On 03/28/2011 03:56 PM, Roedel, Joerg wrote:
On Mon, Mar 28, 2011 at 08:35:54AM -0400, Avi Kivity wrote: > On 03/28/2011 12:46 PM, Joerg Roedel wrote: > > This patch add intercept checks into the KVM instruction > > emulator to check for the 8 instructions that access the > > descriptor table addresses. > > > > +static struct opcode group6[] = { > > + DI(ModRM, sldt), > > + DI(ModRM, str), > > + DI(ModRM | Priv, lldt), > > + DI(ModRM | Priv, ltr), > > + N, N, N, N, > > +}; > > + > > static struct group_dual group7 = { { > > - N, N, DI(ModRM | SrcMem | Priv, lgdt), DI(ModRM | SrcMem | Priv, lidt), > > + DI(ModRM | DstMem | Priv, sgdt), DI(ModRM | DstMem | Priv, sidt), > > + DI(ModRM | SrcMem | Priv, lgdt), DI(ModRM | SrcMem | Priv, lidt), > > | Mov, to avoid RMW for SIDT, for example. Also need to indicate the > operand size correctly. > > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > > index 381b038..485a09f 100644 > > --- a/arch/x86/kvm/svm.c > > +++ b/arch/x86/kvm/svm.c > > @@ -3871,6 +3871,10 @@ static void svm_fpu_deactivate(struct kvm_vcpu *vcpu) > > #define POST_EX(exit) { .exit_code = (exit), \ > > .stage = X86_ICPT_POST_EXCEPT, \ > > .valid = true } > > +#define POST_MEM(exit) { .exit_code = (exit), \ > > + .stage = X86_ICPT_POST_MEMACCESS, \ > > + .valid = true } > > + > > > > static struct __x86_intercept { > > u32 exit_code; > > @@ -3884,9 +3888,18 @@ static struct __x86_intercept { > > [x86_intercept_smsw] = POST_EX(SVM_EXIT_READ_CR0), > > [x86_intercept_dr_read] = POST_EX(SVM_EXIT_READ_DR0), > > [x86_intercept_dr_write] = POST_EX(SVM_EXIT_WRITE_DR0), > > + [x86_intercept_sldt] = POST_MEM(SVM_EXIT_LDTR_READ), > > + [x86_intercept_str] = POST_MEM(SVM_EXIT_TR_READ), > > + [x86_intercept_lldt] = POST_MEM(SVM_EXIT_LDTR_WRITE), > > + [x86_intercept_ltr] = POST_MEM(SVM_EXIT_TR_WRITE), > > + [x86_intercept_sgdt] = POST_MEM(SVM_EXIT_GDTR_READ), > > + [x86_intercept_sidt] = POST_MEM(SVM_EXIT_IDTR_READ), > > + [x86_intercept_lgdt] = POST_MEM(SVM_EXIT_GDTR_WRITE), > > + [x86_intercept_lidt] = POST_MEM(SVM_EXIT_IDTR_WRITE), > > }; > > Spec says POST_EX()?Well, not entirely clear. Spec says that #GP takes precedence before the intercept and the intruction reference says the #GP fires if the supplied address is not within segment limits or the segment itself is not valid, which, in my interpretation, made them POST_MEM.
My interpretation would be that a #GP(0) due to CPL check takes precedence over the intercept, which takes precedence over a #GP(selector) due to the actual memory reference.
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