KVM: nVMX: Add a helper to encode VMCS info in MSR_IA32_VMX_BASIC

Add a helper to encode the VMCS revision, size, and supported memory types
in MSR_IA32_VMX_BASIC, i.e. when synthesizing KVM's supported BASIC MSR
value, and delete the now unused VMCS size and memtype shift macros.

For a variety of reasons, KVM has shifted (pun intended) to using helpers
to *get* information from the VMX MSRs, as opposed to defined MASK and
SHIFT macros for direct use.  Provide a similar helper for the nested VMX
code, which needs to *set* information, so that KVM isn't left with a mix
of SHIFT macros and dedicated helpers.
Reported-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240605231918.2915961-8-seanjc@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/include/asm/vmx.h

@@ -135,10 +135,8 @@
 #define VMX_VMFUNC_EPTP_SWITCHING               VMFUNC_CONTROL_BIT(EPTP_SWITCHING)
 #define VMFUNC_EPTP_ENTRIES  512
 
-#define VMX_BASIC_VMCS_SIZE_SHIFT		32
 #define VMX_BASIC_32BIT_PHYS_ADDR_ONLY		BIT_ULL(48)
 #define VMX_BASIC_DUAL_MONITOR_TREATMENT	BIT_ULL(49)
-#define VMX_BASIC_MEM_TYPE_SHIFT		50
 #define VMX_BASIC_INOUT				BIT_ULL(54)
 #define VMX_BASIC_TRUE_CTLS			BIT_ULL(55)
 
@@ -157,6 +155,11 @@ static inline u32 vmx_basic_vmcs_mem_type(u64 vmx_basic)
 	return (vmx_basic & GENMASK_ULL(53, 50)) >> 50;
 }
 
+static inline u64 vmx_basic_encode_vmcs_info(u32 revision, u16 size, u8 memtype)
+{
+	return revision | ((u64)size << 32) | ((u64)memtype << 50);
+}
+
 static inline int vmx_misc_preemption_timer_rate(u64 vmx_misc)
 {
 	return vmx_misc & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;

arch/x86/kvm/vmx/nested.c

@@ -7077,12 +7077,10 @@ static void nested_vmx_setup_basic(struct nested_vmx_msrs *msrs)
 	 * guest, and the VMCS structure we give it - not about the
 	 * VMX support of the underlying hardware.
 	 */
-	msrs->basic =
-		VMCS12_REVISION |
-		VMX_BASIC_TRUE_CTLS |
-		((u64)VMCS12_SIZE << VMX_BASIC_VMCS_SIZE_SHIFT) |
-		(X86_MEMTYPE_WB << VMX_BASIC_MEM_TYPE_SHIFT);
+	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;
 }