[PATCH v8 06/10] KVM: nVMX: Use macros and #defines in vmx_restore_vmx_basic()

Sean Christopherson
2024-06-05T23:19:33Z

From: Xin Li <xin3.li@intel.com>

Use macros in vmx_restore_vmx_basic() instead of open coding everything
using BIT_ULL() and GENMASK_ULL(). Opportunistically split feature bits
and reserved bits into separate variables, and add a comment explaining
the subset logic (it's not immediately obvious that the set of feature
bits is NOT the set of _supported_ feature bits).

Cc: Shan Kang <shan.kang@intel.com>
Cc: Kai Huang <kai.huang@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
[sean: split to separate patch, write changelog, drop #defines]
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/nested.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 3bd6c026f192..6402def985af 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1250,21 +1250,32 @@ static bool is_bitwise_subset(u64 superset, u64 subset, u64 mask)

static int vmx_restore_vmx_basic(struct vcpu_vmx *vmx, u64 data)
{
- const u64 feature_and_reserved =
- /* feature (except bit 48; see below) */
- BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |
- /* reserved */
- BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56);
+ const u64 feature_bits = VMX_BASIC_DUAL_MONITOR_TREATMENT |
+ VMX_BASIC_INOUT |
+ VMX_BASIC_TRUE_CTLS;
+
+ const u64 reserved_bits = GENMASK_ULL(63, 56) |
+ GENMASK_ULL(47, 45) |
+ BIT_ULL(31);
+
u64 vmx_basic = vmcs_config.nested.basic;

- if (!is_bitwise_subset(vmx_basic, data, feature_and_reserved))
+ BUILD_BUG_ON(feature_bits & reserved_bits);
+
+ /*
+ * Except for 32BIT_PHYS_ADDR_ONLY, which is an anti-feature bit (has
+ * inverted polarity), the incoming value must not set feature bits or
+ * reserved bits that aren't allowed/supported by KVM. Fields, i.e.
+ * multi-bit values, are explicitly checked below.
+ */
+ if (!is_bitwise_subset(vmx_basic, data, feature_bits | reserved_bits))
return -EINVAL;

/*
* KVM does not emulate a version of VMX that constrains physical
* addresses of VMX structures (e.g. VMCS) to 32-bits.
*/
- if (data & BIT_ULL(48))
+ if (data & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
return -EINVAL;

if (vmx_basic_vmcs_revision_id(vmx_basic) !=
--
2.45.1.467.gbab1589fc0-goog