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Mon, 29 Sep 2025 09:19:43 +0000 Message-ID: <02647276-dea2-47b5-a271-7f02666e0492@intel.com> Date: Mon, 29 Sep 2025 17:19:32 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] fs/resctrl,x86/resctrl: Factor mba rounding to be per-arch To: "Luck, Tony" CC: , Reinette Chatre , James Morse , "Thomas Gleixner" , Ingo Molnar , "Borislav Petkov" , Dave Hansen , "H. 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One minor question is that, according to "Figure 6-5. MBA Optimal Bandwidth Register" in the latest RDT specification, the maximum value ranges from 1 to 511. Additionally, this bandwidth field is located at bits 48 to 56 in the MBA Optimal Bandwidth Register, and the range for this segment could be 1 to 8191. Just wonder if it would be possible that the current maximum value of 512 may be extended in the future? Perhaps we could explore a method to query the maximum upper limit from the ACPI table or register, or use CPUID to distinguish between platforms rather than hardcoding it. Reinette also mentioned this in another thread. Thanks, Chenyu [1] https://www.intel.com/content/www/us/en/content-details/851356/intel-resource-director-technology-intel-rdt-architecture-specification.html > The region aware h/w supports separate bandwidth controls for each > region. We could hope (or perhaps update the spec to define) that > region0 is always node-local DDR memory and keep the "MB" tag for > that. > > Then use some other tag naming for other regions. Remote DDR, > local CXL, remote CXL are the ones we think are next in the h/w > memory sequence. But the "region" concept would allow for other > options as other memory technologies come into use. > >> >> Cheers >> ---Dave >