On Friday 15 November 2013 09:20 AM, Russell King - ARM Linux wrote: > On Thu, Nov 14, 2013 at 02:37:43PM -0500, Santosh Shilimkar wrote: >> Slab allocator can allocate memory beyond the lowmem watermark >> which can lead to false failure of virt_addr_valid(). > > This is definitely going to cause problems. > >> So drop the check. The issue was seen with percpu_alloc() >> in KVM code which was allocating memory beyond lowmem watermark. >> >> Am not completly sure whether this is the right fix and if it could >> impact any other user of virt_addr_valid(). Without this fix as >> pointed out the KVM init was failing in my testing. > > virt_addr_valid() gets used in some places to check whether the virtual > address is part of the lowmem mapping and explicitly not part of vmalloc() > or DMA coherent space: > > drivers/mtd/nand/gpmi-nand/gpmi-nand.c > drivers/net/wireless/ath/ath6kl/sdio.c > > It opens up the checks in include/linux/scatterlist.h to start accepting > non-streaming DMA capable buffers as well. > > It also bypasses a check in the slab code to ensure that it's a potentially > valid pointer that was handed out by slab. > Thanks for the additional information Russell. We are going with an alternate approach from Marc so this patch will be dropped any ways. Regards, Santosh _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
