On Tue, 2023-02-14 at 09:27 +0800, Binbin Wu wrote: > This patch removes CR4.LAM_SUP from cr4_reserved_bits to allows the > setting of X86_CR4_LAM_SUP by guest Yes > if the hardware platform supports > the feature. More precisely, if guest_cpuid_has() LAM feature. QEMU could turn feature off even if underlying host/KVM tells supporting it. > > The interception of CR4 is decided by CR4 guest/host mask and CR4 > read > shadow. > My interpretation is that "intercept CR4.x bit" is the opposite of "guest own CR4.x bit". Both of them are implemented via CR4 guest/host mask and CR4 shadow, whose combination decides corresponding CR4.x bit access causes VM exit or not. When we changes some bits in CR4_RESERVED_BITS and __cr4_reserved_bits(), we changes vcpu->arch.cr4_guest_owned_bits which eventually forms the effective vmcs_writel(CR4_GUEST_HOST_MASK).
