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=-9.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 42081C433E2 for ; Sat, 18 Jul 2020 09:00:47 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id AD1F82065D for ; Sat, 18 Jul 2020 09:00:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="GQJjSMq7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD1F82065D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 26D4B4B12E; Sat, 18 Jul 2020 05:00:46 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@kernel.org Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id lC4h8JQWgg7P; Sat, 18 Jul 2020 05:00:44 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B9B494B125; Sat, 18 Jul 2020 05:00:44 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 9F0B14B113 for ; Sat, 18 Jul 2020 05:00:43 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id qwMzYS6nBYnE for ; Sat, 18 Jul 2020 05:00:42 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 584154B109 for ; Sat, 18 Jul 2020 05:00:42 -0400 (EDT) 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 0EE752065D; Sat, 18 Jul 2020 09:00:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595062833; bh=DIxzMhiONY5no3uQC/pQdFmGAw3pRQCnfUTXNpqOtD0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=GQJjSMq7PYMW5HyclQ/YDhHqDtPsLZiHi0DA8FO6m/qLwwrcYKzpN33wQ4ljzMCB0 6OT67tKAt35QYWiEZm8fNIUNaOevidHHBo5x+Ud8ggbaNN3rAYjUEPLi9UNXng2PQd A+Ki/5cO/ZSAqJv+LoHau8bpW3Wx3/sXivx6UMlU= 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:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jwihr-00Cr9t-5K; Sat, 18 Jul 2020 10:00:31 +0100 Date: Sat, 18 Jul 2020 10:00:30 +0100 Message-ID: <87a6zxxknl.wl-maz@kernel.org> From: Marc Zyngier To: Andrew Scull Subject: Re: [PATCH 07/37] KVM: arm64: Separate SError detection from VAXorcism In-Reply-To: <20200715184438.1390996-8-ascull@google.com> References: <20200715184438.1390996-1-ascull@google.com> <20200715184438.1390996-8-ascull@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26.3 (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: ascull@google.com, kvmarm@lists.cs.columbia.edu, james.morse@arm.com, suzuki.poulose@arm.com, julien.thierry.kdev@gmail.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 Cc: kernel-team@android.com, kvmarm@lists.cs.columbia.edu 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Andrew, On Wed, 15 Jul 2020 19:44:08 +0100, Andrew Scull wrote: > > When exiting a guest, just check whether there is an SError pending and > set the bit in the exit code. The fixup then initiates the ceremony > should it be required. > > The separation allows for easier choices to be made as to whether the > demonic consultation should proceed. Such as? > > Signed-off-by: Andrew Scull > --- > arch/arm64/include/asm/kvm_hyp.h | 2 ++ > arch/arm64/kvm/hyp/entry.S | 27 +++++++++++++++++-------- > arch/arm64/kvm/hyp/hyp-entry.S | 1 - > arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ++++ > 4 files changed, 25 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h > index 07745d9c49fc..50a774812761 100644 > --- a/arch/arm64/include/asm/kvm_hyp.h > +++ b/arch/arm64/include/asm/kvm_hyp.h > @@ -91,6 +91,8 @@ void deactivate_traps_vhe_put(void); > > u64 __guest_enter(struct kvm_vcpu *vcpu, struct kvm_cpu_context *host_ctxt); > > +void __vaxorcize_serror(void); I think a VAXorsist reference in the comments is plenty. The code can definitely stay architectural. Something like "__handle_SEI()" should be good. I'm not *that* fun. > + > void __noreturn hyp_panic(struct kvm_cpu_context *host_ctxt); > #ifdef __KVM_NVHE_HYPERVISOR__ > void __noreturn __hyp_do_panic(unsigned long, ...); > diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S > index 6a641fcff4f7..dc4e3e7e7407 100644 > --- a/arch/arm64/kvm/hyp/entry.S > +++ b/arch/arm64/kvm/hyp/entry.S > @@ -174,18 +174,31 @@ alternative_if ARM64_HAS_RAS_EXTN > mrs_s x2, SYS_DISR_EL1 > str x2, [x1, #(VCPU_FAULT_DISR - VCPU_CONTEXT)] > cbz x2, 1f > - msr_s SYS_DISR_EL1, xzr > orr x0, x0, #(1< -1: ret > + nop > +1: > alternative_else > dsb sy // Synchronize against in-flight ld/st > isb // Prevent an early read of side-effect free ISR > mrs x2, isr_el1 > - tbnz x2, #8, 2f // ISR_EL1.A > - ret > - nop > + tbz x2, #8, 2f // ISR_EL1.A > + orr x0, x0, #(1< 2: > alternative_endif > + > + ret > +SYM_FUNC_END(__guest_enter) > + > +/* > + * void __vaxorcize_serror(void); > + */ > +SYM_FUNC_START(__vaxorcize_serror) > + > +alternative_if ARM64_HAS_RAS_EXTN > + msr_s SYS_DISR_EL1, xzr > + ret > +alternative_else_nop_endif > + > // We know we have a pending asynchronous abort, now is the > // time to flush it out. From your VAXorcist book, page 666: > // "Threaten me not, oh Evil one! For I speak with > @@ -193,7 +206,6 @@ alternative_endif > mrs x2, elr_el2 > mrs x3, esr_el2 > mrs x4, spsr_el2 > - mov x5, x0 > > msr daifclr, #4 // Unmask aborts > > @@ -217,6 +229,5 @@ abort_guest_exit_end: > msr elr_el2, x2 > msr esr_el2, x3 > msr spsr_el2, x4 > - orr x0, x0, x5 > 1: ret > -SYM_FUNC_END(__guest_enter) > +SYM_FUNC_END(__vaxorcize_serror) > diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S > index e727bee8e110..c441aabb8ab0 100644 > --- a/arch/arm64/kvm/hyp/hyp-entry.S > +++ b/arch/arm64/kvm/hyp/hyp-entry.S > @@ -177,7 +177,6 @@ el2_error: > adr x1, abort_guest_exit_end > ccmp x0, x1, #4, ne > b.ne __hyp_panic > - mov x0, #(1 << ARM_EXIT_WITH_SERROR_BIT) > eret > sb > > diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h > index 0511af14dc81..14a774d1a35a 100644 > --- a/arch/arm64/kvm/hyp/include/hyp/switch.h > +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h > @@ -405,6 +405,10 @@ static inline bool __hyp_handle_ptrauth(struct kvm_vcpu *vcpu) > */ > static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code) > { > + /* Flush guest SErrors. */ > + if (ARM_SERROR_PENDING(*exit_code)) > + __vaxorcize_serror(); > + > if (ARM_EXCEPTION_CODE(*exit_code) != ARM_EXCEPTION_IRQ) > vcpu->arch.fault.esr_el2 = read_sysreg_el2(SYS_ESR); > > -- > 2.27.0.389.gc38d7665816-goog > > I'm not against this patch, but I wonder whether it actually helps with anything. It spreads the handling across multiple paths, making it harder to read. Could you explain the rational beyond "it's easier"? Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm