Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Date:   Tue, 26 Apr 2022 21:51:18 +0200
From:   Heiko Carstens <hca@linux.ibm.com>
To:     Borislav Petkov <bp@alien8.de>
Cc:     Juergen Gross <jgross@suse.com>, linux-kernel@vger.kernel.org,
        x86@kernel.org, linux-arch@vger.kernel.org,
        linux-s390@vger.kernel.org, linux-hyperv@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Arnd Bergmann <arnd@arndb.de>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Christoph Hellwig <hch@infradead.org>,
        Oleksandr Tyshchenko <olekstysh@gmail.com>
Subject: Re: [PATCH 2/2] virtio: replace
 arch_has_restricted_virtio_memory_access()
Message-ID: <YmhNNrLW+tM2gnZB@osiris>
References: <20220426134021.11210-1-jgross@suse.com>
 <20220426134021.11210-3-jgross@suse.com>
 <Ymgtb2dSNYz7DBqx@zn.tnic>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Ymgtb2dSNYz7DBqx@zn.tnic>
Precedence: bulk

On Tue, Apr 26, 2022 at 07:35:43PM +0200, Borislav Petkov wrote:
> On Tue, Apr 26, 2022 at 03:40:21PM +0200, Juergen Gross wrote:
> >  /* protected virtualization */
> >  static void pv_init(void)
> >  {
> >  	if (!is_prot_virt_guest())
> >  		return;
> >  
> > +	platform_set_feature(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
> 
> Kinda long-ish for my taste. I'll probably call it:
> 
> 	platform_set()
> 
> as it is implicit that it sets a feature bit.

...and platform_clear(), instead of platform_reset_feature() please.

> In any case, yeah, looks ok at a quick glance. It would obviously need
> for more people to look at it and say whether it makes sense to them and
> whether that's fine to have in generic code but so far, the experience
> with cc_platform_* says that it seems to work ok in generic code.

We _could_ convert s390's machine flags to this mechanism. Those flags
are historically per-cpu, but if I'm not mistaken none of them is
performance critical anymore, and those who are could/should probably
transformed to jump labels or alternatives anyway.