Hello Konrad, On Tue, Mar 03, 2020 at 12:03:53PM -0500, Konrad Rzeszutek Wilk wrote: > On Tue, Feb 04, 2020 at 07:35:00PM +0000, Ashish Kalra wrote: > > Hello Konrad, > > > > Looking fwd. to your feedback regarding support of other memory > > encryption architectures such as Power, S390, etc. > > > > Thanks, > > Ashish > > > > On Fri, Jan 24, 2020 at 11:00:08PM +0000, Ashish Kalra wrote: > > > On Tue, Jan 21, 2020 at 03:54:03PM -0500, Konrad Rzeszutek Wilk wrote: > > > > > > > > > > Additional memory calculations based on # of PCI devices and > > > > > their memory ranges will make it more complicated with so > > > > > many other permutations and combinations to explore, it is > > > > > essential to keep this patch as simple as possible by > > > > > adjusting the bounce buffer size simply by determining it > > > > > from the amount of provisioned guest memory. > > > >> > > > >> Please rework the patch to: > > > >> > > > >> - Use a log solution instead of the multiplication. > > > >> Feel free to cap it at a sensible value. > > > > > > Ok. > > > > > > >> > > > >> - Also the code depends on SWIOTLB calling in to the > > > >> adjust_swiotlb_default_size which looks wrong. > > > >> > > > >> You should not adjust io_tlb_nslabs from swiotlb_size_or_default. > > > > > > >> That function's purpose is to report a value. > > > >> > > > >> - Make io_tlb_nslabs be visible outside of the SWIOTLB code. > > > >> > > > >> - Can you utilize the IOMMU_INIT APIs and have your own detect which > > > >> would > > > >> modify the io_tlb_nslabs (and set swiotbl=1?). > > > > > > This seems to be a nice option, but then IOMMU_INIT APIs are > > > x86-specific and this swiotlb buffer size adjustment is also needed > > > for other memory encryption architectures like Power, S390, etc. > > Oh dear. That I hadn't considered. > > > > > > >> > > > >> Actually you seem to be piggybacking on pci_swiotlb_detect_4gb - so > > > >> perhaps add in this code ? Albeit it really should be in it's own > > > >> file, not in arch/x86/kernel/pci-swiotlb.c > > > > > > Actually, we piggyback on pci_swiotlb_detect_override which sets > > > swiotlb=1 as x86_64_start_kernel() and invocation of sme_early_init() > > > forces swiotlb on, but again this is all x86 architecture specific. > > Then it looks like the best bet is to do it from within swiotlb_init? > We really can't do it from swiotlb_size_or_default - that function > should just return a value and nothing else. >
Actually, we need to do it in swiotlb_size_or_default() as this gets called by reserve_crashkernel_low() in arch/x86/kernel/setup.c and used to reserve low crashkernel memory. If we adjust swiotlb size later in swiotlb_init() which gets called later than reserve_crashkernel_low(), then any swiotlb size changes/expansion will conflict/overlap with the low memory reserved for crashkernel. Thanks, Ashish _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
