linux-kernel - Re: [PATCH 3/4] KVM: selftests: Use asserting kvm_ioctl() macros when getting ARM page sizes

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Message-ID: <ae42db25-9c8c-3f27-9ccb-41644b135a8b@rbox.co>
Date:   Fri, 4 Aug 2023 16:58:26 +0200
From:   Michal Luczaj <mhal@...x.co>
To:     Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] KVM: selftests: Use asserting kvm_ioctl() macros when
 getting ARM page sizes

On 8/4/23 02:42, Sean Christopherson wrote:
> Use kvm_ioctl() instead of open coding equivalent ioctl()+TEST_ASSERT()
> calls when getting the support page sizes on ARM.  The macro usage is a
> little funky since the "kvm_fd" parameter implies an actual /dev/kvm fd,
> but on the other hand the code is invoking KVM ioctl()s.
> 
> Alternatively, the core utilities could expose a vm_open()+vm_close()
> pair so that the ARM code could create a dummy, on-stack VM+vCPU pair and
> use {vm,vcpu}_ioctl() as appropriate.  But the odds of something breaking
> due to oddball, partial usage of kvm_vm and kvm_vcpu structures is much
> higher than realizing meaningful benefit from using {vm,vcpu}_ioctl().

Since you're doing the cleanup, does mmio_warning_test qualify for the
same (funky usage ahead)?

-       kvm = open("/dev/kvm", O_RDWR);
-       TEST_ASSERT(kvm != -1, "failed to open /dev/kvm");
-       kvmvm = __kvm_ioctl(kvm, KVM_CREATE_VM, NULL);
-       TEST_ASSERT(kvmvm > 0, KVM_IOCTL_ERROR(KVM_CREATE_VM, kvmvm));
-       kvmcpu = ioctl(kvmvm, KVM_CREATE_VCPU, 0);
-       TEST_ASSERT(kvmcpu != -1, KVM_IOCTL_ERROR(KVM_CREATE_VCPU, kvmcpu));
+       kvm = open_path_or_exit(KVM_DEV_PATH, O_RDWR);
+       kvmvm = kvm_fd_ioctl(kvm, KVM_CREATE_VM, NULL);
+       kvmcpu = kvm_fd_ioctl(kvmvm, KVM_CREATE_VCPU, NULL);

Side note, just in case this wasn't your intention: no kvm@ in cc.

thanks,
Michal