Hi Robin, On 18/02/2020 18:01, Robin Murphy wrote: > On 18/02/2020 5:43 pm, James Morse wrote: >> On 16/02/2020 18:53, Marc Zyngier wrote: >>> The AArch32 CP14 DBGDIDR has bit 15 set to RES1, which our current >>> emulation doesn't set. Just add the missing bit. >>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c >>> index 3e909b117f0c..da82c4b03aab 100644 >>> --- a/arch/arm64/kvm/sys_regs.c >>> +++ b/arch/arm64/kvm/sys_regs.c >>> @@ -1658,7 +1658,7 @@ static bool trap_dbgidr(struct kvm_vcpu *vcpu, >>> p->regval = ((((dfr >> ID_AA64DFR0_WRPS_SHIFT) & 0xf) << 28) | >>> (((dfr >> ID_AA64DFR0_BRPS_SHIFT) & 0xf) << 24) | >>> (((dfr >> ID_AA64DFR0_CTX_CMPS_SHIFT) & 0xf) << 20) >>> - | (6 << 16) | (el3 << 14) | (el3 << 12)); >>> + | (6 << 16) | (1 << 15) | (el3 << 14) | (el3 << 12)); >> >> Hmmm, where el3 is: >> | u32 el3 = !!cpuid_feature_extract_unsigned_field(pfr, ID_AA64PFR0_EL3_SHIFT); >> >> Aren't we depending on the compilers 'true' being 1 here? > > Pretty much, but thankfully the only compilers we support are C compilers: > > "The result of the logical negation operator ! is 0 if the value of its operand compares > unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int." Excellent. I thought this was the sort of thing that couldn't be depended on! > And now I have you to thank for flashbacks to bitwise logical operators in Visual Basic... :P ... sorry? Thanks, James
