Re: [PATCH v2 07/16] KVM: arm64: Wire MMIO guard hypercalls

From: Andrew Jones <drjones@redhat.com>
To: Marc Zyngier <maz@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, will@kernel.org,
	qperret@google.com, dbrazdil@google.com,
	Steven Price <steven.price@arm.com>,
	Fuad Tabba <tabba@google.com>,
	Srivatsa Vaddagiri <vatsa@codeaurora.org>,
	Shanker R Donthineni <sdonthineni@nvidia.com>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	kernel-team@android.com
Subject: Re: [PATCH v2 07/16] KVM: arm64: Wire MMIO guard hypercalls
Date: Thu, 7 Oct 2021 15:53:03 +0200	[thread overview]
Message-ID: <20211007135303.rbyvltetm3h4sqyy@gator> (raw)
In-Reply-To: <20211004174849.2831548-8-maz@kernel.org>

On Mon, Oct 04, 2021 at 06:48:40PM +0100, Marc Zyngier wrote:
> Plumb in the hypercall interface to allow a guest to discover,
> enroll, map and unmap MMIO regions.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/hypercalls.c | 28 ++++++++++++++++++++++++++++
>  include/linux/arm-smccc.h   | 28 ++++++++++++++++++++++++++++
>  2 files changed, 56 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index 30da78f72b3b..c39aab55ecae 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -5,6 +5,7 @@
>  #include <linux/kvm_host.h>
>  
>  #include <asm/kvm_emulate.h>
> +#include <asm/kvm_mmu.h>
>  
>  #include <kvm/arm_hypercalls.h>
>  #include <kvm/arm_psci.h>
> @@ -129,10 +130,37 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
>  	case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
>  		val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES);
>  		val[0] |= BIT(ARM_SMCCC_KVM_FUNC_PTP);
> +		/* Only advertise MMIO guard to 64bit guests */
> +		if (!vcpu_mode_is_32bit(vcpu)) {
> +			val[0] |= BIT(ARM_SMCCC_KVM_FUNC_MMIO_GUARD_INFO);
> +			val[0] |= BIT(ARM_SMCCC_KVM_FUNC_MMIO_GUARD_ENROLL);
> +			val[0] |= BIT(ARM_SMCCC_KVM_FUNC_MMIO_GUARD_MAP);
> +			val[0] |= BIT(ARM_SMCCC_KVM_FUNC_MMIO_GUARD_UNMAP);
> +		}
>  		break;
>  	case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
>  		kvm_ptp_get_time(vcpu, val);
>  		break;
> +	case ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_INFO_FUNC_ID:
> +		if (!vcpu_mode_is_32bit(vcpu))
> +			val[0] = PAGE_SIZE;
> +		break;
> +	case ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_ENROLL_FUNC_ID:
> +		if (!vcpu_mode_is_32bit(vcpu)) {
> +			set_bit(KVM_ARCH_FLAG_MMIO_GUARD, &vcpu->kvm->arch.flags);
> +			val[0] = SMCCC_RET_SUCCESS;
> +		}
> +		break;
> +	case ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_MAP_FUNC_ID:
> +		if (!vcpu_mode_is_32bit(vcpu) &&
> +		    kvm_install_ioguard_page(vcpu, vcpu_get_reg(vcpu, 1)))
> +			val[0] = SMCCC_RET_SUCCESS;
> +		break;
> +	case ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_UNMAP_FUNC_ID:
> +		if (!vcpu_mode_is_32bit(vcpu) &&
> +		    kvm_remove_ioguard_page(vcpu, vcpu_get_reg(vcpu, 1)))
> +			val[0] = SMCCC_RET_SUCCESS;
> +		break;

Since these are all ARM_SMCCC_SMC_64 calls, can we do some sort of
refactoring first, similar to Oliver's "KVM: arm64: Clean up SMC64 PSCI
filtering for AArch32 guests", which would avoid the need for all the
!vcpu_mode_is_32bit's?

>  	case ARM_SMCCC_TRNG_VERSION:
>  	case ARM_SMCCC_TRNG_FEATURES:
>  	case ARM_SMCCC_TRNG_GET_UUID:
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 7d1cabe15262..4aab2078d8d3 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -107,6 +107,10 @@
>  /* KVM "vendor specific" services */
>  #define ARM_SMCCC_KVM_FUNC_FEATURES		0
>  #define ARM_SMCCC_KVM_FUNC_PTP			1
> +#define ARM_SMCCC_KVM_FUNC_MMIO_GUARD_INFO	2
> +#define ARM_SMCCC_KVM_FUNC_MMIO_GUARD_ENROLL	3
> +#define ARM_SMCCC_KVM_FUNC_MMIO_GUARD_MAP	4
> +#define ARM_SMCCC_KVM_FUNC_MMIO_GUARD_UNMAP	5
>  #define ARM_SMCCC_KVM_FUNC_FEATURES_2		127
>  #define ARM_SMCCC_KVM_NUM_FUNCS			128
>  
> @@ -133,6 +137,30 @@
>  #define KVM_PTP_VIRT_COUNTER			0
>  #define KVM_PTP_PHYS_COUNTER			1
>  
> +#define ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_INFO_FUNC_ID		\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_64,				\
> +			   ARM_SMCCC_OWNER_VENDOR_HYP,			\
> +			   ARM_SMCCC_KVM_FUNC_MMIO_GUARD_INFO)
> +
> +#define ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_ENROLL_FUNC_ID		\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_64,				\
> +			   ARM_SMCCC_OWNER_VENDOR_HYP,			\
> +			   ARM_SMCCC_KVM_FUNC_MMIO_GUARD_ENROLL)
> +
> +#define ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_MAP_FUNC_ID			\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_64,				\
> +			   ARM_SMCCC_OWNER_VENDOR_HYP,			\
> +			   ARM_SMCCC_KVM_FUNC_MMIO_GUARD_MAP)
> +
> +#define ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_UNMAP_FUNC_ID		\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_64,				\
> +			   ARM_SMCCC_OWNER_VENDOR_HYP,			\
> +			   ARM_SMCCC_KVM_FUNC_MMIO_GUARD_UNMAP)
> +
>  /* Paravirtualised time calls (defined by ARM DEN0057A) */
>  #define ARM_SMCCC_HV_PV_TIME_FEATURES				\
>  	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
> -- 
> 2.30.2
>

Besides the refactoring suggestion,

Reviewed-by: Andrew Jones <drjones@redhat.com>

Thanks,
drew

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