Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 18 Oct 2019 11:25:19 -0700 (PDT)
From:   Paul Walmsley <paul.walmsley@sifive.com>
To:     Atish Patra <Atish.Patra@wdc.com>
cc:     "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "info@metux.net" <info@metux.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "rfontana@redhat.com" <rfontana@redhat.com>,
        "johan@kernel.org" <johan@kernel.org>,
        "anup@brainfault.org" <anup@brainfault.org>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "palmer@sifive.com" <palmer@sifive.com>,
        "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
        "allison@lohutok.net" <allison@lohutok.net>
Subject: Re: [PATCH v2  2/2] RISC-V: Consolidate isa correctness check
In-Reply-To: <a45f0c0e3db2e852770485bc581d489b6ee7545e.camel@wdc.com>
Message-ID: <alpine.DEB.2.21.9999.1910181121270.21875@viisi.sifive.com>
References: <20191009220058.24964-1-atish.patra@wdc.com>  <20191009220058.24964-3-atish.patra@wdc.com>  <alpine.DEB.2.21.9999.1910180142460.21875@viisi.sifive.com> <a45f0c0e3db2e852770485bc581d489b6ee7545e.camel@wdc.com>
User-Agent: Alpine 2.21.9999 (DEB 301 2018-08-15)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, 18 Oct 2019, Atish Patra wrote:

> On Fri, 2019-10-18 at 01:43 -0700, Paul Walmsley wrote:
> > On Wed, 9 Oct 2019, Atish Patra wrote:
> > 
> > > Currently, isa string is read and checked for correctness at 
> > > multiple places.
> > > 
> > > Consolidate them into one function and use it only during early 
> > > bootup. In case of a incorrect isa string, the cpu shouldn't boot at 
> > > all.
> > > 
> > > Signed-off-by: Atish Patra <atish.patra@wdc.com>
> > 
> > Looks like riscv_read_check_isa() is called twice for each hart.  Is 
> > there any way to call it only once per hart?
> > 
> 
> I had to add the check in riscv_fill_hwcap() because that function is
> iterating over all cpu nodes to set the hwcap. Thus, some of the harts
> that are not available due to incorrect isa string can affect hwcap.
> 
> We can check cpu_possible_mask to figure out the harts with invalid isa
> strings but that will perform poorly as RISC-V have more harts in
> future.

How about just calling riscv_read_check_isa() once for all harts and 
leaving riscv_fill_hwcap() the way it was?  You'll probably need to hoist 
the earlier call out of setup_smp(), so it still is called when 
!CONFIG_SMP.


- Paul