Re: [Qemu-devel] [RFC 1/6] Add bpf support to qemu

From: Sameeh Jubran <sameeh@daynix.com>
To: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>,
	Jason Wang <jasowang@redhat.com>, Yan Vugenfirer <yan@daynix.com>
Subject: Re: [Qemu-devel] [RFC 1/6] Add bpf support to qemu
Date: Mon, 3 Sep 2018 15:18:33 +0300	[thread overview]
Message-ID: <CAKPgXcH+tuHux+Hwjs9_SCnbv874T1VdGpy0-tQZ92K1QM3bOw@mail.gmail.com> (raw)
In-Reply-To: <20180903115926.GB14377@redhat.com>

On Mon, Sep 3, 2018 at 2:59 PM, Daniel P. Berrangé <berrange@redhat.com> wrote:
> On Thu, Aug 30, 2018 at 05:27:03PM +0300, Sameeh Jubran wrote:
>> From: Sameeh Jubran <sjubran@redhat.com>
>>
>> This commit adds the bpf header provided by Linux to Qemu.
>
> s/Qemu/QEMU/
>
>>
>> Signed-off-by: Sameeh Jubran <sjubran@redhat.com>
>> ---
>>  MAINTAINERS                     |  5 +++++
>>  configure                       | 44 +++++++++++++++++++++++++++++++++++++++++
>>  scripts/update-linux-headers.sh |  8 ++++++--
>>  3 files changed, 55 insertions(+), 2 deletions(-)
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 0fb5f38f9f..bf2619239c 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -2126,6 +2126,11 @@ F: hw/rdma/*
>>  F: hw/rdma/vmw/*
>>  F: docs/pvrdma.txt
>>
>> +BPF
>> +M: Sameeh Jubran <sameeh@daynix.com>
>> +S: Maintained
>> +F: linux-headers/linux/bpf.h
>> +
>>  Build and test automation
>>  -------------------------
>>  Build and test automation
>> diff --git a/configure b/configure
>> index a8c4094c87..21edaf59aa 100755
>> --- a/configure
>> +++ b/configure
>> @@ -348,6 +348,7 @@ libattr=""
>>  xfs=""
>>  tcg="yes"
>>  membarrier=""
>> +bpf="no"
>
> This should really default to "", with the check below
> automatically doing the right thing to automatically
> enable/disable it.
>
>>  vhost_net="no"
>>  vhost_crypto="no"
>>  vhost_scsi="no"
>> @@ -1173,6 +1174,10 @@ for opt do
>>    ;;
>>    --enable-membarrier) membarrier="yes"
>>    ;;
>> +  --disable-bpf) bpf="no"
>> +  ;;
>> +  --enable-bpf) bpf="yes"
>> +  ;;
>>    --disable-blobs) blobs="no"
>>    ;;
>>    --with-pkgversion=*) pkgversion="$optarg"
>> @@ -1593,6 +1598,7 @@ disabled with --disable-FEATURE, default is enabled if available:
>>    brlapi          BrlAPI (Braile)
>>    curl            curl connectivity
>>    membarrier      membarrier system call (for Linux 4.14+ or Windows)
>> +  bpf             bpf system calls (for Linux 3.18+)
>>    fdt             fdt device tree
>>    bluez           bluez stack connectivity
>>    kvm             KVM acceleration support
>> @@ -5232,6 +5238,38 @@ else
>>  fi
>>
>>  ##########################################
>> +# check for usable bpf system call
>> +if test "$bpf" = "yes"; then
>
> if test "x$bpf" != "xno"; then
>
>> +    have_bpf=no
>> +    if test "$linux" = "yes" ; then
>> +        cat > $TMPC << EOF
>> +    #include <sys/syscall.h>
>> +    #include "linux/bpf.h"
>> +    #include <unistd.h>
>> +    #include <stdlib.h>
>> +    #include <string.h>
>> +    int main(void) {
>> +        union bpf_attr * attr = NULL;
>> +        syscall(__NR_bpf, BPF_PROG_LOAD, attr, sizeof(attr));
>> +        exit(0);
>> +    }
>> +EOF
>> +        bpf_include="-Iinclude/standard-headers/linux"
>> +        bpf_cflags=""
>> +        bpf_libs=""
>> +        if compile_prog "$bpf_include" "$bpf_libs" ; then
>> +            have_bpf=yes
>> +        fi
>> +    fi
>> +    if test "$have_bpf" = "no"; then
>> +      feature_not_found "bpf" "libelf libs are not available or else \
>> +the bpf system call is not available"
>
> if test "$have_bpf" = "no"; then
>     if test "x$bpf" = "xyes" ;
>     then
>        feature_not_found ....
>     else
>        bpf=no
>     fi
> else
>     bpf=yes
> fi
I'll use the x prefix, for anyone wondering why this is necessary ( I
didn't realize this before), checkout the following explanation:
https://stackoverflow.com/questions/174119/why-do-shell-script-comparisons-often-use-xvar-xyes
>
>> +    fi
>> +else
>> +    bpf=no
>> +fi
>> +
>
> Regards,
> Daniel
> --
> |: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
> |: https://libvirt.org         -o-            https://fstop138.berrange.com :|
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-- 
Respectfully,
Sameeh Jubran
Linkedin
Software Engineer @ Daynix.