On Thu, Oct 19, 2023, Xin Li wrote: > On 10/18/2023 2:08 PM, Sean Christopherson wrote: > > > > Add IA32_VMX_BASIC MSR bitfield shift macros and use them to define VMX > > > basic information bitfields. > > > > Why? Unless something actually uses the shift independently, just define the > > BIT_ULL(...) straightaway. > > Well, reading "BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |" is hard. I wasn't suggesting that, I was suggesting: #define VMX_BASIC_INOUT BIT_ULL(54) instead of #define VMX_BASIC_INOUT BIT_ULL(VMX_BASIC_INOUT_SHIFT) Defining a shift adds a pointless layer of indirection (if the shift isn't used directly). It's especially problematic when there are a series of definitions. E.g. if I want to know which bit a flag corresponds to, this: #define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(48) #define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(49) #define VMX_BASIC_MEM_TYPE(x) (((x) & GENMASK_ULL(53, 50)) >> 50) #define VMX_BASIC_INOUT BIT_ULL(54) #define VMX_BASIC_TRUE_CTLS BIT_ULL(55) is much easier for me to process than this #define VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT 48 #define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT) #define VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT 49 #define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT) #define VMX_BASIC_MEM_TYPE_SHIFT 50 #define VMX_BASIC_INOUT_SHIFT 54 #define VMX_BASIC_INOUT BIT_ULL(VMX_BASIC_INOUT_SHIFT) #define VMX_BASIC_TRUE_CTLS_SHIFT 55 #define VMX_BASIC_TRUE_CTLS BIT_ULL(VMX_BASIC_TRUE_CTLS_SHIFT) and the former also tends to work better for IDEs that support peeking at macro definitions. > > > --- > > > arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------ > > > arch/x86/kvm/vmx/nested.c | 10 +++------ > > > arch/x86/kvm/vmx/vmx.c | 2 +- > > > tools/arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------ > > > > Please drop the tools/ update, copying kernel headers into tools is a perf tools > > thing that I want no part of. > > > > https://lore.kernel.org/all/Y8bZ%2FJ98V5i3wG%2Fv@xxxxxxxxxx > > why can't we simply remove tools/arch/x86/include/asm/msr-index.h? That's a question for the tools/perf folks, though I believe the answer is partly that the perf tooling relies on *exactly* matching kernel-internal structures, and so tools/perf doesn't want to rely on installed headers. > > > +#define VMX_BASIC_RESERVED_BITS \ > > > + (VMX_BASIC_ALWAYS_0 | \ > > > + VMX_BASIC_RESERVED_RANGE_1 | \ > > > + VMX_BASIC_RESERVED_RANGE_2) > > > > I don't see any value in defining VMX_BASIC_RESERVED_RANGE_1 and > > VMX_BASIC_RESERVED_RANGE_2 separately. Or VMX_BASIC_ALWAYS_0 for the matter. > > And I don't think these macros need to go in msr-index.h, e.g. just define them > > above vmx_restore_vmx_basic() as that's likely going to be the only user, ever. > > hmm, I'm overusing macros, better do: > #define VMX_BASIC_RESERVED_BITS \ > (BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56)) Please define from high=>low, x86 is little-endian. I.e. (GENMASK_ULL(63, 56) | GENMASK_ULL(47, 45) | BIT_ULL(31)) > Probably should also move VMX MSR field defs from msr-index.h to > a vmx header file. Why bother putting them in a header? As above, it's extremely unlikely anything besides vmx_restore_vmx_basic() will ever care about exactly which bits are reserved.
