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charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 1/5/22 8:06 AM, Tom Lendacky wrote: > On 1/4/22 4:49 PM, Kirill A. Shutemov wrote: >> Hi Tom, >> >> For larger TDX VM, memset() after set_memory_decrypted() in >> swiotlb_update_mem_attributes() takes substantial portion of boot time. >> >> It makes me wounder why do we need it there? Malicious VMM can mess with >> decrypted/shared buffer at any point and for normal use it will be >> populated with real data anyway. >> >> Can we drop it? > > Probably more a question for Christoph. Does SWIOTLB need to be > initialized to zeroes? If it does, then the memset after the > set_memory_decrypted() is required, otherwise it will appear as ciphertext > to SWIOTLB. > > If I get some time over the next couple of days, I can also try and test > to see what happens. FWIW, I removed the memset() and it doesn't appear to cause any issues. My tests weren't extensive (boot, kernel build, netperf/iperf), though. Thanks, Tom > > Thanks, > Tom > >> _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu