Re: [PATCH V2] KVM/x86: Check input paging mode when cs.l is set

[Lan, Tianyu]

On 12/14/2017 7:41 PM, Paolo Bonzini wrote:

On 14/12/2017 04:55, Lan Tianyu wrote:

+        * When EFER.LME and CR0.PG are set, CR4.PAE and EFER.LMA
+        * must be set.
+        */
+       if ((sregs->efer & EFER_LME) && (sregs->cr0 & X86_CR0_PG_BIT)) {
+               if (!(sregs->cr4 & X86_CR4_PAE_BIT))
+                       return -EINVAL;
+               if (!(sregs->efer & EFER_LMA))
+                       return -EINVAL;
+       } else if (sregs->efer & EFER_LMA)

This can just be "(sregs->efer & EFER_LMA) || sregs->cs.l", making the
next "if" redundant.  Even better written as

        if ((sregs->efer & EFER_LME) && (sregs->cr0 & X86_CR0_PG_BIT)) {
                /*
                 * When EFER.LME and CR0.PG are set, the processor is in
                 * 64-bit mode (though maybe in a 32-bit code segment).
                 * CR4.PAE and EFER.LMA must be set.
                 */
                if (... || ...)
                        return -EINVAL;
        } else {
                /*
                 * Not in 64-bit mode: EFER.LMA is clear and the code
                 * segment cannot be 64-bit.
                 */
                if (... || ...)
                        return -EINVAL;
        }

Paolo

OK. Thanks for your guide. just send v3. Please have a look.