Re: [dpdk-dev] [EXT] [PATCH 5/6] build: add option for armv8 crypto extension

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

> On Fri, May 03, 2019 at 03:54:09AM +0000, Honnappa Nagarahalli wrote:
> > > >>> On Apr 15, 2019, at 1:13 PM, Honnappa Nagarahalli
> > > >>> <Honnappa.Nagarahalli@arm.com> wrote:
> > > >>>
> > > >>>>>>> Subject: [EXT] [PATCH 5/6] build: add option for armv8
> > > >>>>>>> crypto extension
> > > >>>>>>>
> > > >>>>>>> CONFIG_RTE_MACHINE="armv8a"
> > > >>>>>>> +CONFIG_RTE_ENABLE_ARMV8_CRYPTO=y
> > > >>>>>>
> > > >>>>>> This approach is not scalable. Even, it is not good for
> > > >>>>>> BlueField as you you need to maintain two images.
> > > >>>>>>
> > > >>>>>> Unlike other CPU flags, arm64's crypto cpu flag is really
> _optional_.
> > > >>>>>> Access to crypto instructions is always at under runtime check.
> > > >>>>>> See the following in rte_armv8_pmd.c
> > > >>>>>>
> > > >>>>>>
> > > >>>>>>   /* Check CPU for support for AES instruction set */
> > > >>>>>>   if (!rte_cpu_get_flag_enabled(RTE_CPUFLAG_AES)) {
> > > >>>>>>       ARMV8_CRYPTO_LOG_ERR(
> > > >>>>>>           "AES instructions not supported by CPU");
> > > >>>>>>       return -EFAULT;
> > > >>>>>>   }
> > > >>>>>>
> > > >>>>>>   /* Check CPU for support for SHA instruction set */
> > > >>>>>>   if (!rte_cpu_get_flag_enabled(RTE_CPUFLAG_SHA1) ||
> > > >>>>>>       !rte_cpu_get_flag_enabled(RTE_CPUFLAG_SHA2)) {
> > > >>>>>>       ARMV8_CRYPTO_LOG_ERR(
> > > >>>>>>           "SHA1/SHA2 instructions not supported by CPU");
> > > >>>>>>       return -EFAULT;
> > > >>>>>>   }
> > > >>>>>>
> > > >>>>>> So In order to avoid one more config flags specific to armv8
> > > >>>>>> in meson and makefile build infra And avoid the need for 6/6
> patch.
> > > >>>>>> IMO, # Introduce optional CPU flag scheme in eal. Treat armv8
> > > >>>>>> crypto as optional flag # Skip the eal init check for optional flag.
> > > >>>>>>
> > > >>>>>> Do you see any issues with that approach?
> > > >>>>>
> > > >>>>> I also thought about that approach and that was my number 1
> priority.
> > > >>>>> But, I had one question came to my mind. Maybe, arm people can
> > > >>>>> confirm it. Is it 100% guaranteed that compiler never makes
> > > >>>>> use of any of crypto instructions even if there's no specific
> > > >>>>> asm/intrinsic code?  The crypto extension has aes, pmull,
> > > >>>>> sha1 and sha2. In case of rte_memcpy() for x86, for example,
> > > >>>>> compiler may optimize code using avx512f instructions even
> > > >>>>> though it is written specifically with avx2 intrinsics
> > > >>>>> (__mm256_*) unless avx512f is
> > > >>> disabled.
> > > >>>>>
> > > >>>>> If a complier expert in arm (or anyone else) confirm it is
> > > >>>>> completely **optional**, then I'd love to take that approach for
> sure.
> > > >>>>>
> > > >>>>> Copied dpdk-on-arm ML.
> > > >>>>>
> > > >>>> I do not know the answer, will have to check with the compiler team.
> > > >>>> I will get
> > > >>> back on this.
> > > >>>
> > > >>> Any update yet?
> > > >> Currently, enabling 'crypto' flag will generate the crypto
> > > >> instructions only when crypto intrinsics are used. However, when
> > > >> 'sha3' (part of 8.2 crypto) flag is
> > > >
> > > > The default image is 8.1 spec and except octeontx2 every other SoC
> > > > is
> > I am not following this. I think the default image is 8.0.
> >
> > > > 8.1 and For octeotx2 crypto is supported. If so, Should we worry this
> case?
> > I assume we all are talking about the distro/binary portable build. IMO, we
> should not just look at the existing SoCs.
> > The CPU specific builds have the freedom to compile as per their
> corresponding support.
> >
> > >
> > > Right, it sounds to me that we can disable the option without having
> > > the new config flag until such instructions get needed. According to
> > > gcc-8 release note [1], currently '+crypto' implies '+aes' and
> > > '+sha2' while '+sha3' and '+sm4' are newly introduced. Given that
> > > armv8 crypto PMD uses external binary of Marvell. I don't see any
> > > reason to enable '+crypto'. How about simply disable it from armv8 build
> configs?
> > I think it should be fine. But, this alone is not enough. The run time
> > detection of the crypto feature and hooking up the correct pointers
> > needs to be added.
> 
> Like Jerin pointed out above, armv8 cryptodev already has runtime check of
> cpuflags. If there's no support, it returns error. Unless we need a fallback
> function with non-crypto instructions instead of returning error, I don't think
> such hookup of func pointers are needed.
> 
> > > diff --git a/config/arm/meson.build b/config/arm/meson.build index
> > > 7fa6ed3105..abc8cf346c 100644
> > > --- a/config/arm/meson.build
> > > +++ b/config/arm/meson.build
> > > @@ -74,7 +74,7 @@ flags_octeontx2_extra = [
> > >         ['RTE_USE_C11_MEM_MODEL', true]]
> > >
> > >  machine_args_generic = [
> > > -       ['default', ['-march=armv8-a+crc+crypto']],
> > > +       ['default', ['-march=armv8-a+crc']],
> > >         ['native', ['-march=native']],
> > >         ['0xd03', ['-mcpu=cortex-a53']],
> > >         ['0xd04', ['-mcpu=cortex-a35']], diff --git
> > > a/mk/machine/armv8a/rte.vars.mk b/mk/machine/armv8a/rte.vars.mk
> > > index 8252efbb7b..5e3ffc3adf 100644
> > > --- a/mk/machine/armv8a/rte.vars.mk
> > > +++ b/mk/machine/armv8a/rte.vars.mk
> > > @@ -28,4 +28,4 @@
> > >  # CPU_LDFLAGS =
> > >  # CPU_ASFLAGS =
> > >
> > > -MACHINE_CFLAGS += -march=armv8-a+crc+crypto
> > > +MACHINE_CFLAGS += -march=armv8-a+crc
> > >
> > >
> > > [1]
> > > https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgc
> > > c.gnu.org%2Fgcc-
> 8%2Fchanges.html&amp;data=02%7C01%7Cyskoh%40mellanox
> > > .com%7C5cd398e4cf1e45c1755a08d6cf7b0091%7Ca652971c7d2e4d9ba
> 6a4d14925
> > >
> 6f461b%7C0%7C0%7C636924524543262594&amp;sdata=4m4S2VQUVBML
> YqpxmeLoAP
> > > qAcKGm9u1Wo5R7oE2CK94%3D&amp;reserved=0
> > >
> > > Thanks,
> > > Yongseok
> > >
> > > >> enabled, compiler can generate 3-way exclusive OR instructions
> > > >> beyond the intrinsics.
> > > >
> > > > The very same problem will be applicable for Linux kernel too for
> > > distribution binary case.
> > > > If the above statement is true about 8.2 crypto and crypto
> > > > generation without Intrinsics then we need to see how linux kernel
> > > > handling that and align our solution based on that.
> > Yes, the compiler team cited Linux kernel example, I have not verified it
> myself.
> >
> > > >
> > > >> Compiler team cannot provide a guarantee that other crypto
> > > >> instructions will not be used beyond the intrinsics.
> > > >>
> > > >> The current suggestion is to use GNU indirect function [1] or
> > > >> similar. I am not
> > > >
> > > > Not sure how it helps? If we know the compiler is generating a
> > > > specific function With crypto instruction then we can generate
> > > > _alternative_ function for the same With hwcap?.How do we know
> > > > which function compiler using compiler instructions?
> > This feature is similar to using function pointers and choosing which
> > function pointer to use at run time. If this feature is used, the
> > function pointer to use is decided during dynamic linking stage.
> 
> I think what Jerin meant was about the case where compiler can generate
> crypto instructions beyond intrinsics/asm like sha3 for 3-way exclusive OR
> instructions. In this case, such function pointer can't help as we can't know
> how compiler generates such instructions.
> 
> > Either ways, we need to have 2 sets of crypto PMD drivers. One that
> > implements the actual functionality using crypto intrinsics/assembly.
> > Only, this code needs to be compiled with '+crypto'. Second driver
> > that implements just stubs and returns error. This code will be
> > compiled without '+crypto'. At run time, depending on the HWCAP, the
> > correct driver/function pointers need to be hooked up.
> 
> Like I mentioned above, it may not be necessary. armv8 cryptodev links
> external library, which is compiled separately (out of dpdk) with crypto
> support and we don't have/need a fallback but returns error if no crypto
> support in runtime.
Ok, got it (did not realize crypto library is external to DPDK).

> 
> > > >> sure on GNU indirect function portability.
> > > >
> > > > We are using HWCAP scheme, So we may not need the very exact GNU
> > > > indirect scheme to fix the issue.
> > Agree, using indirect functions is not a must.
> >
> > > >
> > > >>
> > > >> [1]
> > > >> https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2
> > > >> Fwil
> > > >> lnewton.name%2F2013%2F07%2F02%2Fusing-gnu-indirect-
> > > functions%2F&amp;d
> > > >>
> > >
> ata=02%7C01%7Cyskoh%40mellanox.com%7Cda8fb7ed03e7406ded8908d6c
> > > ee6d759
> > > >> %7Ca652971c7d2e4d9ba6a4d149256f461b%7C0%7C0%7C63692388
> 818
> > > 9316743&amp;
> > > >>
> > >
> sdata=x5XNd5WZ3EtiprPMiFzaskvigX8K0AoXA2w%2BKiN156c%3D&amp;res
> > > erved=0