linux-kernel - Re: [PATCH 6/7] KVM: TDX: Handle TDX PV port I/O hypercall

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Message-ID: <Z1gNIRWSMy2w7CYp@intel.com>
Date: Tue, 10 Dec 2024 17:42:57 +0800
From: Chao Gao <chao.gao@...el.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
CC: <pbonzini@...hat.com>, <seanjc@...gle.com>, <kvm@...r.kernel.org>,
	<rick.p.edgecombe@...el.com>, <kai.huang@...el.com>,
	<adrian.hunter@...el.com>, <reinette.chatre@...el.com>,
	<xiaoyao.li@...el.com>, <tony.lindgren@...ux.intel.com>,
	<isaku.yamahata@...el.com>, <yan.y.zhao@...el.com>, <michael.roth@....com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/7] KVM: TDX: Handle TDX PV port I/O hypercall

>+static int tdx_emulate_io(struct kvm_vcpu *vcpu)
>+{
>+	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
>+	unsigned long val = 0;
>+	unsigned int port;
>+	int size, ret;
>+	bool write;

..

>+
>+	++vcpu->stat.io_exits;
>+
>+	size = tdvmcall_a0_read(vcpu);
>+	write = tdvmcall_a1_read(vcpu);

a1 (i.e., R13) should be either 0 or 1. Other values are reserved according to
the GHCI spec. It is not appropriate to cast it to a boolean. For example, if
R13=2, KVM shouldn't treat it as a write request; instead, this request should
be rejected.

>+	port = tdvmcall_a2_read(vcpu);
>+
>+	if (size != 1 && size != 2 && size != 4) {
>+		tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_INVALID_OPERAND);
>+		return 1;
>+	}