linux-kernel - Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted

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Date:   Thu, 23 Feb 2023 13:24:45 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        Sean Christopherson <seanjc@...gle.com>
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Subject: Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range
 to map as encrypted

On 2/23/23 13:15, Michael Kelley (LINUX) wrote:
> Or statically set a default stub function for is_private_mmio() that returns "false".
> Then there's no need to check for NULL, and only platforms that want to use it
> have to code anything.  Several other entries in x86_platform have such defaults.

Yeah, that's what I was thinking too, like 'x86_op_int_noop':

> struct x86_platform_ops x86_platform __ro_after_init = {
>         .calibrate_cpu                  = native_calibrate_cpu_early,
>         .calibrate_tsc                  = native_calibrate_tsc,
...
>         .hyper.pin_vcpu                 = x86_op_int_noop,

It's kinda silly to do an indirect call to a two-instruction function,
but this is a pretty slow path.