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Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, Florian Bezdeka , RT , Mitchell Levy , Michael Kelley , Saurabh Singh Sengar , Naman Jain References: <289d8e52-40f8-4b22-8aa9-d0bd3bd15aae@siemens.com> <20260312170715.HA08BHiO@linutronix.de> <20260317110128.k59TflVp@linutronix.de> <1e15ac0d-9835-487c-9a16-c55203f01a3d@siemens.com> <20260318090817.zuFUjrxd@linutronix.de> From: Jan Kiszka Content-Language: en-US Autocrypt: addr=jan.kiszka@siemens.com; keydata= xsFNBGZY+hkBEACkdtFD81AUVtTVX+UEiUFs7ZQPQsdFpzVmr6R3D059f+lzr4Mlg6KKAcNZ uNUqthIkgLGWzKugodvkcCK8Wbyw+1vxcl4Lw56WezLsOTfu7oi7Z0vp1XkrLcM0tofTbClW xMA964mgUlBT2m/J/ybZd945D0wU57k/smGzDAxkpJgHBrYE/iJWcu46jkGZaLjK4xcMoBWB I6hW9Njxx3Ek0fpLO3876bszc8KjcHOulKreK+ezyJ01Hvbx85s68XWN6N2ulLGtk7E/sXlb 79hylHy5QuU9mZdsRjjRGJb0H9Buzfuz0XrcwOTMJq7e7fbN0QakjivAXsmXim+s5dlKlZjr L3ILWte4ah7cGgqc06nFb5jOhnGnZwnKJlpuod3pc/BFaFGtVHvyoRgxJ9tmDZnjzMfu8YrA +MVv6muwbHnEAeh/f8e9O+oeouqTBzgcaWTq81IyS56/UD6U5GHet9Pz1MB15nnzVcyZXIoC roIhgCUkcl+5m2Z9G56bkiUcFq0IcACzjcRPWvwA09ZbRHXAK/ao/+vPAIMnU6OTx3ejsbHn oh6VpHD3tucIt+xA4/l3LlkZMt5FZjFdkZUuAVU6kBAwElNBCYcrrLYZBRkSGPGDGYZmXAW/ VkNUVTJkRg6MGIeqZmpeoaV2xaIGHBSTDX8+b0c0hT/Bgzjv8QARAQABzSNKYW4gS2lzemth IDxqYW4ua2lzemthQHNpZW1lbnMuY29tPsLBlAQTAQoAPhYhBABMZH11cs99cr20+2mdhQqf QXvYBQJmWPvXAhsDBQkFo5qABQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAAoJEGmdhQqfQXvY zPAP/jGiVJ2VgPcRWt2P8FbByfrJJAPCsos+SZpncRi7tl9yTEpS+t57h7myEKPdB3L+kxzg K3dt1UhYp4FeIHA3jpJYaFvD7kNZJZ1cU55QXrJI3xu/xfB6VhCs+VAUlt7XhOsOmTQqCpH7 pRcZ5juxZCOxXG2fTQTQo0gfF5+PQwQYUp0NdTbVox5PTx5RK3KfPqmAJsBKdwEaIkuY9FbM 9lGg8XBNzD2R/13cCd4hRrZDtyegrtocpBAruVqOZhsMb/h7Wd0TGoJ/zJr3w3WnDM08c+RA 5LHMbiA29MXq1KxlnsYDfWB8ts3HIJ3ROBvagA20mbOm26ddeFjLdGcBTrzbHbzCReEtN++s gZneKsYiueFDTxXjUOJgp8JDdVPM+++axSMo2js8TwVefTfCYt0oWMEqlQqSqgQwIuzpRO6I ik7HAFq8fssy2cY8Imofbj77uKz0BNZC/1nGG1OI9cU2jHrqsn1i95KaS6fPu4EN6XP/Gi/O 0DxND+HEyzVqhUJkvXUhTsOzgzWAvW9BlkKRiVizKM6PLsVm/XmeapGs4ir/U8OzKI+SM3R8 VMW8eovWgXNUQ9F2vS1dHO8eRn2UqDKBZSo+qCRWLRtsqNzmU4N0zuGqZSaDCvkMwF6kIRkD ZkDjjYQtoftPGchLBTUzeUa2gfOr1T4xSQUHhPL8zsFNBGZY+hkBEADb5quW4M0eaWPIjqY6 aC/vHCmpELmS/HMa5zlA0dWlxCPEjkchN8W4PB+NMOXFEJuKLLFs6+s5/KlNok/kGKg4fITf Vcd+BQd/YRks3qFifckU+kxoXpTc2bksTtLuiPkcyFmjBph/BGms35mvOA0OaEO6fQbauiHa QnYrgUQM+YD4uFoQOLnWTPmBjccoPuiJDafzLxwj4r+JH4fA/4zzDa5OFbfVq3ieYGqiBrtj tBFv5epVvGK1zoQ+Rc+h5+dCWPwC2i3cXTUVf0woepF8mUXFcNhY+Eh8vvh1lxfD35z2CJeY txMcA44Lp06kArpWDjGJddd+OTmUkFWeYtAdaCpj/GItuJcQZkaaTeiHqPPrbvXM361rtvaw XFUzUlvoW1Sb7/SeE/BtWoxkeZOgsqouXPTjlFLapvLu5g9MPNimjkYqukASq/+e8MMKP+EE v3BAFVFGvNE3UlNRh+ppBqBUZiqkzg4q2hfeTjnivgChzXlvfTx9M6BJmuDnYAho4BA6vRh4 Dr7LYTLIwGjguIuuQcP2ENN+l32nidy154zCEp5/Rv4K8SYdVegrQ7rWiULgDz9VQWo2zAjo TgFKg3AE3ujDy4V2VndtkMRYpwwuilCDQ+Bpb5ixfbFyZ4oVGs6F3jhtWN5Uu43FhHSCqUv8 FCzl44AyGulVYU7hTQARAQABwsF8BBgBCgAmFiEEAExkfXVyz31yvbT7aZ2FCp9Be9gFAmZY +hkCGwwFCQWjmoAACgkQaZ2FCp9Be9hN3g/8CdNqlOfBZGCFNZ8Kf4tpRpeN3TGmekGRpohU bBMvHYiWW8SvmCgEuBokS+Lx3pyPJQCYZDXLCq47gsLdnhVcQ2ZKNCrr9yhrj6kHxe1Sqv1S MhxD8dBqW6CFe/mbiK9wEMDIqys7L0Xy/lgCFxZswlBW3eU2Zacdo0fDzLiJm9I0C9iPZzkJ gITjoqsiIi/5c3eCY2s2OENL9VPXiH1GPQfHZ23ouiMf+ojVZ7kycLjz+nFr5A14w/B7uHjz uL6tnA+AtGCredDne66LSK3HD0vC7569sZ/j8kGKjlUtC+zm0j03iPI6gi8YeCn9b4F8sLpB lBdlqo9BB+uqoM6F8zMfIfDsqjB0r/q7WeJaI8NKfFwNOGPuo93N+WUyBi2yYCXMOgBUifm0 T6Hbf3SHQpbA56wcKPWJqAC2iFaxNDowcJij9LtEqOlToCMtDBekDwchRvqrWN1mDXLg+av8 qH4kDzsqKX8zzTzfAWFxrkXA/kFpR3JsMzNmvextkN2kOLCCHkym0zz5Y3vxaYtbXG2wTrqJ 8WpkWIE8STUhQa9AkezgucXN7r6uSrzW8IQXxBInZwFIyBgM0f/fzyNqzThFT15QMrYUqhhW ZffO4PeNJOUYfXdH13A6rbU0y6xE7Okuoa01EqNi9yqyLA8gPgg/DhOpGtK8KokCsdYsTbk= In-Reply-To: <20260318090817.zuFUjrxd@linutronix.de> Content-Type: text/plain; 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And that is >> apparently harmless, but fairly confusing. > > correct. My only concern would be a shared handler where the second is > not threaded. The vmbus irqs are not shared (beyond what sysvec_hyperv_callback does). > >>>> With that in mind, the new logic here is no different from the one the >>>> kernel used before. If both are not doing what they should, we likely >>>> want to add a generic reset of hardirq_threaded to the IRQ exit path(s). >>> >>> The difference is that you expect that _everyone_ calling this driver >>> has everything else threaded. This might not be the case. That is why >>> this should be in core knowing what is called if threaded, use in driver >>> after explicit killing that flag afterwards since you don't know what >>> can follow or add a generic threaded infrastructure here. >> >> This driver is different, unfortunately. I'm not sure if we can / want >> to thread everything that the platform interrupt does on x86. So far, >> only the last part of it - vmbus handling - is threaded. On arm64, the >> irq is exclusive (see vmbus_percpu_isr), thus everything can be and is >> threaded. > > No, it is a percpu interrupt which are not forced-threaded. It is threaded now due to my patch. > >>>>> Couldn't the whole logic be integrated into the IRQ code? Then we could >>>>> have mask/ unmask if supported/ provided and threaded interrupts. Then >>>>> sysvec_hyperv_reenlightenment() could use a proper threaded interrupt >>>>> instead apic_eoi() + schedule_delayed_work(). >>>>> >>>> >>>> Again, you are thinking x86-only. We need a portable solution. >>> >>> well, ARM could use a threaded interrupt, too. >> >> For a reason we didn't explore in details, per-CPU interrupts aren't >> threaded. See older version of this patch >> (https://lore.kernel.org/lkml/005a01dc9d30$a40515e0$ec0f41a0$@zohomail.com/) >> where I thought I only had to fix x86, but arm64 was needing care as well. > > Per-CPU are usually timers or other things which are not threaded and > have their own thing for the "second" port and I only remember MCE using > a workqueue for notification. And the hv vmbus now provides a case where threading could be useful, at least for arm64. For x86, we would have to check if the first half of sysvec_hyperv_callback (mshv_handler) wants threading as well / would support that. Jan -- Siemens AG, Foundational Technologies Linux Expert Center