----- Original Message ----- > From: "Tom Lendacky" <thomas.lendacky@xxxxxxx> > To: "Paolo Bonzini" <pbonzini@xxxxxxxxxx>, "Brijesh Singh" <brijesh.singh@xxxxxxx>, kvm@xxxxxxxxxxxxxxx > Cc: rkrcmar@xxxxxxxxxx, joro@xxxxxxxxxx, x86@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, mingo@xxxxxxxxxx, > hpa@xxxxxxxxx, tglx@xxxxxxxxxxxxx, bp@xxxxxxx > Sent: Tuesday, November 22, 2016 3:25:52 PM > Subject: Re: [PATCH v1 2/3] kvm: svm: Add kvm_fast_pio_in support > > On 11/21/2016 8:50 AM, Paolo Bonzini wrote: > > > > > > On 14/11/2016 23:15, Brijesh Singh wrote: > >> + /* For size less than 4 we merge, else we zero extend */ > >> + val = (size < 4) ? kvm_register_read(vcpu, VCPU_REGS_RAX) : 0; > > > > Are you sure it shouldn't always zero extend the high 32-bits? So "val" > > should be declared as u32. > > > > Paolo > > It should only zero extend when dealing with a 32-bit operation. Any use > of 8 or 16 bit registers leaves the upper 56 or 48 bits as is (see > section 3.1.2.3 in http://support.amd.com/TechDocs/24592.pdf). Duh, right, see also assign_register in arch/x86/kvm/emulate.c. Paolo > Thanks, > Tom > > > > >> + ret = emulator_pio_in_emulated(&vcpu->arch.emulate_ctxt, size, port, > >> + &val, 1); > >> + if (ret) { > >> + kvm_register_write(vcpu, VCPU_REGS_RAX, val); > >> + return ret; > >> + } > -- 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
