From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. J. Lu" Date: Wed, 22 Oct 2003 22:47:13 +0000 Subject: Re: make X server on zx2000 (and probably others) work again Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Tue, Oct 21, 2003 at 05:59:58PM -0700, David Mosberger wrote: > In recent 2.5/6 kernels, the X server on my zx2000/Radeon workstation > would cause a crash. Turns out this is due to a long-standing bug in > efi.c: the range checking in efi_mem_type() and efi_mem_attributes() > could cause an underflow if the size of a memory descriptor is zero > (as happens sometimes due to memory trimming). In my case, granule > zero had a zero size and that in turn caused all /dev/mem mappings to > occur with WRITE-BACK mapping, which doesn't make the X server happy > (instant MCA on a zx2000, for example). > > Note that this bug existed for a long time, so it's possible that > there may have been other subtle memory-attribute related problems in > the past. This bug just became more noticable recently, since the > /dev/mem driver now completely ignores the O_SYNC flag and relies > totally on the value returned by efi_mem_attributes(). > I have a very strange problem with my bigsur. Whenever I put a new kernel on it, it would crash at random without any warnings during boot after a warm reboot. I had to power cycle it to get it to boot. After applying this patch to 2.4.21, I have rebooted it twice without powering it down first. H.J.