linux-kernel - Re: [PATCH net-next v3 0/4] vsock: Add flags field in the vsock address

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Date:   Fri, 11 Dec 2020 19:46:10 +0200
From:   "Paraschiv, Andra-Irina" <andraprs@...zon.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
CC:     netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        David Duncan <davdunc@...zon.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Alexander Graf <graf@...zon.de>,
        Jorgen Hansen <jhansen@...are.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH net-next v3 0/4] vsock: Add flags field in the vsock
 address



On 11/12/2020 17:24, Stefano Garzarella wrote:
>
> Hi Andra,
>
> On Fri, Dec 11, 2020 at 12:32:37PM +0200, Andra Paraschiv wrote:
>> vsock enables communication between virtual machines and the host 
>> they are
>> running on. Nested VMs can be setup to use vsock channels, as the multi
>> transport support has been available in the mainline since the v5.5 
>> Linux kernel
>> has been released.
>>
>> Implicitly, if no host->guest vsock transport is loaded, all the 
>> vsock packets
>> are forwarded to the host. This behavior can be used to setup 
>> communication
>> channels between sibling VMs that are running on the same host. One 
>> example can
>> be the vsock channels that can be established within AWS Nitro Enclaves
>> (see Documentation/virt/ne_overview.rst).
>>
>> To be able to explicitly mark a connection as being used for a 
>> certain use case,
>> add a flags field in the vsock address data structure. The value of 
>> the flags
>> field is taken into consideration when the vsock transport is 
>> assigned. This way
>> can distinguish between different use cases, such as nested VMs / local
>> communication and sibling VMs.
>>
>> The flags field can be set in the user space application connect 
>> logic. On the
>> listen path, the field can be set in the kernel space logic.
>>
>
> I reviewed all the patches and they are in a good shape!

Hi Stefano,

Thanks for the overall review and for the reconfirmation of the Rb for 
the vsock address data structure changes.

>
> Maybe the last thing to add is a flags check in the
> vsock_addr_validate(), to avoid that flags that we don't know how to
> handle are specified.

I can add this validation as a new patch in the series, next revision.

Thanks,
Andra

>
> For example if in the future we add new flags that this version of the
> kernel is not able to satisfy, we should return an error to the
> application.
>
> I mean something like this:
>
>     diff --git a/net/vmw_vsock/vsock_addr.c b/net/vmw_vsock/vsock_addr.c
>     index 909de26cb0e7..73bb1d2fa526 100644
>     --- a/net/vmw_vsock/vsock_addr.c
>     +++ b/net/vmw_vsock/vsock_addr.c
>     @@ -22,6 +22,8 @@ EXPORT_SYMBOL_GPL(vsock_addr_init);
>
>      int vsock_addr_validate(const struct sockaddr_vm *addr)
>      {
>     +       unsigned short svm_valid_flags = VMADDR_FLAG_TO_HOST;
>     +
>             if (!addr)
>                     return -EFAULT;
>
>     @@ -31,6 +33,9 @@ int vsock_addr_validate(const struct sockaddr_vm 
> *addr)
>             if (addr->svm_zero[0] != 0)
>                     return -EINVAL;
>
>     +       if (addr->svm_flags & ~svm_valid_flags)
>     +               return -EINVAL;
>     +
>             return 0;
>      }
>      EXPORT_SYMBOL_GPL(vsock_addr_validate);
>
>
> Thanks,
> Stefano
>
>> Thank you.
>>
>> Andra
>>
>> ---
>>
>> Patch Series Changelog
>>
>> The patch series is built on top of v5.10-rc7.
>>
>> GitHub repo branch for the latest version of the patch series:
>>
>> * https://github.com/andraprs/linux/tree/vsock-flag-sibling-comm-v3
>>
>> v2 -> v3
>>
>> * Rebase on top of v5.10-rc7.
>> * Add "svm_flags" as a new field, not reusing "svm_reserved1".
>> * Update comments to mention when the "VMADDR_FLAG_TO_HOST" flag is 
>> set in the
>>  connect and listen paths.
>> * Update bitwise check logic to not compare result to the flag value.
>> * v2: 
>> https://lore.kernel.org/lkml/20201204170235.84387-1-andraprs@amazon.com/
>>
>> v1 -> v2
>>
>> * Update the vsock flag naming to "VMADDR_FLAG_TO_HOST".
>> * Use bitwise operators to setup and check the vsock flag.
>> * Set the vsock flag on the receive path in the vsock transport 
>> assignment
>>  logic.
>> * Merge the checks for the g2h transport assignment in one "if" block.
>> * v1: 
>> https://lore.kernel.org/lkml/20201201152505.19445-1-andraprs@amazon.com/
>>
>> ---
>>
>> Andra Paraschiv (4):
>>  vm_sockets: Add flags field in the vsock address data structure
>>  vm_sockets: Add VMADDR_FLAG_TO_HOST vsock flag
>>  af_vsock: Set VMADDR_FLAG_TO_HOST flag on the receive path
>>  af_vsock: Assign the vsock transport considering the vsock address
>>    flags
>>
>> include/uapi/linux/vm_sockets.h | 25 ++++++++++++++++++++++++-
>> net/vmw_vsock/af_vsock.c        | 21 +++++++++++++++++++--
>> 2 files changed, 43 insertions(+), 3 deletions(-)
>>
>> -- 
>> 2.20.1 (Apple Git-117)
>>
>>
>>
>>
>> Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. 
>> Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. 
>> Registered in Romania. Registration number J22/2621/2005.
>>
>




Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.