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Szmigiero" , Like Xu , open list , "open list:KERNEL VIRTUAL MACHINE (KVM)" Subject: Re: [RFC PATCH 1/4] KVM: selftests: Add support for creating non-default type VMs Message-ID: <20210728201141.6quhfym7tbg2dier@gator> References: <20210726183816.1343022-1-erdemaktas@google.com> <20210726183816.1343022-2-erdemaktas@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Wed, Jul 28, 2021 at 04:07:19PM +0000, David Matlack wrote: > On Tue, Jul 27, 2021 at 08:47:44PM +0000, Sean Christopherson wrote: > > On Mon, Jul 26, 2021, David Matlack wrote: > > > On Mon, Jul 26, 2021 at 11:37:54AM -0700, Erdem Aktas wrote: > > > > Currently vm_create function only creates KVM_X86_LEGACY_VM type VMs. > > > > Changing the vm_create function to accept type parameter to create > > > > new VM types. > > > > > > > > Signed-off-by: Erdem Aktas > > > > Reviewed-by: Sean Christopherson > > > > *-by tags should not be added unless explicitly provided. IIRC, our internal > > gerrit will convert +1 to Reviewed-by, but I don't think that's the case here. > > This applies to all patches in this series. > > > > See "Using Reported-by:, Tested-by:, Reviewed-by:, Suggested-by: and Fixes:" in > > Documentation/process/submitting-patches.rst for more info. > > > > > > Reviewed-by: Peter Gonda > > > > Reviewed-by: Marc Orr > > > > Reviewed-by: Sagi Shahar > > > > > > Reviewed-by: David Matlack > > > > > > (aside from the nit below) > > > > > > > --- > > > > .../testing/selftests/kvm/include/kvm_util.h | 1 + > > > > tools/testing/selftests/kvm/lib/kvm_util.c | 29 +++++++++++++++++-- > > > > 2 files changed, 27 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h > > > > index d53bfadd2..c63df42d6 100644 > > > > --- a/tools/testing/selftests/kvm/include/kvm_util.h > > > > +++ b/tools/testing/selftests/kvm/include/kvm_util.h > > > > @@ -88,6 +88,7 @@ int vcpu_enable_cap(struct kvm_vm *vm, uint32_t vcpu_id, > > > > void vm_enable_dirty_ring(struct kvm_vm *vm, uint32_t ring_size); > > > > > > > > struct kvm_vm *vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm); > > > > +struct kvm_vm *__vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm, int type); > > > > > > nit: Consider using a more readable function name such as > > > vm_create_with_type(). > > > > Ha! This is why I don't like doing internal reviews :-D > > +1 :) > > > > > Erdem originally had vm_create_type(), I suggested __vm_create() as the double > > underscore scheme is more common in the kernel for cases where there's a default > > wrapper and an inner helper that implements the full API. > > > > Convention aside, the argument againsts ...with_type() are that it doesn't scale, > > e.g. if someone adds another parameter parameter for which vm_create() provides a > > default, and it doesn't self-document the relationship between vm_create() and > > the inner helper, e.g. by convention, based on names alone I know that vm_create() > > likely is a wrapper around __vm_create(). > > True, although with __vm_create() is not solving the scalability > problem, it's just preventing scaling altogether (you can only have 1 > wrapper function, vm_create). So if any caller wants to override one of > the defaults they have to override all of them. > > I agree with you though in this case: __vm_create() is a better choice > (especially given the existence of vm_create_with_vcpus). > > A better option than both (but would involve more work) would be to > create an options struct with all optional arguments. Unfortunately C > makes working with options structs a bit clumsy. But it's something to > consider as the number of options passed to __vm_create increases. > > For example: > > struct vm_options { > enum vm_guest_mode mode; > uint64_t phy_pages; > int perm; > int type; > }; > > struct kvm_vm *vm_create(const struct vm_options *options) > { > ... > } > > static const struct vm_options default_vm_options = { > .mode = VM_MODE_DEFAULT, > .phy_pages = DEFAULT_GUEST_PHY_PAGES, > .perm = O_RDWR, > .type = DEFAULT_VM_TYPE, > }; > > /* Create a VM with default options. */ > vm = create_vm(&default_vm_options); > > /* Create a VM with TDX enabled. */ > struct vm_options options = default_vm_options; > options.type = VM_TYPE_TDX; > vm = create_vm(&options); I like this. Thanks, drew