On Thu, Apr 25, 2024, Kai Huang wrote: > On Wed, 2024-04-24 at 13:06 -0700, Sean Christopherson wrote: > > > > static inline u32 vmx_basic_vmcs_mem_type(u64 vmx_basic) > > > > { > > > > return (vmx_basic & GENMASK_ULL(53, 50)) >> > > > > VMX_BASIC_MEM_TYPE_SHIFT; > > > > } > > > > > > > > looks not intuitive than original patch. > > > > > > Yeah, agreed, that's taking the worst of both worlds. I'll update patch 5 to drop > > > VMX_BASIC_MEM_TYPE_SHIFT when effectively "moving" it into vmx_basic_vmcs_mem_type(). > > > > Drat. Finally getting back to this, dropping VMX_BASIC_MEM_TYPE_SHIFT doesn't > > work because it's used by nested_vmx_setup_basic(), as is VMX_BASIC_VMCS_SIZE_SHIFT, > > which is presumably why past me kept them around. > > > > I'm leaning towards keeping things as proposed in this series. I don't see us > > gaining a third copy, or even a third user, i.e. I don't think we are creating a > > future problem by open coding the shift in vmx_basic_vmcs_mem_type(). And IMO > > code like this > > > > return (vmx_basic & VMX_BASIC_MEM_TYPE_MASK) >> > > VMX_BASIC_MEM_TYPE_SHIFT; > > > > is an unnecessary obfuscation when there is literally one user (the accessor). > > > > Another idea would be to delete VMX_BASIC_MEM_TYPE_SHIFT and VMX_BASIC_VMCS_SIZE_SHIFT, > > and either open code the values or use local const variables, but that also seems > > like a net negative, e.g. splits the effective definitions over too many locations. > > Alternatively, we can add macros like below to <asm/vmx.h> close to > vmx_basic_vmcs_size() etc, so it's straightforward to see. > > +#define VMX_BSAIC_VMCS12_SIZE ((u64)VMCS12_SIZE << 32) > +#define VMX_BASIC_MEM_TYPE_WB (MEM_TYPE_WB << 50) Hmm, it's a bit hard to see it's specifically VMCS12 size, and given that prior to this series, VMX_BASIC_MEM_TYPE_WB = 6, I'm hesitant to re-introduce/redefine that macro with a different value. What if we add a helper in vmx.h to encode the VMCS info? Then the #defines for the shifts can go away because the open coded shifts are colocated and more obviously related. E.g. static inline u64 vmx_basic_encode_vmcs_info(u32 revision, u16 size, u8 memtype) { return revision | ((u64)size << 32) | ((u64)memtype << 50); } and static void nested_vmx_setup_basic(struct nested_vmx_msrs *msrs) { /* * This MSR reports some information about VMX support. We * should return information about the VMX we emulate for the * guest, and the VMCS structure we give it - not about the * VMX support of the underlying hardware. */ msrs->basic = vmx_basic_encode_vmcs_info(VMCS12_REVISION, VMCS12_SIZE, X86_MEMTYPE_WB); msrs->basic |= VMX_BASIC_TRUE_CTLS if (cpu_has_vmx_basic_inout()) msrs->basic |= VMX_BASIC_INOUT; }