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[60.241.117.97]) by smtp.gmail.com with ESMTPSA id e26sm13057067pfj.61.2020.04.06.21.32.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Apr 2020 21:32:58 -0700 (PDT) Date: Tue, 07 Apr 2020 14:31:28 +1000 From: Nicholas Piggin Subject: Re: [PATCH v2 09/14] powerpc/pseries: limit machine check stack to 4GB To: Christophe Leroy , linuxppc-dev@lists.ozlabs.org References: <20200403132622.130394-1-npiggin@gmail.com> <20200403132622.130394-10-npiggin@gmail.com> <2b114363-7fa9-8383-0b95-93540e00f2a8@c-s.fr> In-Reply-To: <2b114363-7fa9-8383-0b95-93540e00f2a8@c-s.fr> MIME-Version: 1.0 User-Agent: astroid/0.15.0 (https://github.com/astroidmail/astroid) Message-Id: <1586233873.l2apf9xo4a.astroid@bobo.none> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mahesh Salgaonkar , Ganesh Goudar , Mahesh Salgaonkar Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Christophe Leroy's on April 4, 2020 12:19 am: >=20 >=20 > Le 03/04/2020 =C3=A0 15:26, Nicholas Piggin a =C3=A9crit=C2=A0: >> This allows rtas_args to be put on the machine check stack, which >> avoids a lot of complications with re-entrancy deadlocks. >>=20 >> Reviewed-by: Mahesh Salgaonkar >> Signed-off-by: Nicholas Piggin >> --- >> arch/powerpc/kernel/setup_64.c | 17 ++++++++++++++++- >> 1 file changed, 16 insertions(+), 1 deletion(-) >>=20 >> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_= 64.c >> index e05e6dd67ae6..3a2428aa3d9a 100644 >> --- a/arch/powerpc/kernel/setup_64.c >> +++ b/arch/powerpc/kernel/setup_64.c >> @@ -692,6 +692,9 @@ void __init exc_lvl_early_init(void) >> void __init emergency_stack_init(void) >> { >> u64 limit; >> +#ifdef CONFIG_PPC_BOOK3S_64 >=20 > #ifdef not needed, see below >=20 >> + u64 mce_limit; >> +#endif >> unsigned int i; >> =20 >> /* >> @@ -710,6 +713,18 @@ void __init emergency_stack_init(void) >> */ >> limit =3D min(ppc64_bolted_size(), ppc64_rma_size); >> =20 >> + /* >> + * Machine check on pseries calls rtas, but can't use the static >> + * rtas_args due to a machine check hitting while the lock is held. >> + * rtas args have to be under 4GB, so the machine check stack is >> + * limited to 4GB so args can be put on stack. >> + */ >> +#ifdef CONFIG_PPC_BOOK3S_64 >=20 > This ifdef is not needed. FW_FEATURE_LPAR is only possible on=20 > CONFIG_PPC_BOOK3S_64 (indeed only on PSERIES or PS3). On others=20 > firmware_has_feature(FW_FEATURE_LPAR) should return 0 at compile time. Sure I'll remove it. >> + mce_limit =3D limit; >> + if (firmware_has_feature(FW_FEATURE_LPAR) && mce_limit > 4UL*1024*1024= *1024) >> + mce_limit =3D 4UL*1024*1024*1024; >=20 > You should use SZ_4G instead of hardcoding. Will do. Thanks, Nick =