linux-kernel - Re: [PATCH v6 39/44] KVM: VMX: Bug the VM if either MSR auto-load list is full

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Message-ID: <a34caf32-a0e0-4bd1-a670-14ecb3756ae6@linux.intel.com>
Date: Fri, 9 Jan 2026 08:29:50 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oupton@...nel.org>,
 Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>,
 Huacai Chen <chenhuacai@...nel.org>, Anup Patel <anup@...infault.org>,
 Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>,
 Albert Ou <aou@...s.berkeley.edu>, Xin Li <xin@...or.com>,
 "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>,
 linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
 kvm@...r.kernel.org, loongarch@...ts.linux.dev,
 kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Mingwei Zhang <mizhang@...gle.com>, Xudong Hao <xudong.hao@...el.com>,
 Sandipan Das <sandipan.das@....com>,
 Xiong Zhang <xiong.y.zhang@...ux.intel.com>,
 Manali Shukla <manali.shukla@....com>, Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v6 39/44] KVM: VMX: Bug the VM if either MSR auto-load
 list is full

On 1/9/2026 4:04 AM, Sean Christopherson wrote:
> On Mon, Dec 08, 2025, Dapeng Mi wrote:
>> On 12/6/2025 8:17 AM, Sean Christopherson wrote:
>>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>>> index 38491962b2c1..2c50ebf4ff1b 100644
>>> --- a/arch/x86/kvm/vmx/vmx.c
>>> +++ b/arch/x86/kvm/vmx/vmx.c
>>> @@ -1098,6 +1098,7 @@ static void add_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr,
>>>  {
>>>  	int i, j = 0;
>>>  	struct msr_autoload *m = &vmx->msr_autoload;
>>> +	struct kvm *kvm = vmx->vcpu.kvm;
>>>  
>>>  	switch (msr) {
>>>  	case MSR_EFER:
>>> @@ -1134,12 +1135,10 @@ static void add_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr,
>>>  	i = vmx_find_loadstore_msr_slot(&m->guest, msr);
>>>  	j = vmx_find_loadstore_msr_slot(&m->host, msr);
>>>  
>>> -	if ((i < 0 && m->guest.nr == MAX_NR_LOADSTORE_MSRS) ||
>>> -	    (j < 0 &&  m->host.nr == MAX_NR_LOADSTORE_MSRS)) {
>>> -		printk_once(KERN_WARNING "Not enough msr switch entries. "
>>> -				"Can't add msr %x\n", msr);
>>> +	if (KVM_BUG_ON(i < 0 && m->guest.nr == MAX_NR_LOADSTORE_MSRS, kvm) ||
>>> +	    KVM_BUG_ON(j < 0 &&  m->host.nr == MAX_NR_LOADSTORE_MSRS, kvm))
>> nit: Remove one extra space before "m->host.nr".
> Oh, that's intentional, so that the rest of the line is aligned with the "guest"
> line above.

Good to know. Thanks.