arch/arm64: Optimized SGI to avoid VM exit. #14689
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In the virtualized environment, each time an SGI is sent, the value of IGROUPR0 needs to be read once. Since the GIC Redistributor is a purely emulated device, each read of IGROUPR0 will cause a VM exit, causing serious performance degradation. This patch replaces the read with the value previously set in `gicv3_cpuif_init`, and we assume that this value has not been modified after initialization. Signed-off-by: ouyangxiangzhen <[email protected]>
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Nov 7, 2024
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Summary
This patch is necessary to optimize the handling of SGI (Software Generated Interrupts) in a virtualized environment on ARM64 architecture. The original implementation required reading the IGROUPR0 register each time an SGI was sent, which, due to the GIC Redistributor being a purely emulated device, caused a VM exit. This VM exit leads to significant performance degradation. The patch addresses this issue by replacing the read operation with a predefined value set during the initialization in
gicv3_cpuif_init, assuming that this value remains unmodified post-initialization.Impact
The change primarily affects the performance of virtualized environments by reducing the number of VM exits caused by SGI handling. Users running virtual machines on ARM64 hardware should experience improved performance, especially in scenarios with frequent SGI usage. There are no direct changes to the build process, hardware requirements, or documentation. Security and compatibility are not directly impacted by this change, but the overall system performance may be enhanced due to reduced VM exits.
Testing
The change was verified on QEMU-virt/arm64.