Messages in this thread | | | Date | Tue, 6 Jun 2023 11:08:57 +0800 | Subject | Re: [PATCH v1 3/6] KVM: VMX: Add new ops in kvm_x86_ops for LASS violation check | From | Zeng Guang <> |
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On 6/5/2023 10:07 PM, Yuan Yao wrote: > On Thu, Jun 01, 2023 at 10:23:06PM +0800, Zeng Guang wrote: >> Intel introduces LASS (Linear Address Separation) feature providing >> an independent mechanism to achieve the mode-based protection. >> >> LASS partitions 64-bit linear address space into two halves, user-mode >> address (LA[bit 63]=0) and supervisor-mode address (LA[bit 63]=1). It >> stops any code execution or conditional data access[1] >> 1. from user mode to supervisor-mode address space >> 2. from supervisor mode to user-mode address space >> and generates LASS violation fault accordingly. >> >> +/* >> + * Determine whether an access to the linear address causes a LASS violation. >> + * LASS protection is only effective in long mode. As a prerequisite, caller >> + * should make sure vCPU running in long mode and invoke this api to do LASS >> + * violation check. >> + */ >> +bool vmx_check_lass(struct kvm_vcpu *vcpu, u64 access, u64 la, u32 flags) >> +{ >> + bool user_mode, user_as, rflags_ac; >> + >> + if (!!(flags & X86EMUL_F_SKIPLASS) || >> + !kvm_is_cr4_bit_set(vcpu, X86_CR4_LASS)) >> + return false; >> + >> + WARN_ON_ONCE(!is_long_mode(vcpu)); >> + >> + user_as = !(la >> 63); >> + >> + /* >> + * An access is a supervisor-mode access if CPL < 3 or if it implicitly >> + * accesses a system data structure. For implicit accesses to system >> + * data structure, the processor acts as if RFLAGS.AC is clear. >> + */ >> + if (access & PFERR_IMPLICIT_ACCESS) { >> + user_mode = false; >> + rflags_ac = false; >> + } else { >> + user_mode = vmx_get_cpl(vcpu) == 3; >> + if (!user_mode) >> + rflags_ac = !!(kvm_get_rflags(vcpu) & X86_EFLAGS_AC); >> + } >> + >> + if (user_mode == user_as) > Confused by user_as, it's role of address(U/S) so how about > "user_addr" ? "if (user_mode == user_addr)" looks more clear > to me. > Actually "as" stands for "address space". I suppose it more precise. :)
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