Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Sun, 4 Sep 2022 23:54:15 +0800
From:   Zhao Liu <zhao1.liu@linux.intel.com>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        "Fabio M. De Francesco" <fmdefrancesco@gmail.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Zhenyu Wang <zhenyu.z.wang@intel.com>,
        Zhao Liu <zhao1.liu@intel.com>
Subject: Re: [PATCH] KVM: SVM: Replace kmap_atomic() with kmap_local_page()
Message-ID: <YxTKJ0O3Gd6at5lH@liuzhao-OptiPlex-7080>
References: <20220902090811.2430228-1-zhao1.liu@linux.intel.com>
 <e08c8c46-2aa8-3cb4-dce6-61d64c6835cb@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <e08c8c46-2aa8-3cb4-dce6-61d64c6835cb@intel.com>
Precedence: bulk

On Fri, Sep 02, 2022 at 08:09:29AM -0700, Dave Hansen wrote:
> This changelog is a little on the weak side.  You could literally take
> any arbitrary call-site and file for kmap_atomic() and slap that
> changelog on it.  For instance:
> 
> 	In drivers/target/target_core_sbc.c, the function
> 	sbc_dif_copy_prot() doesn't need to disable pagefaults and
> 	preemption in kmap_atomic(). It can simply use kmap_local_page()
> 	/ kunmap_local() that can instead do the mapping / unmapping
> 	regardless of the context.
> 
> 	With kmap_local_page(), the mapping is per thread, CPU local and
> 	not globally visible. Therefore, sbc_dif_copy_prot() is a
> 	function where the use of kmap_local_page() in place of
> 	kmap_atomic() is correctly suited.
> 
> That's all valid English and there's nothing incorrect in it.  But, it
> doesn't indicate that any actual analysis was performed.  It's utterly
> generic.  It could literally have been generated by a pretty trivial script.
> 
> It would be great to add at least a small, call-site-specific human
> touch to these changelogs.
> 
> In this case, saying something about how global the cache flush is would
> be a great addition.
Thanks Dave! I'll add more detail to the commit message and avoid overly
templated changelogs.

Zhao