On Fri, Jul 08, 2022 at 02:23:43PM +1200, Kai Huang <kai.huang@xxxxxxxxx> wrote: > On Mon, 2022-06-27 at 14:53 -0700, isaku.yamahata@xxxxxxxxx wrote: > > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > > > To support TDX, KVM is enhanced to operate with #VE. For TDX, KVM programs > > to inject #VE conditionally and set #VE suppress bit in EPT entry. For VMX > > case, #VE isn't used. If #VE happens for VMX, it's a bug. To be > > defensive (test that VMX case isn't broken), introduce option > > ept_violation_ve_test and when it's set, set error. > > I don't see why we need this patch. It may be helpful during your test, but why > do we need this patch for formal submission? > > And for a normal guest, what prevents one vcpu from sending #VE IPI to another > vcpu? Paolo suggested it as follows. Maybe it should be kernel config. (I forgot to add suggested-by. I'll add it) https://lore.kernel.org/lkml/84d56339-4a8a-6ddb-17cb-12074588ba9c@xxxxxxxxxx/ > On 3/4/22 20:48, isaku.yamahata@xxxxxxxxx wrote: > > + if (enable_ept) { > > + const u64 init_value = enable_tdx ? VMX_EPT_SUPPRESS_VE_BIT : 0ull; > > kvm_mmu_set_ept_masks(enable_ept_ad_bits, > > - cpu_has_vmx_ept_execute_only()); > > + cpu_has_vmx_ept_execute_only(), init_value); > > + kvm_mmu_set_spte_init_value(init_value); > > + } > > I think kvm-intel.ko should use VMX_EPT_SUPPRESS_VE_BIT unconditionally > as the init value. The bit is ignored anyway if the "EPT-violation #VE" > execution control is 0. Otherwise looks good, but I have a couple more > crazy ideas: > > 1) there could even be a test mode where KVM enables the execution > control, traps #VE in the exception bitmap, and shouts loudly if it gets > a #VE. That might avoid hard-to-find bugs due to forgetting about > VMX_EPT_SUPPRESS_VE_BIT. > > 2) or even, perhaps the init_value for the TDP MMU could set bit 63 > _unconditionally_, because KVM always sets the NX bit on AMD hardware. > That would remove the whole infrastructure to keep shadow_init_value, > because it would be constant 0 in mmu.c and constant BIT(63) in tdp_mmu.c. > > Sean, what do you think? > > Paolo -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
