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SubjectRe: [RFC PATCH v2 07/19] RISC-V: KVM: Implement KVM_GET_ONE_REG/KVM_SET_ONE_REG ioctls
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On 05/08/19 13:37, Christian Borntraeger wrote:
> While have ONE_REG will certainly work, have you considered the sync_reg scheme
> (registers as part of kvm_run structure)
> This will speed up the exit to QEMU as you do not have to do multiple ioctls
> (each imposing a systemcall overhead) for one exit.
>
> Ideally you should not exit too often into qemu, but for those cases sync_regs
> is faster than ONE_REG.

At least in theory, RISC-V should never have exits to QEMU that need
accessing the registers. (The same is true for x86; Google implemented
sync_regs because they moved the instruction emulator to userspace in
their fork).

Paolo

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