Received-SPF: pass (google.com: domain of linux-kernel+bounces-69375-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Date: Fri, 16 Feb 2024 22:46:17 +0100
From: Borislav Petkov <bp@alien8.de>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Xin Li <xin@zytor.com>, Sean Christopherson <seanjc@google.com>,
	Max Kellermann <max.kellermann@ionos.com>, hpa@zytor.com,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	Stephen Rothwell <sfr@canb.auug.org.au>, kvm@vger.kernel.org,
	Arnd Bergmann <arnd@kernel.org>
Subject: Re: [PATCH] arch/x86/entry_fred: don't set up KVM IRQs if KVM is
 disabled
Message-ID: <20240216214617.GBZc_XqVtMuY9_eWWG@fat_crate.local>
References: <20240215133631.136538-1-max.kellermann@ionos.com>
 <Zc5sMmT20kQmjYiq@google.com>
 <a61b113c-613c-41df-80a5-b061889edfdf@zytor.com>
 <5a332064-0a26-4bb9-8a3e-c99604d2d919@redhat.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <5a332064-0a26-4bb9-8a3e-c99604d2d919@redhat.com>
Content-Transfer-Encoding: quoted-printable

+ Arnd for

https://lore.kernel.org/r/20240216202527.2493264-1-arnd@kernel.org

On Fri, Feb 16, 2024 at 07:31:46AM +0100, Paolo Bonzini wrote:
> On 2/16/24 03:10, Xin Li wrote:
> > On 2/15/2024 11:55 AM, Sean Christopherson wrote:
> > > +Paolo and Stephen
> > >=20
> > > FYI, there's a build failure in -next due to a collision between
> > > kvm/next and
> > > tip/x86/fred.=C2=A0 The above makes everything happy.
> > >=20
> > > On Thu, Feb 15, 2024, Max Kellermann wrote:
> > > > When KVM is disabled, the POSTED_INTR_* macros do not exist, and =
the
> > > > build fails.
> > > >=20
> > > > Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code=
")
> > > > Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
> > > > ---
> > > > =C2=A0 arch/x86/entry/entry_fred.c | 2 ++
> > > > =C2=A0 1 file changed, 2 insertions(+)
> > > >=20
> > > > diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_f=
red.c
> > > > index ac120cbdaaf2..660b7f7f9a79 100644
> > > > --- a/arch/x86/entry/entry_fred.c
> > > > +++ b/arch/x86/entry/entry_fred.c
> > > > @@ -114,9 +114,11 @@ static idtentry_t
> > > > sysvec_table[NR_SYSTEM_VECTORS] __ro_after_init =3D {
> > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 SYSVEC(IRQ_WORK_VECTOR,=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 irq_work),
> > > > +#if IS_ENABLED(CONFIG_KVM)
> > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 SYSVEC(POSTED_INTR_VECTOR,=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kvm_posted_intr_ipi),
> > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 SYSVEC(POSTED_INTR_WAKEUP_VECTOR,=C2=
=A0=C2=A0=C2=A0 kvm_posted_intr_wakeup_ipi),
> > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 SYSVEC(POSTED_INTR_NESTED_VECTOR,=C2=
=A0=C2=A0=C2=A0 kvm_posted_intr_nested_ipi),
> > > > +#endif
> > > > =C2=A0 };
> > > > =C2=A0 static bool fred_setup_done __initdata;
> > > > --=20
> > > > 2.39.2
> >=20
> > We want to minimize #ifdeffery (which is why we didn't add any to
> > sysvec_table[]), would it be better to simply remove "#if
> > IS_ENABLED(CONFIG_KVM)" around the the POSTED_INTR_* macros from the
> > Linux-next tree?
> >=20
> > BTW, kvm_posted_intr_*() are defined to NULL if !IS_ENABLED(CONFIG_KV=
M).
>=20
> It is intentional that KVM-related things are compiled out completely
> if !IS_ENABLED(CONFIG_KVM), because then it's also not necessary to hav=
e
>=20
> # define fred_sysvec_kvm_posted_intr_ipi                NULL
> # define fred_sysvec_kvm_posted_intr_wakeup_ipi         NULL
> # define fred_sysvec_kvm_posted_intr_nested_ipi         NULL
>=20
> in arch/x86/include/asm/idtentry.h. The full conflict resultion is
>=20
> diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_fred.c
> index ac120cbdaaf2..660b7f7f9a79 100644
> --- a/arch/x86/entry/entry_fred.c
> +++ b/arch/x86/entry/entry_fred.c
> @@ -114,9 +114,11 @@ static idtentry_t sysvec_table[NR_SYSTEM_VECTORS] =
__ro_after_init =3D {
>      SYSVEC(IRQ_WORK_VECTOR,            irq_work),
> +#if IS_ENABLED(CONFIG_KVM)
>      SYSVEC(POSTED_INTR_VECTOR,        kvm_posted_intr_ipi),
>      SYSVEC(POSTED_INTR_WAKEUP_VECTOR,    kvm_posted_intr_wakeup_ipi),
>      SYSVEC(POSTED_INTR_NESTED_VECTOR,    kvm_posted_intr_nested_ipi),
> +#endif
>  };
>  static bool fred_setup_done __initdata;
> diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idt=
entry.h
> index 749c7411d2f1..758f6a2838a8 100644
> --- a/arch/x86/include/asm/idtentry.h
> +++ b/arch/x86/include/asm/idtentry.h
> @@ -745,10 +745,6 @@ DECLARE_IDTENTRY_SYSVEC(IRQ_WORK_VECTOR,        sy=
svec_irq_work);
>  DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_VECTOR,        sysvec_kvm_posted_i=
ntr_ipi);
>  DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_WAKEUP_VECTOR,    sysvec_kvm_poste=
d_intr_wakeup_ipi);
>  DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_NESTED_VECTOR,    sysvec_kvm_poste=
d_intr_nested_ipi);
> -#else
> -# define fred_sysvec_kvm_posted_intr_ipi        NULL
> -# define fred_sysvec_kvm_posted_intr_wakeup_ipi        NULL
> -# define fred_sysvec_kvm_posted_intr_nested_ipi        NULL
>  #endif
>  #if IS_ENABLED(CONFIG_HYPERV)
>=20
> and it seems to be a net improvement to me.  The #ifs match in
> the .h and .c files, and there are no unnecessary initializers
> in the sysvec_table.

Ok, I'll pick up Max' patch tomorrow and we must remember to tell Linus
during the merge window about this.

Thx.

--=20
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette