Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Sat, 31 Jul 2021 09:17:37 +0200
From:   Joerg Roedel <jroedel@suse.de>
To:     Sean Christopherson <seanjc@google.com>
Cc:     Joerg Roedel <joro@8bytes.org>, x86@kernel.org,
        Eric Biederman <ebiederm@xmission.com>,
        kexec@lists.infradead.org, hpa@zytor.com,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Jiri Slaby <jslaby@suse.cz>,
        Dan Williams <dan.j.williams@intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Juergen Gross <jgross@suse.com>,
        Kees Cook <keescook@chromium.org>,
        David Rientjes <rientjes@google.com>,
        Cfir Cohen <cfir@google.com>,
        Erdem Aktas <erdemaktas@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Mike Stunes <mstunes@vmware.com>,
        Martin Radev <martin.b.radev@gmail.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 11/12] x86/sev: Handle CLFLUSH MMIO events
Message-ID: <YQT5Ec5M6maZdFoO@suse.de>
References: <20210721142015.1401-1-joro@8bytes.org>
 <20210721142015.1401-12-joro@8bytes.org>
 <YQSAVo0CXUKHXdLF@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YQSAVo0CXUKHXdLF@google.com>
Precedence: bulk

Hi Sean,

On Fri, Jul 30, 2021 at 10:42:30PM +0000, Sean Christopherson wrote:
> On Wed, Jul 21, 2021, Joerg Roedel wrote:
> This wording can be misread as "the hypervisor is responsible for _all_ cache
> management".  Maybe just:
> 
> 		/*
> 		 * Ignore CLFLUSHes - the hyperivsor is responsible for cache
> 		 * management of emulated MMIO.
> 		 */

Right, will update the comment, thanks.

> Side topic, out of curisoity, what's mapping/accessing emulated MMIO as non-UC?

The CLFLUSHes happen when the kexec'ed kernel maps the VGA framebuffer
as unencrypted. Initially it is mapped encrypted and before re-mapping
the kernel flushes the range from the caches.

I have not investigated why this doesn't happen on the first boot,
though.

Regards,

	Joerg