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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id l10sm8446000pff.119.2021.10.11.13.23.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Oct 2021 13:23:46 -0700 (PDT) Date: Mon, 11 Oct 2021 20:23:42 +0000 From: Sean Christopherson To: Vipin Sharma Cc: pbonzini@redhat.com, dmatlack@google.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: VMX: Add a wrapper for reading INVPCID/INVEPT/INVVPID type Message-ID: References: <20211011194615.2955791-1-vipinsh@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211011194615.2955791-1-vipinsh@google.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Oct 11, 2021, Vipin Sharma wrote: > Add a common helper function to read invalidation type specified by a > trapped INVPCID/INVEPT/INVVPID instruction. > > Add a symbol constant for max INVPCID type. > > No functional change intended. > > Signed-off-by: Vipin Sharma > --- > arch/x86/include/asm/invpcid.h | 1 + > arch/x86/kvm/vmx/nested.c | 4 ++-- > arch/x86/kvm/vmx/vmx.c | 4 ++-- > arch/x86/kvm/vmx/vmx.h | 12 ++++++++++++ > 4 files changed, 17 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/include/asm/invpcid.h b/arch/x86/include/asm/invpcid.h > index 734482afbf81..b5ac26784c1b 100644 > --- a/arch/x86/include/asm/invpcid.h > +++ b/arch/x86/include/asm/invpcid.h > @@ -21,6 +21,7 @@ static inline void __invpcid(unsigned long pcid, unsigned long addr, > #define INVPCID_TYPE_SINGLE_CTXT 1 > #define INVPCID_TYPE_ALL_INCL_GLOBAL 2 > #define INVPCID_TYPE_ALL_NON_GLOBAL 3 > +#define INVPCID_TYPE_MAX 3 ... > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 1c8b2b6e7ed9..77f72a41dde3 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -5502,9 +5502,9 @@ static int handle_invpcid(struct kvm_vcpu *vcpu) > } > > vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO); > - type = kvm_register_read(vcpu, (vmx_instruction_info >> 28) & 0xf); > + type = vmx_read_invalidation_type(vcpu, vmx_instruction_info); I would prefer to keep the register read visibile in this code so that it's obvious what exactly is being read. With this approach, it's not clear that KVM is reading a GPR vs. VMCS vs. simply extracting "type" from "vmx_instruction_info". And it's not just the INV* instruction, VMREAD and VMWRITE use the same encoding. The hardest part is coming up with a name :-) Maybe do the usually-ill-advised approach of following the SDM verbatim? Reg2 is common to all flavors, so this? gpr_index = vmx_get_instr_info_reg2(vmx_instruction_info); type = kvm_register_read(vcpu, gpr_index); > > - if (type > 3) { > + if (type > INVPCID_TYPE_MAX) { Hrm, I don't love this because it's not auto-updating in the unlikely chance that a new type is added. I definitely don't like open coding '3' either. What about going with a verbose option of if (type != INVPCID_TYPE_INDIV_ADDR && type != INVPCID_TYPE_SINGLE_CTXT && type != INVPCID_TYPE_ALL_INCL_GLOBAL && type != INVPCID_TYPE_ALL_NON_GLOBAL) { kvm_inject_gp(vcpu, 0); return 1; } It's kind of gross, but gcc10 is smart enought to coalesce those all into a single CMP , 3; JA <#GP>, i.e. the resulting binary is identical. > kvm_inject_gp(vcpu, 0); > return 1; > } > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h > index 592217fd7d92..eeafcce57df7 100644 > --- a/arch/x86/kvm/vmx/vmx.h > +++ b/arch/x86/kvm/vmx/vmx.h > @@ -522,4 +522,16 @@ static inline bool vmx_guest_state_valid(struct kvm_vcpu *vcpu) > > void dump_vmcs(struct kvm_vcpu *vcpu); > > +/* > + * When handling a VM-exit for one of INVPCID, INVEPT or INVVPID, read the type > + * of invalidation specified by the instruction. > + */ > +static inline unsigned long vmx_read_invalidation_type(struct kvm_vcpu *vcpu, > + u32 vmx_instr_info) > +{ > + u32 vmx_instr_reg2 = (vmx_instr_info >> 28) & 0xf; > + > + return kvm_register_read(vcpu, vmx_instr_reg2); > +} > + > #endif /* __KVM_X86_VMX_H */ > -- > 2.33.0.882.g93a45727a2-goog >