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AJvYcCWgL+CeE/1f8eVJ1nnD/y3m726crgesfDq5dM4mDitJSHpoKHJyPVIn/Rl3L9YjlB4++wIzRHZZhu4=@lists.xenproject.org X-Gm-Message-State: AOJu0YxDfCasF5amznQKTNdJgGj9jXL2I1lqhangwXPTEGKw2RsMnavC jryW9eiMUkxoobGQCabNo7K2J5w9JBTvj0ZHJdMAA5QkrmPMRERH+PpmZ34scec= X-Google-Smtp-Source: AGHT+IHpisSS5hdtrcYni2bsI5V71NFs1qX4ffPIATmZ/VUELrqZO1ZNSgwaXbeU2ptPCG6al3u76w== X-Received: by 2002:a17:907:7e85:b0:a99:5466:2556 with SMTP id a640c23a62f3a-a9a69cdf7f2mr1286302966b.61.1729505230818; Mon, 21 Oct 2024 03:07:10 -0700 (PDT) Message-ID: <16264b44-f323-48bf-bb03-161effc712eb@citrix.com> Date: Mon, 21 Oct 2024 11:07:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/io-apic: fix directed EOI when using AMd-Vi interrupt remapping To: Alejandro Vallejo , Roger Pau Monne , xen-devel@lists.xenproject.org Cc: Jan Beulich , Willi Junga , David Woodhouse References: <20241018080813.45759-1-roger.pau@citrix.com> Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 21/10/2024 10:55 am, Alejandro Vallejo wrote: > On Fri Oct 18, 2024 at 9:08 AM BST, Roger Pau Monne wrote: >> When using AMD-VI interrupt remapping the vector field in the IO-APIC RTE is >> repurposed to contain part of the offset into the remapping table. Previous to > For my own education. Is that really a repurpose? Isn't the RTE vector field > itself simply remapped, just like any MSI? Yes, it really is repurposed.  The vector field has a different meaning under IR, and indeed different meanings between Intel and AMD. The way you're supposed to use interrupt remapping is to set up a static configuration in the device (inc IO-APIC in this case), and then (only) edit the IO-RTE in the IOMMU to change destination/vector. This avoids needing to do CFG/MMIO cycles to move interrupt affinity, not to mention the corner cases involved with doing so. ~Andrew