From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5DEBC4338F for ; Fri, 13 Aug 2021 17:35:53 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7AAA56109E for ; Fri, 13 Aug 2021 17:35:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 7AAA56109E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; 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Fri, 13 Aug 2021 17:33:59 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mEb44-00DGvm-Pj for linux-arm-kernel@lists.infradead.org; Fri, 13 Aug 2021 17:33:56 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2D71761038; Fri, 13 Aug 2021 17:33:52 +0000 (UTC) Received: from 109-170-232-56.xdsl.murphx.net ([109.170.232.56] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mEb41-004qYd-UR; Fri, 13 Aug 2021 18:33:50 +0100 Date: Fri, 13 Aug 2021 18:33:58 +0100 Message-ID: <87k0kp1c6x.wl-maz@kernel.org> From: Marc Zyngier To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Florian Fainelli , bcm-kernel-feedback-list@broadcom.com, kernel-team@android.com Subject: Re: [PATCH 3/5] arm64: Detect disabled HVC early In-Reply-To: <20210813090539.GA7536@willie-the-truck> References: <20210812190213.2601506-1-maz@kernel.org> <20210812190213.2601506-4-maz@kernel.org> <20210813090539.GA7536@willie-the-truck> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 109.170.232.56 X-SA-Exim-Rcpt-To: will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, zajec5@gmail.com, catalin.marinas@arm.com, mark.rutland@arm.com, ardb@kernel.org, f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210813_103352_908134_EC4B75DD X-CRM114-Status: GOOD ( 32.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gRnJpLCAxMyBBdWcgMjAyMSAxMDowNTo0MCArMDEwMCwKV2lsbCBEZWFjb24gPHdpbGxAa2Vy bmVsLm9yZz4gd3JvdGU6Cj4gCj4gT24gVGh1LCBBdWcgMTIsIDIwMjEgYXQgMDg6MDI6MTFQTSAr MDEwMCwgTWFyYyBaeW5naWVyIHdyb3RlOgo+ID4gSGF2aW5nIEhWQyBkaXNhYmxlZCBmcm9tIEVM MyB3aGlsZSB0aGUga2VybmVsIGlzIGVudGVyZWQgYXQgRUwyCj4gPiBpcyBhIGNvbXBsZXRlIG5p Z2h0bWFyZS4KPiA+IAo+ID4gV2UgZW5kLXVwIHRha2luZyBhbiBVTkRFRiBhdCB0aGUgd29yc2Ug cG9zc2libGUgbW9tZW50IChjaGVja2luZwo+ID4gZm9yIFZIRSkgYW5kIGV2ZW4gaWYgd2UgZGlk bid0LCBoYXZpbmcgS1ZNIGVuYWJsZWQgd291bGQgc2lnbmlmeQo+ID4gdGhlIHByZW1hdHVyZSBl bmQgb2YgdGhlIGtlcm5lbC4KPiA+IAo+ID4gSW5zdGVhZCwgdHJ5IGFuZCBkZXRlY3QgdGhpcyBz dHVwaWQgY2FzZSBieSBpc3N1aW5nIGEgSFZDCj4gPiBmb3IgSFZDX1JFU0VUX1ZFQ1RPUlMsIHdo aWNoIGRvZXMgbm90aGluZyB3aGVuIHRoZSBzdHVicwo+ID4gYXJlIGxpdmUuIElmIHdlIGdldCBI VkNfU1RVQl9FUlIgYmFjaywgdGhhdCdzIGJlY2F1c2UgdGhlCj4gPiBVTkRFRiBoYW5kbGVyIGhh cyBraWNrZWQgaW4uCj4gPiAKPiA+IEluIHRoaXMgc2l0dWF0aW9uLCBjbG9zZSB5b3VyIGV5ZXMs IGJsb2NrIHlvdXIgbm9zZSwgYW5kIGdyYWNlZnVsbHkKPiA+IHByZXRlbmQgd2UgaGF2ZSBib290 ZWQgYXQgRUwxLgo+ID4gCj4gPiBSZXBvcnRlZC1ieTogUmFmYcWCIE1pxYJlY2tpIDx6YWplYzVA Z21haWwuY29tPgo+ID4gU2lnbmVkLW9mZi1ieTogTWFyYyBaeW5naWVyIDxtYXpAa2VybmVsLm9y Zz4KPiA+IC0tLQo+ID4gIGFyY2gvYXJtNjQva2VybmVsL2hlYWQuUyB8IDIyICsrKysrKysrKysr KysrKysrKysrKysKPiA+ICAxIGZpbGUgY2hhbmdlZCwgMjIgaW5zZXJ0aW9ucygrKQo+ID4gCj4g PiBkaWZmIC0tZ2l0IGEvYXJjaC9hcm02NC9rZXJuZWwvaGVhZC5TIGIvYXJjaC9hcm02NC9rZXJu ZWwvaGVhZC5TCj4gPiBpbmRleCA5ZDVhYTU2YTk4Y2MuLmQ2YjJiMDVmNWQzYSAxMDA2NDQKPiA+ IC0tLSBhL2FyY2gvYXJtNjQva2VybmVsL2hlYWQuUwo+ID4gKysrIGIvYXJjaC9hcm02NC9rZXJu ZWwvaGVhZC5TCj4gPiBAQCAtNTE5LDYgKzUxOSwyOCBAQCBTWU1fSU5ORVJfTEFCRUwoaW5pdF9l bDIsIFNZTV9MX0xPQ0FMKQo+ID4gIAltc3IJdmJhcl9lbDIsIHgwCj4gPiAgCWlzYgo+ID4gIAo+ ID4gKwkvLyBDaGVjayB0aGF0IEhWQyBhY3R1YWxseSB3b3Jrcy4uLgo+ID4gKwltb3YJeDAsICNI VkNfUkVTRVRfVkVDVE9SUwo+ID4gKwlodmMJIzAKPiA+ICsKPiA+ICsJbW92X3EJeDEsIEhWQ19T VFVCX0VSUgo+ID4gKwljbXAJeDAsIHgxCj4gPiArCWIubmUJMGYKPiA+ICsKPiA+ICsJLyoKPiA+ ICsJICogSFZDIGlzIHVudXNhYmxlLCBzbyBwcmV0ZW5kIHdlIGFjdHVhbGx5IGJvb3RlZCBhdCBF TDEuCj4gPiArCSAqIE9uY2Ugd2UgaGF2ZSBsZWZ0IEVMMiwgdGhlcmUgd2lsbCBiZSBubyBnb2lu ZyBiYWNrLgo+ID4gKwkgKi8KPiAKPiBUaGlzIGNvbW1lbnQgZ290IG1lIHRoaW5raW5nLi4uCj4g Cj4gCS5tYWNybwlob3N0X2h2YzAKPiAJbXJzCXh6ciwgYWN0bHJfZWwxCj4gCS5lbmRtCj4gCj4g dGhlbiBzZXQgSENSX0VMMi5UQUNSPTEgd2hpbGUgd2Ugc3RpbGwgY2FuIGFuZCBtYXRjaCB0aGUg SVNTIGFnYWluc3QgYQo+IGNvbnN0YW50IGluIHRoZSBoYW5kbGVyLiBUb28gYXdmdWw/CgpJIGhh ZCBhIHNpbWlsYXIgaWRlYSwgdXNpbmcgYW4gSUQgcmVnaXN0ZXIgaW5zdGVhZCAodGhvdWdoIEFD VExSX0VMMQppcyBtdWNoIG5lYXRlcikuIEl0IHdvdWxkIGluZGVlZCBhbGxvdyB0aGUga2VybmVs IHRvIGdvIGJhY2sgdG8gRUwyLgoKQnV0IGZvciB3aGF0IHB1cnBvc2U/IFllcywgd2UgY291bGQg ZW5hYmxlIEtWTSB0aGF0IHdheS4gSG93ZXZlciwgdGhlCmd1ZXN0IHdvdWxkIG5lZWQgdG8ga25v dyBhYm91dCBpdCBhcyB3ZWxsLCBhcyBldmVuIHNpbXBsZSB0aGluZ3MgbGlrZQpQU0NJIHdvdWxk bid0IHdvcmsuIFRoYXQncyB3b3VsZCBiZSBkZWZpbmluZyBhIG5ldyBndWVzdCBBQkksIGFuZCBJ J20Kbm90IG92ZXJseSBrZWVuIG9uIGl0LgoKVW5sZXNzIHlvdSBhcmUgdGhpbmtpbmcgb2Ygc29t ZXRoaW5nIGVsc2U/CgpUaGFua3MsCgoJTS4KCi0tIApXaXRob3V0IGRldmlhdGlvbiBmcm9tIHRo ZSBub3JtLCBwcm9ncmVzcyBpcyBub3QgcG9zc2libGUuCgpfX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fXwpsaW51eC1hcm0ta2VybmVsIG1haWxpbmcgbGlzdAps aW51eC1hcm0ta2VybmVsQGxpc3RzLmluZnJhZGVhZC5vcmcKaHR0cDovL2xpc3RzLmluZnJhZGVh ZC5vcmcvbWFpbG1hbi9saXN0aW5mby9saW51eC1hcm0ta2VybmVsCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E632C4338F for ; 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Fri, 13 Aug 2021 18:33:50 +0100 Date: Fri, 13 Aug 2021 18:33:58 +0100 Message-ID: <87k0kp1c6x.wl-maz@kernel.org> From: Marc Zyngier To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Florian Fainelli , bcm-kernel-feedback-list@broadcom.com, kernel-team@android.com Subject: Re: [PATCH 3/5] arm64: Detect disabled HVC early In-Reply-To: <20210813090539.GA7536@willie-the-truck> References: <20210812190213.2601506-1-maz@kernel.org> <20210812190213.2601506-4-maz@kernel.org> <20210813090539.GA7536@willie-the-truck> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-SA-Exim-Connect-IP: 109.170.232.56 X-SA-Exim-Rcpt-To: will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, zajec5@gmail.com, catalin.marinas@arm.com, mark.rutland@arm.com, ardb@kernel.org, f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 13 Aug 2021 10:05:40 +0100, Will Deacon wrote: > > On Thu, Aug 12, 2021 at 08:02:11PM +0100, Marc Zyngier wrote: > > Having HVC disabled from EL3 while the kernel is entered at EL2 > > is a complete nightmare. > > > > We end-up taking an UNDEF at the worse possible moment (checking > > for VHE) and even if we didn't, having KVM enabled would signify > > the premature end of the kernel. > > > > Instead, try and detect this stupid case by issuing a HVC > > for HVC_RESET_VECTORS, which does nothing when the stubs > > are live. If we get HVC_STUB_ERR back, that's because the > > UNDEF handler has kicked in. > > > > In this situation, close your eyes, block your nose, and gracefully > > pretend we have booted at EL1. > > > > Reported-by: Rafał Miłecki > > Signed-off-by: Marc Zyngier > > --- > > arch/arm64/kernel/head.S | 22 ++++++++++++++++++++++ > > 1 file changed, 22 insertions(+) > > > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > > index 9d5aa56a98cc..d6b2b05f5d3a 100644 > > --- a/arch/arm64/kernel/head.S > > +++ b/arch/arm64/kernel/head.S > > @@ -519,6 +519,28 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL) > > msr vbar_el2, x0 > > isb > > > > + // Check that HVC actually works... > > + mov x0, #HVC_RESET_VECTORS > > + hvc #0 > > + > > + mov_q x1, HVC_STUB_ERR > > + cmp x0, x1 > > + b.ne 0f > > + > > + /* > > + * HVC is unusable, so pretend we actually booted at EL1. > > + * Once we have left EL2, there will be no going back. > > + */ > > This comment got me thinking... > > .macro host_hvc0 > mrs xzr, actlr_el1 > .endm > > then set HCR_EL2.TACR=1 while we still can and match the ISS against a > constant in the handler. Too awful? I had a similar idea, using an ID register instead (though ACTLR_EL1 is much neater). It would indeed allow the kernel to go back to EL2. But for what purpose? Yes, we could enable KVM that way. However, the guest would need to know about it as well, as even simple things like PSCI wouldn't work. That's would be defining a new guest ABI, and I'm not overly keen on it. Unless you are thinking of something else? Thanks, M. -- Without deviation from the norm, progress is not possible.