation, and system has to emulate -ve > offsets by converting to +ve ones etc. I am still learning more on this. I vaguely remember this discussion, I just wish I could remember more. ron ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Xen-devel mailing list Xen-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xen-devel ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click