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([2001:b07:6468:f312:b55d:5ed2:8a41:41ea]) by smtp.gmail.com with ESMTPSA id a13sm19618574wrt.64.2020.03.31.07.51.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 31 Mar 2020 07:51:54 -0700 (PDT) Subject: Re: [PATCH] KVM: x86: Fix BUILD_BUG() in __cpuid_entry_get_reg() w/ CONFIG_UBSAN=y To: Sean Christopherson Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Randy Dunlap References: <20200325191259.23559-1-sean.j.christopherson@intel.com> From: Paolo Bonzini Message-ID: Date: Tue, 31 Mar 2020 16:51:53 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200325191259.23559-1-sean.j.christopherson@intel.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/03/20 20:12, Sean Christopherson wrote: > Take the target reg in __cpuid_entry_get_reg() instead of a pointer to a > struct cpuid_reg. When building with -fsanitize=alignment (enabled by > CONFIG_UBSAN=y), some versions of gcc get tripped up on the pointer and > trigger the BUILD_BUG(). > > Reported-by: Randy Dunlap > Fixes: d8577a4c238f8 ("KVM: x86: Do host CPUID at load time to mask KVM cpu caps") > Fixes: 4c61534aaae2a ("KVM: x86: Introduce cpuid_entry_{get,has}() accessors") > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/cpuid.c | 2 +- > arch/x86/kvm/cpuid.h | 8 ++++---- > 2 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 08280d8a2ac9..16d3ae432420 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -269,7 +269,7 @@ static __always_inline void kvm_cpu_cap_mask(enum cpuid_leafs leaf, u32 mask) > cpuid_count(cpuid.function, cpuid.index, > &entry.eax, &entry.ebx, &entry.ecx, &entry.edx); > > - kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, &cpuid); > + kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, cpuid.reg); > } > > void kvm_set_cpu_caps(void) > diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h > index 23b4cd1ad986..63a70f6a3df3 100644 > --- a/arch/x86/kvm/cpuid.h > +++ b/arch/x86/kvm/cpuid.h > @@ -99,9 +99,9 @@ static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_featu > } > > static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry, > - const struct cpuid_reg *cpuid) > + u32 reg) > { > - switch (cpuid->reg) { > + switch (reg) { > case CPUID_EAX: > return &entry->eax; > case CPUID_EBX: > @@ -121,7 +121,7 @@ static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry, > { > const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature); > > - return __cpuid_entry_get_reg(entry, &cpuid); > + return __cpuid_entry_get_reg(entry, cpuid.reg); > } > > static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry, > @@ -189,7 +189,7 @@ static __always_inline u32 *guest_cpuid_get_register(struct kvm_vcpu *vcpu, > if (!entry) > return NULL; > > - return __cpuid_entry_get_reg(entry, &cpuid); > + return __cpuid_entry_get_reg(entry, cpuid.reg); > } > > static __always_inline bool guest_cpuid_has(struct kvm_vcpu *vcpu, > Queued, thanks. Paolo