On 7/12/05, Tejun Heo wrote: > Matthew Garrett wrote: > > On boot, Linux will attempt to disable the host protected area on a > > disk. After a suspend/resume cycle, the BIOS may reenable it (seen on a > > Thinkpad T40 and R40). As a result, the kernel is now unable to access > > the HPA. > > > > Is there any issue with just adding a call to idedisk_check_hpa() in the > > IDE resume code? > > This has come up several times now. One thing I'm curious about is > why we are disabling HPA on boot without consent from the user. AFAIK, > HPA is mostly used to implement hidden recovery/suspend storage areas > and disabling automatically on boot increases the likeliness of > destroying them. What do we gain by disabling HPA on boot? Are there > some dumb machines which unnecessarily sets HPA and reduces the capacity > of drives excessively? Even in such cases, wouldn't it be better to do > idedisk_check_hpa() only when kernel parameter explicitly says so? > > -- > tejun
Crawling out from under my rock, I agree with Tejun. Always enabling access to HPA seems very strange. It also eliminates the ability to use the IDE Offset feature. IIUC, the offset feature is a boolean flag that, when true, basically tells the drive that all LBA references are into the HPA area. By using the HPA in conjunction with the Offset flag, one has the ability to have two complete disk layouts. Each could have its own boot sector, partition table, and partitions. I have never used this feature, but I do have DOS based tools that supposidely control the HPA config. and the state of the offset boolean. I routinely perform "forensic image aquires". Normally that is a simple "dd if=/dev/hdx.....". For me the untlimate would be to have Linux support for something like: disable offset dd normal sectors enable offset dd hpa sectors That way I capture the areas as seperate images and if 2 boot sectors, partition tables, partitions etc. exist I can analyse them seperately. Conclusion, automatically overriding HPA seems to be outside of the normal Linux way of doing things. At a minimum, there should be a flag to prevent it from happening. If it is needed there are existing userspace linux tools that can modify the HPA config. FYI: In addition to HPA potentially reducing usable disk size, the size can also be artificially reduced via DCO. I am not aware of any Linux tools for addressing/eliminating artificial DCO restrictions. Greg -- Greg Freemyer The Norcross Group Forensics for the 21st Century - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
