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Date:   Wed, 23 Nov 2022 08:04:44 -0800
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Subject: Re: [PATCH 1/6] x86/tdx: Support hypercalls for TDX guests on Hyper-V
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To:     Dexuan Cui <decui@microsoft.com>,
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From:   Dave Hansen <dave.hansen@intel.com>
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On 11/22/22 17:56, Dexuan Cui wrote:
>> From: Dexuan Cui
>> [...]
>> The existing asm code for __tdx_hypercall() passes through R10~R15
>> (see TDVMCALL_EXPOSE_REGS_MASK) to the (KVM) hypervisor.
>>
>> Unluckily, for Hyper-V, we need to pass through RDX, R8, R10 and R11
>> to Hyper-V, so I don't think I can use the existing __tdx_hypercall() ?
> I'm checking with the Hyper-V team to see if it's possible for them
> to not use RDX and R8, and use R12 and R13 instead. Will keep the
> thread updated.

That would be nice.  But, to be honest, I don't expect them to change
the ABI for one OS.  It's not a big deal to just make the function a bit
more flexible.