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Tue, 12 Jan 2021 04:20:58 -0800 (PST) Received: from [10.57.39.145] (unknown [10.57.39.145]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 180C23F66E; Tue, 12 Jan 2021 04:20:54 -0800 (PST) Subject: Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility To: Marc Zyngier References: <20210111132811.2455113-1-maz@kernel.org> <20210111132811.2455113-10-maz@kernel.org> <20210111184154.GC17941@gaia> <129db8bd3913a90c96d4cfe4f55e27a0@kernel.org> From: Suzuki K Poulose Message-ID: <7720a317-2591-3b60-41ce-772bf168bee7@arm.com> Date: Tue, 12 Jan 2021 12:20:45 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-GB Cc: Prasad Sodagudi , Srinivas Ramana , kernel-team@android.com, Catalin Marinas , linux-kernel@vger.kernel.org, Ard Biesheuvel , Ajay Patil , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: base64 Content-Type: text/plain; charset="utf-8"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu T24gMS8xMi8yMSAxMTo1MSBBTSwgTWFyYyBaeW5naWVyIHdyb3RlOgo+IE9uIDIwMjEtMDEtMTIg MTE6NTAsIE1hcmMgWnluZ2llciB3cm90ZToKPj4gSGkgU3V6dWtpLAo+Pgo+PiBPbiAyMDIxLTAx LTEyIDA5OjE3LCBTdXp1a2kgSyBQb3Vsb3NlIHdyb3RlOgo+Pj4gSGkgTWFyYywKPj4+Cj4+PiBP biAxLzExLzIxIDc6NDggUE0sIE1hcmMgWnluZ2llciB3cm90ZToKPj4KPj4gWy4uLl0KPj4KPj4+ PiBkaWZmIC0tZ2l0IGEvYXJjaC9hcm02NC9rZXJuZWwvY3B1ZmVhdHVyZS5jIGIvYXJjaC9hcm02 NC9rZXJuZWwvY3B1ZmVhdHVyZS5jCj4+Pj4gaW5kZXggODk0YWY2MGI5NjY5Li4wMGQ5OWU1OTNi NjUgMTAwNjQ0Cj4+Pj4gLS0tIGEvYXJjaC9hcm02NC9rZXJuZWwvY3B1ZmVhdHVyZS5jCj4+Pj4g KysrIGIvYXJjaC9hcm02NC9rZXJuZWwvY3B1ZmVhdHVyZS5jCj4+Pj4gQEAgLTc3NCw2ICs3NzQs NyBAQCBzdGF0aWMgdm9pZCBfX2luaXQgaW5pdF9jcHVfZnRyX3JlZyh1MzIgc3lzX3JlZywgdTY0 IG5ldykKPj4+PiDCoMKgwqDCoMKgIHU2NCBzdHJpY3RfbWFzayA9IH4weDBVTEw7Cj4+Pj4gwqDC oMKgwqDCoCB1NjQgdXNlcl9tYXNrID0gMDsKPj4+PiDCoMKgwqDCoMKgIHU2NCB2YWxpZF9tYXNr ID0gMDsKPj4+PiArwqDCoMKgIHU2NCBvdmVycmlkZV92YWwgPSAwLCBvdmVycmlkZV9tYXNrID0g MDsKPj4+Pgo+Pj4+IMKgwqDCoMKgwqAgY29uc3Qgc3RydWN0IGFybTY0X2Z0cl9iaXRzICpmdHJw Owo+Pj4+IMKgwqDCoMKgwqAgc3RydWN0IGFybTY0X2Z0cl9yZWcgKnJlZyA9IGdldF9hcm02NF9m dHJfcmVnKHN5c19yZWcpOwo+Pj4+IEBAIC03ODEsOSArNzgyLDM1IEBAIHN0YXRpYyB2b2lkIF9f aW5pdCBpbml0X2NwdV9mdHJfcmVnKHUzMiBzeXNfcmVnLCB1NjQgbmV3KQo+Pj4+IMKgwqDCoMKg wqAgaWYgKCFyZWcpCj4+Pj4gwqDCoMKgwqDCoMKgwqDCoMKgIHJldHVybjsKPj4+Pgo+Pj4+ICvC oMKgwqAgaWYgKHJlZy0+b3ZlcnJpZGVfbWFzayAmJiByZWctPm92ZXJyaWRlX3ZhbCkgewo+Pj4+ ICvCoMKgwqDCoMKgwqDCoCBvdmVycmlkZV9tYXNrID0gKnJlZy0+b3ZlcnJpZGVfbWFzazsKPj4+ PiArwqDCoMKgwqDCoMKgwqAgb3ZlcnJpZGVfdmFsID0gKnJlZy0+b3ZlcnJpZGVfdmFsOwo+Pj4+ ICvCoMKgwqAgfQo+Pj4+ICsKPj4+PiDCoMKgwqDCoMKgIGZvciAoZnRycCA9IHJlZy0+ZnRyX2Jp dHM7IGZ0cnAtPndpZHRoOyBmdHJwKyspIHsKPj4+PiDCoMKgwqDCoMKgwqDCoMKgwqAgdTY0IGZ0 cl9tYXNrID0gYXJtNjRfZnRyX21hc2soZnRycCk7Cj4+Pj4gwqDCoMKgwqDCoMKgwqDCoMKgIHM2 NCBmdHJfbmV3ID0gYXJtNjRfZnRyX3ZhbHVlKGZ0cnAsIG5ldyk7Cj4+Pj4gK8KgwqDCoMKgwqDC oMKgIHM2NCBmdHJfb3ZyID0gYXJtNjRfZnRyX3ZhbHVlKGZ0cnAsIG92ZXJyaWRlX3ZhbCk7Cj4+ Pj4gKwo+Pj4+ICvCoMKgwqDCoMKgwqDCoCBpZiAoKGZ0cl9tYXNrICYgb3ZlcnJpZGVfbWFzaykg PT0gZnRyX21hc2spIHsKPj4+PiArwqDCoMKgwqDCoMKgwqDCoMKgwqDCoCBpZiAoZnRyX292ciA8 IGZ0cl9uZXcpIHsKPj4+Cj4+PiBIZXJlIHdlIGFzc3VtZSB0aGF0IGFsbCB0aGUgZmVhdHVyZXMg YXJlIEZUUl9MT1dFUl9TQUZFLiBXZSBjb3VsZAo+Pj4gcHJvYmFibHkgdXNlIGFybTY0X2Z0cl9z YWZlX3ZhbHVlKGZ0cnAsIGZ0cl9uZXcsIGZ0cl9vdnIpIGhlcmUgPwo+Pj4gVGhhdCB3b3VsZCBj b3ZlciB1cyBmb3IgYm90aCBISUdIRVJfU0FGRSBhbmQgTE9XRVJfU0FGRSBmZWF0dXJlcy4KPj4+ IEhvd2V2ZXIgdGhhdCBtYXkgYmUgcmVzdHJpY3RpdmUgZm9yIEZUUl9FWEFDVCwgYXMgd2UgdGhl IHNhZmUKPj4+IHZhbHVlIHdvdWxkIGJlIHNldCB0byAiZnRyLT5zYWZlX3ZhbCIuIEkgZ3Vlc3Mg dGhhdCBtYXkgYmUgYmV0dGVyCj4+PiB0aGFuIGZvcmNpbmcgdG8gdXNlIGFuIHVuc2FmZSB2YWx1 ZSBmb3IgdGhlIGJvb3QgQ1BVLCB3aGljaCBjb3VsZAo+Pj4gYW55d2F5IGNvbmZsaWN0IHdpdGgg dGhlIG90aGVyIENQVXMgYW5kIGV2ZW50dWFsbHkgdHJpZ2dlciB0aGUKPj4+IGZ0ciBhbHVlIHRv IGJlIHNhZmVfdmFsLgo+Pgo+PiBJIGxpa2UgdGhlIGlkZWEgb2YgdXNpbmcgdGhlIGhlbHBlciwg YXMgaXQgY2xlYW51cHMgdXAgdGhlIGNvZGUgYSBiaXQuCj4+IEhvd2V2ZXIsIG5vdCBiZWluZyB0 byBzZXQgYSBmZWF0dXJlIHRvIGEgY2VydGFpbiB2YWx1ZSBjb3VsZCBiZSByZXN0cmljdGl2ZSwK Pj4gYXMgaW4gZ2VuZXJhbCwgaXQgbWVhbnMgdGhhdCB3ZSBjYW4gb25seSBkaXNhYmxlIGEgZmVh dHVyZSBhbmQgbm90IGFkanVzdAo+PiBpdHMgbGV2ZWwgb2Ygc3VwcG9ydC4KPj4KPj4gVGFrZSBQ TVVWRVIgZm9yIGV4YW1wbGU6IHdpdGggdGhlIGhlbHBlciwgSSBjYW4ndCBvdmVycmlkZSBpdCBm cm9tIHY4LjQgdG8KPj4gdjguMS4gSSBjYW4gb25seSBnbyB0byB2OC4wLgo+IAo+IEFjdHVhbGx5 LCB3ZSBjYW4gb25seSAqZGlzYWJsZSogdGhlIFBNVSBhbHRvZ2V0aGVyLiBTYW1lIHF1ZXN0aW9u IHRob3VnaC4uLgoKSXQgZGVwZW5kcyBvbiB0d28gdGhpbmdzIDoKCjEpIFdoYXQgaXMgdGhlIHNh ZmUgdmFsdWUgZm9yIGFuIEVYQUNUIHR5cGVkIGZlYXR1cmUgPwpVc3VhbGx5LCB0aGF0IG1lYW5z IGVpdGhlciBkaXNhYmxlZCwgb3IgdGhlIGxvd2VzdCBwb3NzaWJsZSB2YWx1ZS4KCjIpIEhvdyBp cyB0aGlzIHZhbHVlIGNvbnN1bWVkID8KICAgYSkgaS5lLCBEbyB3ZSB1c2UgdGhlIHBlci1DUFUg dmFsdWUKCVRoZW4gbm9uZSBvZiB0aGVzZSBjaGFuZ2VzIGhhdmUgYW55IGVmZmVjdAogICBiKSBT eXN0ZW0gd2lkZSB2YWx1ZSA/CiAgICAgICBUaGVuIHdlIGdldCB0aGUgc2FmZSB2YWx1ZSBhcyAi aW5mbHVlbmNlZCIgYnkgdGhlIGluZnJhc3RydWN0dXJlLgoKVGhlIHNhZmUgdmFsdWUgd2UgdXNl IGZvciBFWEFDVCBmZWF0dXJlcyBpcyBleGNsdXNpdmVseSBmb3IgbWFraW5nIHN1cmUKdGhhdCB0 aGUgc3lzdGVtIHVzZXMgdGhlIHNhZmUgYXNzdW1wdGlvbiBhbmQgdGh1cyBzaG91bGQgYmUgdGhl IGJlc3QKb3B0aW9uLgoKVG8gYW5zd2VyIHlvdXIgcXVlc3Rpb24sIGZvciBQTVUsIGl0IGlzIDAs IGltcGxpZXMsIHY4LjAuIE9yIHdlIGNvdWxkCnVwZGF0ZSB0aGUgc2FmZSB2YWx1ZSB0byAtMSAo MHhmKSBhcyB0aGUgc2FmZSB2YWx1ZSwgd2hpY2ggaXMgYSBiaXQgbW9yZSBzYWZlciwKa2luZCBv ZiBpbXBseWluZyB0aGF0IHRoZSBQTVUgaXMgbm90IGEgc3RhbmRhcmQgb25lLgoKCkNoZWVycwpT dXp1a2kKCgoKPiAKPiAgwqDCoMKgwqDCoMKgwqAgTS4KPiAKPj4KPj4gSXMgaXQgc29tZXRoaW5n IHdlIGNhcmUgYWJvdXQ/Cj4+Cj4+IFRoYW5rcywKPj4KPj4gwqDCoMKgwqDCoMKgwqAgTS4KPiAK Cl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCmt2bWFybSBt YWlsaW5nIGxpc3QKa3ZtYXJtQGxpc3RzLmNzLmNvbHVtYmlhLmVkdQpodHRwczovL2xpc3RzLmNz LmNvbHVtYmlhLmVkdS9tYWlsbWFuL2xpc3RpbmZvL2t2bWFybQo=