Messages in this thread |  | | Date | Tue, 4 Feb 2020 19:35:00 +0000 | From | Ashish Kalra <> | Subject | Re: [PATCH v2] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests. |
| |
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. > > >> > >> 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. > > Thanks, > Ashish
|  |