On Fri, Aug 23, 2024 at 6:59 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > Heh, and for MPX, the SDM kinda sorta confirms that LA57 is ignored, though I > doubt the author of this section intended their words to be taken this way :-) > > WRMSR to BNDCFGS will #GP if any of the reserved bits of BNDCFGS is not zero or > if the base address of the bound directory is not canonical. XRSTOR of BNDCFGU > ignores the reserved bits and does not fault if any is non-zero; similarly, it > ignores the upper bits of the base address of the bound directory and sign-extends > the highest implemented bit of the linear address to guarantee the canonicality > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > of this address. I don't believe there was ever a CPU that supported both MPX and LA57. :) Late to the party, as usual, but my interest was piqued by the failure of KVM_SET_NESTED_STATE prior to v6.13 if L1 had CR4.LA57 set, L2 did not, and the VMCS12.HOST_GSBASE had a kernel address > 48 bits wide. The canonicalization checks for the *host* state in the VMCS were done using the guest's CR4.LA57. Shouldn't this series have been cc'd to stable?
