Re: [PATCH v2 12/21] KVM:x86: Add fault checks for guest CR4.CET setting

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On 5/5/2023 1:01 PM, Binbin Wu wrote:


On 4/21/2023 9:46 PM, Yang Weijiang wrote:
[...]
@@ -995,6 +995,9 @@ int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)           (is_64_bit_mode(vcpu) || kvm_is_cr4_bit_set(vcpu, X86_CR4_PCIDE)))
          return 1;
  +    if (!(cr0 & X86_CR0_WP) && kvm_read_cr4_bits(vcpu, X86_CR4_CET))
You can use kvm_is_cr4_bit_set() instead of kvm_read_cr4_bits()

Good suggestion, thanks!


+        return 1;
+
      static_call(kvm_x86_set_cr0)(vcpu, cr0);
        kvm_post_set_cr0(vcpu, old_cr0, cr0);
@@ -1210,6 +1213,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
              return 1;
      }
  +    if ((cr4 & X86_CR4_CET) && !(kvm_read_cr0(vcpu) & X86_CR0_WP))
You can use kvm_is_cr0_bit_set() to check X86_CR0_WP

OK.


+        return 1;
+

[...]
@@ -536,6 +536,9 @@ bool kvm_msr_allowed(struct kvm_vcpu *vcpu, u32 index, u32 type);
          __reserved_bits |= X86_CR4_VMXE;        \
      if (!__cpu_has(__c, X86_FEATURE_PCID))          \
          __reserved_bits |= X86_CR4_PCIDE;       \
+    if (!__cpu_has(__c, X86_FEATURE_SHSTK) &&    \
+        !__cpu_has(__c, X86_FEATURE_IBT))        \
+        __reserved_bits |= X86_CR4_CET;        \
IMO, it is a bit wired to split this part from the change of CR4_RESERVED_BITS.

Make sense, will move these lines to other patch.



__reserved_bits;                                \
  })




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