Re: [PATCH 07/16] KVM: arm64: Wire MMIO guard hypercalls
From: Will Deacon <will@kernel.org>
Date: 2021-07-27 18:11:54
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kvm, kvmarm, lkml
On Thu, Jul 15, 2021 at 05:31:50PM +0100, Marc Zyngier wrote:
quoted hunk ↗ jump to hunk
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 | 20 ++++++++++++++++++++ include/linux/arm-smccc.h | 28 ++++++++++++++++++++++++++++ 2 files changed, 48 insertions(+)diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c index 30da78f72b3b..a3deeb907fdd 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 +130,29 @@ 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); + 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: + val[0] = PAGE_SIZE; + break;
I get the nagging feeling that querying the stage-2 page-size outside of MMIO guard is going to be useful once we start looking at memory sharing, so perhaps rename this to something more generic?
+ case ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_ENROLL_FUNC_ID: + 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 (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 (kvm_remove_ioguard_page(vcpu, vcpu_get_reg(vcpu, 1))) + val[0] = SMCCC_RET_SUCCESS; + break;
I think there's a slight discrepancy between MAP and UNMAP here in that calling UNMAP on something that hasn't been mapped will fail, whereas calling MAP on something that's already been mapped will succeed. I think that might mean you can't reason about the final state of the page if two vCPUs race to call these functions in some cases (and both succeed). Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel