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[34.78.232.44]) by smtp.gmail.com with ESMTPSA id b7-20020a5d4b87000000b00314374145e0sm5614126wrt.67.2023.07.04.07.18.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Jul 2023 07:18:13 -0700 (PDT) Date: Tue, 4 Jul 2023 14:18:09 +0000 From: Mostafa Saleh To: Sudeep Holla Cc: maz@kernel.org, oliver.upton@linux.dev, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, tabba@google.com, qperret@google.com, will@kernel.org, catalin.marinas@arm.com, yuzenghui@huawei.com, suzuki.poulose@arm.com, james.morse@arm.com, bgardon@google.com, gshan@redhat.com Subject: Re: [PATCH v3] KVM: arm64: Use BTI for nvhe Message-ID: References: <20230530150845.2856828-1-smostafa@google.com> <20230704134136.a5znw4jupt5yp5kg@bogus> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230704134136.a5znw4jupt5yp5kg@bogus> Hi Sudeep, On Tue, Jul 04, 2023 at 02:41:36PM +0100, Sudeep Holla wrote: > On Tue, May 30, 2023 at 03:08:45PM +0000, Mostafa Saleh wrote: > > CONFIG_ARM64_BTI_KERNEL compiles the kernel to support ARMv8.5-BTI. > > However, the nvhe code doesn't make use of it as it doesn't map any > > pages with Guarded Page(GP) bit. > > > > kvm pgtable code is modified to map executable pages with GP bit > > if BTI is enabled for the kernel. > > > > At hyp init, SCTLR_EL2.BT is set to 1 to match EL1 configuration > > (SCTLR_EL1.BT1) set in bti_enable(). > > > > One difference between kernel and nvhe code, is that the kernel maps > > .text with GP while nvhe maps all the executable pages, this makes > > nvhe code need to deal with special initialization code coming from > > other executable sections (.idmap.text). > > For this we need to add bti instruction at the beginning of > > __kvm_handle_stub_hvc as it can be called by __host_hvc through > > branch instruction(br) and unlike SYM_FUNC_START, SYM_CODE_START > > doesn’t add bti instruction at the beginning, and it can’t be modified > > to add it as it is used with vector tables. > > Another solution which is more intrusive is to convert > > __kvm_handle_stub_hvc to a function and inject “bti jc” instead of > > “bti c” in SYM_FUNC_START > > > > I was chasing a bug in linux-next yesterday with protected nVHE(pKVM) and > cpuidle enabled. The system fails to boot. I just bisected the issue to this > patch and also saw this patch landed in the linus tree yesterday/today. One of the challenges of BTI is that we need to add explicit BTI instructions for assembly code. I checked the code to make sure that nothing was missing, but maybe this is not the case. Can you please share more about the issue (is ESR a Branch Target Exception, call stack...) if possible. Also, is this with CONFIG_ARM_PSCI_CPUIDLE? > Not sure if this is something to do with the fact that pKVM skips to > __kvm_handle_stub_hvc in __host_hvc. __kvm_handle_stub_hvc is called from __host_hvc with "br x5" That's why "bti j" was added at the beginning of __kvm_handle_stub_hvc, so this should be fine. > Let me know if you want be to try something. > > -- > Regards, > Sudeep Thanks, Mostafa 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id DD88BEB64DA for ; Tue, 4 Jul 2023 14:18:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Ng8O7Dk3eeIfbfAEbxwyHTbzDS+W2gNlwRAjx6RUiO0=; b=HtRcUcCodtxYiU CpElu9TnULlBW5aSDkiYPtMTOPcL1+6gtK84NJLLO0xtF/4WgmAw5cKhTau12cqPvkcXaRgvLtrtE O97983aI+NDL6fh+PP0IqOraAbFdRVW2UmnVIkR6gWst874AMgUQdfo0g8cQkDOzS1fQ2UJrMj8Dt rJQ0+LQrxICJ7/cnqxuMcnqLRyHctRIrbPqq2Nk7b1tmz6GDD7Zcd1pmvqhrpllQ5U/qRudcknpwU 0RcnMVmv7P2OkRnROrtZiDDalEqwYn7Koph6kMaeIlVF6hISIV0PcIRJobxUa8328udsohZxaOONi vTx/haSg61o+wJ6BuloA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qGgrF-00DV9w-0v; Tue, 04 Jul 2023 14:18:21 +0000 Received: from mail-wm1-x334.google.com ([2a00:1450:4864:20::334]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qGgrC-00DV8s-0l for linux-arm-kernel@lists.infradead.org; Tue, 04 Jul 2023 14:18:19 +0000 Received: by mail-wm1-x334.google.com with SMTP id 5b1f17b1804b1-3fbd200d354so216695e9.1 for ; Tue, 04 Jul 2023 07:18:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1688480294; x=1691072294; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=eS9MwUiGBcqynGVE0FeA/+dAT/8VCpi0aohdmN5v6Zg=; b=sCUFOvokkesjF48j8RLtdFxTj4gLtePGOpeB71O/AHp13/U4OK6wSukOxneHGZt7QP ugKFzsydFXJeVVKaxyqHd+973UnuqK/GYOSjd18eaYtgHEa+4ZIK2pNzEeGI3STZrX5Q rgA1yHTZpRfUAguLuGAxIVroUfzk8YFU5fz3RmrM13fUum0dmUaUV9wD8cr4GnOs6Ax4 gY1dE52UpgVPUUbVsnjT47zP5rwiD551sDDd75Q/nzwAzeoYXYiBN2KBBHh5nFVcw3MN bfnfr7TyikfppuRMink13/KRQpXdliOKf/vDv/+mVbDejIole33v34f52tGJlWnuyS1F w96A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688480294; x=1691072294; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=eS9MwUiGBcqynGVE0FeA/+dAT/8VCpi0aohdmN5v6Zg=; b=gHLKU/tG7mY2Y4OdDZL+CsJkgKnb66aytxSXqzG5LOI5cFuBEFjMU5i7E2nUWvmkdU xrC0xpm3fW+ncsxbN1UoP+j+3kpk40ya9ozPhVZ8aDHoSIm3jcqLITeUOezi4iMZfmLd i/MG8U9DUtBuqJInqfxK5u9u4foYQFSNxbnvQRR/+yP5M8BdCBdKdhZKzlN4S2bm7YOD MDiG8bJtWlpwk3GG9z9oe+kz5d9dxWjWNLc4uui4b5NQbsk0m7u3BAcX+2MQvcvtsqR7 g3TBuI1ohooh7nkp7FFXAd+srw+uMRQnZ4ONv+nKh7SlQEjpbxuLOYnuGQCFnG8yjqhZ nu3w== X-Gm-Message-State: ABy/qLbCnZFo83vMd3xq+ghdNVFoxV4rjntZInu9/hu023si3ciMRM47 rEO567EGdO0DOvVXkDh93jhP6Q== X-Google-Smtp-Source: APBJJlFy++WqAbmLwJsZUhEhnywQSW5qCv8OEwfmtYtSMRmsV+V5O1kVPJuwdWa99ShJ4T4/oUOPcg== X-Received: by 2002:a05:600c:548d:b0:3f1:70d1:21a6 with SMTP id iv13-20020a05600c548d00b003f170d121a6mr81040wmb.0.1688480293964; Tue, 04 Jul 2023 07:18:13 -0700 (PDT) Received: from google.com (44.232.78.34.bc.googleusercontent.com. [34.78.232.44]) by smtp.gmail.com with ESMTPSA id b7-20020a5d4b87000000b00314374145e0sm5614126wrt.67.2023.07.04.07.18.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Jul 2023 07:18:13 -0700 (PDT) Date: Tue, 4 Jul 2023 14:18:09 +0000 From: Mostafa Saleh To: Sudeep Holla Cc: maz@kernel.org, oliver.upton@linux.dev, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, tabba@google.com, qperret@google.com, will@kernel.org, catalin.marinas@arm.com, yuzenghui@huawei.com, suzuki.poulose@arm.com, james.morse@arm.com, bgardon@google.com, gshan@redhat.com Subject: Re: [PATCH v3] KVM: arm64: Use BTI for nvhe Message-ID: References: <20230530150845.2856828-1-smostafa@google.com> <20230704134136.a5znw4jupt5yp5kg@bogus> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230704134136.a5znw4jupt5yp5kg@bogus> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230704_071818_274994_68F6356A X-CRM114-Status: GOOD ( 31.53 ) 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 SGkgU3VkZWVwLAoKT24gVHVlLCBKdWwgMDQsIDIwMjMgYXQgMDI6NDE6MzZQTSArMDEwMCwgU3Vk ZWVwIEhvbGxhIHdyb3RlOgo+IE9uIFR1ZSwgTWF5IDMwLCAyMDIzIGF0IDAzOjA4OjQ1UE0gKzAw MDAsIE1vc3RhZmEgU2FsZWggd3JvdGU6Cj4gPiBDT05GSUdfQVJNNjRfQlRJX0tFUk5FTCBjb21w aWxlcyB0aGUga2VybmVsIHRvIHN1cHBvcnQgQVJNdjguNS1CVEkuCj4gPiBIb3dldmVyLCB0aGUg bnZoZSBjb2RlIGRvZXNuJ3QgbWFrZSB1c2Ugb2YgaXQgYXMgaXQgZG9lc24ndCBtYXAgYW55Cj4g PiBwYWdlcyB3aXRoIEd1YXJkZWQgUGFnZShHUCkgYml0Lgo+ID4gCj4gPiBrdm0gcGd0YWJsZSBj b2RlIGlzIG1vZGlmaWVkIHRvIG1hcCBleGVjdXRhYmxlIHBhZ2VzIHdpdGggR1AgYml0Cj4gPiBp ZiBCVEkgaXMgZW5hYmxlZCBmb3IgdGhlIGtlcm5lbC4KPiA+IAo+ID4gQXQgaHlwIGluaXQsIFND VExSX0VMMi5CVCBpcyBzZXQgdG8gMSB0byBtYXRjaCBFTDEgY29uZmlndXJhdGlvbgo+ID4gKFND VExSX0VMMS5CVDEpIHNldCBpbiBidGlfZW5hYmxlKCkuCj4gPiAKPiA+IE9uZSBkaWZmZXJlbmNl IGJldHdlZW4ga2VybmVsIGFuZCBudmhlIGNvZGUsIGlzIHRoYXQgdGhlIGtlcm5lbCBtYXBzCj4g PiAudGV4dCB3aXRoIEdQIHdoaWxlIG52aGUgbWFwcyBhbGwgdGhlIGV4ZWN1dGFibGUgcGFnZXMs IHRoaXMgbWFrZXMKPiA+IG52aGUgY29kZSBuZWVkIHRvIGRlYWwgd2l0aCBzcGVjaWFsIGluaXRp YWxpemF0aW9uIGNvZGUgY29taW5nIGZyb20KPiA+IG90aGVyIGV4ZWN1dGFibGUgc2VjdGlvbnMg KC5pZG1hcC50ZXh0KS4KPiA+IEZvciB0aGlzIHdlIG5lZWQgdG8gYWRkIGJ0aSBpbnN0cnVjdGlv biBhdCB0aGUgYmVnaW5uaW5nIG9mCj4gPiBfX2t2bV9oYW5kbGVfc3R1Yl9odmMgYXMgaXQgY2Fu IGJlIGNhbGxlZCBieSAgX19ob3N0X2h2YyB0aHJvdWdoCj4gPiBicmFuY2ggaW5zdHJ1Y3Rpb24o YnIpIGFuZCB1bmxpa2UgU1lNX0ZVTkNfU1RBUlQsIFNZTV9DT0RFX1NUQVJUCj4gPiBkb2VzbuKA mXQgYWRkIGJ0aSBpbnN0cnVjdGlvbiBhdCB0aGUgYmVnaW5uaW5nLCBhbmQgaXQgY2Fu4oCZdCBi ZSBtb2RpZmllZAo+ID4gdG8gYWRkIGl0IGFzIGl0IGlzIHVzZWQgd2l0aCB2ZWN0b3IgdGFibGVz Lgo+ID4gQW5vdGhlciBzb2x1dGlvbiB3aGljaCBpcyBtb3JlIGludHJ1c2l2ZSBpcyB0byBjb252 ZXJ0Cj4gPiBfX2t2bV9oYW5kbGVfc3R1Yl9odmMgdG8gYSBmdW5jdGlvbiBhbmQgaW5qZWN0IOKA nGJ0aSBqY+KAnSBpbnN0ZWFkIG9mCj4gPiDigJxidGkgY+KAnSBpbiBTWU1fRlVOQ19TVEFSVAo+ ID4KPiAKPiBJIHdhcyBjaGFzaW5nIGEgYnVnIGluIGxpbnV4LW5leHQgeWVzdGVyZGF5IHdpdGgg cHJvdGVjdGVkIG5WSEUocEtWTSkgYW5kCj4gY3B1aWRsZSBlbmFibGVkLiBUaGUgc3lzdGVtIGZh aWxzIHRvIGJvb3QuIEkganVzdCBiaXNlY3RlZCB0aGUgaXNzdWUgdG8gdGhpcwo+IHBhdGNoIGFu ZCBhbHNvIHNhdyB0aGlzIHBhdGNoIGxhbmRlZCBpbiB0aGUgbGludXMgdHJlZSB5ZXN0ZXJkYXkv dG9kYXkuCgpPbmUgb2YgdGhlIGNoYWxsZW5nZXMgb2YgQlRJIGlzIHRoYXQgd2UgbmVlZCB0byBh ZGQgZXhwbGljaXQgQlRJIGluc3RydWN0aW9ucwpmb3IgYXNzZW1ibHkgY29kZS4gSSBjaGVja2Vk IHRoZSBjb2RlIHRvIG1ha2Ugc3VyZSB0aGF0IG5vdGhpbmcgd2FzIG1pc3NpbmcsCmJ1dCBtYXli ZSB0aGlzIGlzIG5vdCB0aGUgY2FzZS4KQ2FuIHlvdSBwbGVhc2Ugc2hhcmUgbW9yZSBhYm91dCB0 aGUgaXNzdWUgKGlzIEVTUiBhIEJyYW5jaCBUYXJnZXQgRXhjZXB0aW9uLApjYWxsIHN0YWNrLi4u KSBpZiBwb3NzaWJsZS4KQWxzbywgaXMgdGhpcyB3aXRoIENPTkZJR19BUk1fUFNDSV9DUFVJRExF PwoKPiBOb3Qgc3VyZSBpZiB0aGlzIGlzIHNvbWV0aGluZyB0byBkbyB3aXRoIHRoZSBmYWN0IHRo YXQgcEtWTSBza2lwcyB0bwo+IF9fa3ZtX2hhbmRsZV9zdHViX2h2YyBpbiBfX2hvc3RfaHZjLgpf X2t2bV9oYW5kbGVfc3R1Yl9odmMgaXMgY2FsbGVkIGZyb20gX19ob3N0X2h2YyB3aXRoICJiciB4 NSIKVGhhdCdzIHdoeSAiYnRpIGoiIHdhcyBhZGRlZCBhdCB0aGUgYmVnaW5uaW5nIG9mIF9fa3Zt X2hhbmRsZV9zdHViX2h2YywKc28gdGhpcyBzaG91bGQgYmUgZmluZS4KCj4gTGV0IG1lIGtub3cg aWYgeW91IHdhbnQgYmUgdG8gdHJ5IHNvbWV0aGluZy4KPiAKPiAtLSAKPiBSZWdhcmRzLAo+IFN1 ZGVlcAoKVGhhbmtzLApNb3N0YWZhCgoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX18KbGludXgtYXJtLWtlcm5lbCBtYWlsaW5nIGxpc3QKbGludXgtYXJtLWtl cm5lbEBsaXN0cy5pbmZyYWRlYWQub3JnCmh0dHA6Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxt YW4vbGlzdGluZm8vbGludXgtYXJtLWtlcm5lbAo=