linux-kernel - Re: [PATCH v17 1/7] arm/arm64: Probe for the presence of KVM hypervisor

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Message-ID: <29f8b6f5faf33472b74ab5f2406c6081@kernel.org>
Date:   Fri, 05 Feb 2021 11:23:37 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Will Deacon <will@...nel.org>, Steven Price <steven.price@....com>
Cc:     netdev@...r.kernel.org, yangbo.lu@....com, john.stultz@...aro.org,
        tglx@...utronix.de, pbonzini@...hat.com, seanjc@...gle.com,
        richardcochran@...il.com, Mark.Rutland@....com,
        suzuki.poulose@....com, Andre.Przywara@....com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        Steve.Capper@....com, justin.he@....com, jianyong.wu@....com,
        kernel-team@...roid.com
Subject: Re: [PATCH v17 1/7] arm/arm64: Probe for the presence of KVM
 hypervisor

On 2021-02-05 11:19, Will Deacon wrote:
> On Fri, Feb 05, 2021 at 09:11:00AM +0000, Steven Price wrote:
>> On 02/02/2021 14:11, Marc Zyngier wrote:
>> > diff --git a/drivers/firmware/smccc/kvm_guest.c b/drivers/firmware/smccc/kvm_guest.c
>> > new file mode 100644
>> > index 000000000000..23ce1ded88b4
>> > --- /dev/null
>> > +++ b/drivers/firmware/smccc/kvm_guest.c
>> > @@ -0,0 +1,51 @@
>> > +// SPDX-License-Identifier: GPL-2.0
>> > +
>> > +#define pr_fmt(fmt) "smccc: KVM: " fmt
>> > +
>> > +#include <linux/init.h>
>> > +#include <linux/arm-smccc.h>
>> > +#include <linux/kernel.h>
>> > +#include <linux/string.h>
>> > +
>> > +static DECLARE_BITMAP(__kvm_arm_hyp_services, ARM_SMCCC_KVM_NUM_FUNCS) __ro_after_init = { };
>> > +
>> > +void __init kvm_init_hyp_services(void)
>> > +{
>> > +	int i;
>> > +	struct arm_smccc_res res;
>> > +
>> > +	if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_HVC)
>> > +		return;
>> > +
>> > +	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, &res);
>> > +	if (res.a0 != ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_0 ||
>> > +	    res.a1 != ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_1 ||
>> > +	    res.a2 != ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_2 ||
>> > +	    res.a3 != ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_3)
>> > +		return;
>> > +
>> > +	memset(&res, 0, sizeof(res));
>> > +	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID, &res);
>> > +	for (i = 0; i < 32; ++i) {
>> > +		if (res.a0 & (i))
>> > +			set_bit(i + (32 * 0), __kvm_arm_hyp_services);
>> > +		if (res.a1 & (i))
>> > +			set_bit(i + (32 * 1), __kvm_arm_hyp_services);
>> > +		if (res.a2 & (i))
>> > +			set_bit(i + (32 * 2), __kvm_arm_hyp_services);
>> > +		if (res.a3 & (i))
>> > +			set_bit(i + (32 * 3), __kvm_arm_hyp_services);
>> 
>> The bit shifts are missing, the tests should be of the form:
>> 
>> 	if (res.a0 & (1 << i))
>> 
>> Or indeed using a BIT() macro.
> 
> Maybe even test_bit()?

yeah. I'll fix that up, thanks for pointing this out.

       M.
-- 
Jazz is not dead. It just smells funny...