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spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Subject:To:From: Message-ID:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=EcYAR4yeub6RGF1v5sTH1MTDEz1TwKrJmn43D2kH3VM=; b=OVEWVk/Z+zIEaOHpNaZaqeWfr b9IW/dmK5pigV4XFfZD1LpNppuytg+Hwe9+9H94ez3SpofyhaM97bLJdn75597vemA/Lx5I56NrN3 PsD0uvNYfBmw6YS2ylFemZjAiJHw0CpPrzOzByJr8ZhICfTscS/T/0IBYar+NPhfDTN3wlYP5xywj GJtMWyNn9W0mTyNWyXrNJ9xxtzSpLpxUeynMvb9oyOyg+DGLgydM2VvR3LS14eLOruwGA6XxvjyRG r1u5tKsmvb0LMswOlMsepP7UgZH5be1djtC2d95mQZY/7BURopYF5oT88t+45D4qaawcY+l3c/UZi qLpHQnw4g==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l3kN0-0007yh-DT; Sun, 24 Jan 2021 18:44:18 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l3kMx-0007yF-T3 for linux-arm-kernel@lists.infradead.org; Sun, 24 Jan 2021 18:44:16 +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 E98CE222BB; Sun, 24 Jan 2021 18:44:14 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] 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) (envelope-from ) id 1l3kMu-009lbm-U9; Sun, 24 Jan 2021 18:44:13 +0000 Date: Sun, 24 Jan 2021 18:44:11 +0000 Message-ID: <87sg6qjhtw.wl-maz@kernel.org> From: Marc Zyngier To: David Brazdil Subject: Re: [PATCH v4 04/21] arm64: Provide an 'upgrade to VHE' stub hypercall In-Reply-To: <20210118112516.6a7lnrtbjvey4iiv@google.com> References: <20210118094533.2874082-1-maz@kernel.org> <20210118094533.2874082-5-maz@kernel.org> <20210118112516.6a7lnrtbjvey4iiv@google.com> 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: 62.31.163.78 X-SA-Exim-Rcpt-To: dbrazdil@google.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, alexandru.elisei@arm.com, ardb@kernel.org, jingzhangos@google.com, pajay@qti.qualcomm.com, psodagud@codeaurora.org, sramana@codeaurora.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.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-20210124_134416_059680_B045B645 X-CRM114-Status: GOOD ( 29.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Jing Zhang , kernel-team@android.com, Srinivas Ramana , Suzuki K Poulose , Catalin Marinas , Alexandru Elisei , linux-kernel@vger.kernel.org, Ard Biesheuvel , James Morse , Julien Thierry , Ajay Patil , Prasad Sodagudi , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 18 Jan 2021 11:25:16 +0000, David Brazdil wrote: > > On Mon, Jan 18, 2021 at 09:45:16AM +0000, Marc Zyngier wrote: > > As we are about to change the way a VHE system boots, let's > > provide the core helper, in the form of a stub hypercall that > > enables VHE and replicates the full EL1 context at EL2, thanks > > to EL1 and VHE-EL2 being extremely similar. > > > > On exception return, the kernel carries on at EL2. Fancy! > > > > Nothing calls this new hypercall yet, so no functional change. > > > > Signed-off-by: Marc Zyngier > > --- > > arch/arm64/include/asm/virt.h | 7 +++- > > arch/arm64/kernel/hyp-stub.S | 67 +++++++++++++++++++++++++++++++++-- > > 2 files changed, 71 insertions(+), 3 deletions(-) > > > > diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h > > index ee6a48df89d9..7379f35ae2c6 100644 > > --- a/arch/arm64/include/asm/virt.h > > +++ b/arch/arm64/include/asm/virt.h > > @@ -35,8 +35,13 @@ > > */ > > #define HVC_RESET_VECTORS 2 > > > > +/* > > + * HVC_VHE_RESTART - Upgrade the CPU from EL1 to EL2, if possible > > + */ > > +#define HVC_VHE_RESTART 3 > > + > > /* Max number of HYP stub hypercalls */ > > -#define HVC_STUB_HCALL_NR 3 > > +#define HVC_STUB_HCALL_NR 4 > > > > /* Error returned when an invalid stub number is passed into x0 */ > > #define HVC_STUB_ERR 0xbadca11 > > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S > > index 160f5881a0b7..fb12398b5c28 100644 > > --- a/arch/arm64/kernel/hyp-stub.S > > +++ b/arch/arm64/kernel/hyp-stub.S > > @@ -8,9 +8,9 @@ > > > > #include > > #include > > -#include > > > > #include > > +#include > > #include > > #include > > #include > > @@ -47,10 +47,13 @@ SYM_CODE_END(__hyp_stub_vectors) > > > > SYM_CODE_START_LOCAL(el1_sync) > > cmp x0, #HVC_SET_VECTORS > > - b.ne 2f > > + b.ne 1f > > msr vbar_el2, x1 > > b 9f > > > > +1: cmp x0, #HVC_VHE_RESTART > > + b.eq mutate_to_vhe > > + > > 2: cmp x0, #HVC_SOFT_RESTART > > b.ne 3f > > mov x0, x2 > > @@ -70,6 +73,66 @@ SYM_CODE_START_LOCAL(el1_sync) > > eret > > SYM_CODE_END(el1_sync) > > > > +// nVHE? No way! Give me the real thing! > > +SYM_CODE_START_LOCAL(mutate_to_vhe) > > + // Sanity check: MMU *must* be off > > + mrs x0, sctlr_el2 > > + tbnz x0, #0, 1f > > + > > + // Needs to be VHE capable, obviously > > + mrs x0, id_aa64mmfr1_el1 > > + ubfx x0, x0, #ID_AA64MMFR1_VHE_SHIFT, #4 > > + cbz x0, 1f > > nit: There is a HVC_STUB_ERR that you could return if these sanity > checks fail. The documentation also states that it should be > returned on error. Good point. I've now added it, but how the error can be handled is still up in the air. For now, I've decided to let the kernel continue its (probably doomed) course. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel