linux-kernel - Re: [PATCH v12 21/23] KVM: selftests: Add wrapper for TDX MMIO from guest

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Message-ID: <6904c5ee707e1_231474100ce@iweiny-mobl.notmuch>
Date: Fri, 31 Oct 2025 09:21:34 -0500
From: Ira Weiny <ira.weiny@...el.com>
To: Sagi Shahar <sagis@...gle.com>, <linux-kselftest@...r.kernel.org>, "Paolo
 Bonzini" <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>, "Sean
 Christopherson" <seanjc@...gle.com>, Ackerley Tng <ackerleytng@...gle.com>,
	Ryan Afranji <afranji@...gle.com>, Andrew Jones <ajones@...tanamicro.com>,
	Isaku Yamahata <isaku.yamahata@...el.com>, Erdem Aktas
	<erdemaktas@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, "Roger
 Wang" <runanwang@...gle.com>, Binbin Wu <binbin.wu@...ux.intel.com>, "Oliver
 Upton" <oliver.upton@...ux.dev>, "Pratik R. Sampat"
	<pratikrajesh.sampat@....com>, Reinette Chatre <reinette.chatre@...el.com>,
	Ira Weiny <ira.weiny@...el.com>, Chao Gao <chao.gao@...el.com>, Chenyi Qiang
	<chenyi.qiang@...el.com>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
Subject: Re: [PATCH v12 21/23] KVM: selftests: Add wrapper for TDX MMIO from
 guest

Sagi Shahar wrote:
> Add utility function to issue MMIO TDCALL from TDX guests.

Some detail from the spec would be nice here.

[snip]

> diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c b/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c
> new file mode 100644
> index 000000000000..f9c1acd5b30c
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c
> @@ -0,0 +1,23 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include "tdx/tdcall.h"
> +#include "tdx/tdx.h"
> +
> +#define TDG_VP_VMCALL 0
> +
> +#define TDG_VP_VMCALL_VE_REQUEST_MMIO	48
> +
> +uint64_t tdg_vp_vmcall_ve_request_mmio_write(uint64_t address, uint64_t size,

Size is limited to specific values.  An enum would help here to self
document/limit issues.

enum mmio_write_size {
	MMIO_SIZE_1B,
	MMIO_SIZE_2B,
	MMIO_SIZE_4B,
	MMIO_SIZE_8B
};

Ira

[snip]