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SubjectRe: [PATCH v17 1/7] arm/arm64: Probe for the presence of KVM hypervisor
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()?

Will

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