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

From: Marc Zyngier <maz@kernel.org>
To: Will Deacon <will@kernel.org>, Steven Price <steven.price@arm.com>
Cc: netdev@vger.kernel.org, yangbo.lu@nxp.com,
	john.stultz@linaro.org, tglx@linutronix.de, pbonzini@redhat.com,
	seanjc@google.com, richardcochran@gmail.com,
	Mark.Rutland@arm.com, suzuki.poulose@arm.com,
	Andre.Przywara@arm.com, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	Steve.Capper@arm.com, justin.he@arm.com, jianyong.wu@arm.com,
	kernel-team@android.com
Subject: Re: [PATCH v17 1/7] arm/arm64: Probe for the presence of KVM hypervisor
Date: Fri, 05 Feb 2021 11:23:37 +0000	[thread overview]
Message-ID: <29f8b6f5faf33472b74ab5f2406c6081@kernel.org> (raw)
In-Reply-To: <20210205111921.GA22109@willie-the-truck>

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...