linux-kernel - Re: [PATCH v1 2/3] kvm: svm: Add kvm_fast_pio

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Date:   Mon, 21 Nov 2016 15:50:29 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Brijesh Singh <brijesh.singh@....com>, kvm@...r.kernel.org
Cc:     Thomas.Lendacky@....com, rkrcmar@...hat.com, joro@...tes.org,
        x86@...nel.org, linux-kernel@...r.kernel.org, mingo@...hat.com,
        hpa@...or.com, tglx@...utronix.de, bp@...e.de
Subject: Re: [PATCH v1 2/3] kvm: svm: Add kvm_fast_pio_in support



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

> +	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;
> +	}