Avi, I also tested the qemu change is not affecting vm86 (no unrestricted guest) code path. Thanks & Regards, Nitin On Wed, 2009-06-03 at 11:08 -0700, Nitin A Kamble wrote: > Hi Avi, > I find that the qemu processor reset state is not per the IA32 > processor specifications. (Sections 8.1.1 of > http://www.intel.com/Assets/PDF/manual/253668.pdf) > > In qemu-kvm.git in file target-i386/helper.c in function cpu_reset the > segment registers are initialized as follows: > > cpu_x86_load_seg_cache(env, R_CS, 0xf000, 0xffff0000, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_CS_MASK | > DESC_R_MASK); > cpu_x86_load_seg_cache(env, R_DS, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK); > cpu_x86_load_seg_cache(env, R_ES, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK); > cpu_x86_load_seg_cache(env, R_SS, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK); > cpu_x86_load_seg_cache(env, R_FS, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK); > cpu_x86_load_seg_cache(env, R_GS, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK); > > While the IA32 cpu reset state specification says that Segment Accessed > bit is also 1 at the time of cpu reset. so the above code should look > like this: > > cpu_x86_load_seg_cache(env, R_CS, 0xf000, 0xffff0000, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_CS_MASK | > DESC_R_MASK | DESC_A_MASK); > cpu_x86_load_seg_cache(env, R_DS, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK | DESC_A_MASK); > cpu_x86_load_seg_cache(env, R_ES, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK| DESC_A_MASK); > cpu_x86_load_seg_cache(env, R_SS, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK |DESC_A_MASK); > cpu_x86_load_seg_cache(env, R_FS, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK); > cpu_x86_load_seg_cache(env, R_GS, 0, 0, 0xffff, > DESC_P_MASK | DESC_S_MASK | DESC_W_MASK); > > This discrepancy is adding the need of the following function in the > unrestricted guest patch. > > +static inline u32 get_segment_ar(int seg) > +{ > + if (!enable_unrestricted_guest) > + return 0xf3; > + > + switch (seg) { > + case VCPU_SREG_CS: > + return 0x9b; > + case VCPU_SREG_TR: > + return 0x8b; > + case VCPU_SREG_LDTR: > + return 0x82; > + default: > + return 0x93; > + } > +} > + > > For the unrestricted guest support either we can fix this discrepancy in > the qemu code, or have a functionality like get_segment_ar() in the kvm > vmx code. > what do you suggest ? > > Thanks & Regards, > Nitin > > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
