linux-kernel - Re: [PATCH v16 49/51] KVM: selftests: Add coverate for KVM-defined registers in MSRs test

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Message-ID: <aNI+07tytIMh/YvW@intel.com>
Date: Tue, 23 Sep 2025 14:31:47 +0800
From: Chao Gao <chao.gao@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
CC: Paolo Bonzini <pbonzini@...hat.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Tom Lendacky <thomas.lendacky@....com>,
	Mathias Krause <minipli@...ecurity.net>, John Allen <john.allen@....com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>, Binbin Wu
	<binbin.wu@...ux.intel.com>, Xiaoyao Li <xiaoyao.li@...el.com>, "Maxim
 Levitsky" <mlevitsk@...hat.com>, Zhang Yi Z <yi.z.zhang@...ux.intel.com>,
	"Xin Li" <xin@...or.com>
Subject: Re: [PATCH v16 49/51] KVM: selftests: Add coverate for KVM-defined
 registers in MSRs test

On Fri, Sep 19, 2025 at 03:32:56PM -0700, Sean Christopherson wrote:
>Add test coverage for the KVM-defined GUEST_SSP "register" in the MSRs
>test.  While _KVM's_ goal is to not tie the uAPI of KVM-defined registers
>to any particular internal implementation, i.e. to not commit in uAPI to
>handling GUEST_SSP as an MSR, treating GUEST_SSP as an MSR for testing
>purposes is a-ok and is a naturally fit given the semantics of SSP.
>
>Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Chao Gao <chao.gao@...el.com>

<snip>

>+static bool vcpu_has_reg(struct kvm_vcpu *vcpu, u64 reg)
>+{
>+	struct {
>+		struct kvm_reg_list list;
>+		u64 regs[KVM_X86_MAX_NR_REGS];
>+	} regs = {};
>+	int r, i;
>+
>+	/*
>+	 * If KVM_GET_REG_LIST succeeds with n=0, i.e. there are no supported
>+	 * regs, then the vCPU obviously doesn't support the reg.
>+	 */
>+	r = __vcpu_ioctl(vcpu, KVM_GET_REG_LIST, &regs.list.n);
						 ^^^^^^^^^^^^
it would be more clear to use &reg.list here.

>+	if (!r)
>+		return false;
>+
>+	TEST_ASSERT_EQ(errno, E2BIG);
>+
>+	/*
>+	 * KVM x86 is expected to support enumerating a relative small number
>+	 * of regs.  The majority of registers supported by KVM_{G,S}ET_ONE_REG
>+	 * are enumerated via other ioctls, e.g. KVM_GET_MSR_INDEX_LIST.  For
>+	 * simplicity, hardcode the maximum number of regs and manually update
>+	 * the test as necessary.
>+	 */
>+	TEST_ASSERT(regs.list.n <= KVM_X86_MAX_NR_REGS,
>+		    "KVM reports %llu regs, test expects at most %u regs, stale test?",
>+		    regs.list.n, KVM_X86_MAX_NR_REGS);
>+
>+	vcpu_ioctl(vcpu, KVM_GET_REG_LIST, &regs.list.n);

Ditto.