From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Upton Date: Wed, 22 May 2024 08:16:07 -0700 Subject: [PATCH v2 1/6] KVM: Add a flag to track if a loaded vCPU is scheduled out In-Reply-To: <20240522014013.1672962-2-seanjc@google.com> References: <20240522014013.1672962-1-seanjc@google.com> <20240522014013.1672962-2-seanjc@google.com> Message-ID: List-Id: To: kvm-riscv@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Tue, May 21, 2024 at 06:40:08PM -0700, Sean Christopherson wrote: > Add a kvm_vcpu.scheduled_out flag to track if a vCPU is in the process of > being scheduled out (vCPU put path), or if the vCPU is being reloaded > after being scheduled out (vCPU load path). In the short term, this will > allow dropping kvm_arch_sched_in(), as arch code can query scheduled_out > during kvm_arch_vcpu_load(). > > Longer term, scheduled_out opens up other potential optimizations, without > creating subtle/brittle dependencies. E.g. it allows KVM to keep guest > state (that is managed via kvm_arch_vcpu_{load,put}()) loaded across > kvm_sched_{out,in}(), if KVM knows the state isn't accessed by the host > kernel. Forcing arch code to coordinate between kvm_arch_sched_{in,out}() > and kvm_arch_vcpu_{load,put}() is awkward, not reusable, and relies on the > exact ordering of calls into arch code. > > Adding scheduled_out also obviates the need for a kvm_arch_sched_out() > hook, e.g. if arch code needs to do something novel when putting vCPU > state. > > And even if KVM never uses scheduled_out for anything beyond dropping > kvm_arch_sched_in(), just being able to remove all of the arch stubs makes > it worth adding the flag. > > Link: https://lore.kernel.org/all/20240430224431.490139-1-seanjc at google.com > Cc: Oliver Upton > Signed-off-by: Sean Christopherson Reviewed-by: Oliver Upton -- Thanks, Oliver From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta1.migadu.com (out-186.mta1.migadu.com [95.215.58.186]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D20B91B815 for ; Wed, 22 May 2024 15:16:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716390982; cv=none; b=uKNnBWec9xHE8DuN1U2T2j4luaH7XET/eA9bRjd2vTkiTz7llPQ6ef+Hb+Rb6JwGGutZ3jIROu6GgimEItk7KYG9DsDnMlnrf4R/s6JVwSw/8rLT+pVNpl2OH6aoz9YNAgKq8RTJFNG2ue8qrat3y+fg+/f5ACGkcuE1lySP+tQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716390982; c=relaxed/simple; bh=LBsuxRIt25iSTct1CaOFF4pb8q9+nLplzWcPNkULdk8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=p5YhSkKWqejiee7ekEq0w6WzHFDzfu3lzmJKx11i1PMD9gzUzIslBqv2onzQ7A7gB/842jXc0Jrib0LSDUMWv1ABPeZLJLENWGpikZtIWQ4n/QB05S6Gie5oO66LG1qYEREiTU93ei6MGy9usbrgdt9/zP2b2cMmXgTVc/eZ+Hc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=MR8HfGt/; arc=none smtp.client-ip=95.215.58.186 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="MR8HfGt/" X-Envelope-To: seanjc@google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1716390977; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qPx5VBeAtVusPub5h8jjoS2Zp/k7LiSDo3T23EUz3Cc=; b=MR8HfGt/7NWj1OeZKFuwxnVF9+ndS7xCoaOY+r1JI2bWBzf2MynLiEMDjC1DrcozAH8hei TUnFiYL5Pyj+E10/+shwWi4h/9LVvu0Mc6mkr1yRH6n++3msAFiuDQVzo86zkrGkaVb0hH 6NbyKC1AGLafKPP8z0hv7d6a9IuqBaQ= X-Envelope-To: maz@kernel.org X-Envelope-To: zhaotianrui@loongson.cn X-Envelope-To: maobibo@loongson.cn X-Envelope-To: chenhuacai@kernel.org X-Envelope-To: mpe@ellerman.id.au X-Envelope-To: anup@brainfault.org X-Envelope-To: paul.walmsley@sifive.com X-Envelope-To: palmer@dabbelt.com X-Envelope-To: aou@eecs.berkeley.edu X-Envelope-To: borntraeger@linux.ibm.com X-Envelope-To: frankja@linux.ibm.com X-Envelope-To: imbrenda@linux.ibm.com X-Envelope-To: pbonzini@redhat.com X-Envelope-To: linux-arm-kernel@lists.infradead.org X-Envelope-To: kvmarm@lists.linux.dev X-Envelope-To: kvm@vger.kernel.org X-Envelope-To: loongarch@lists.linux.dev X-Envelope-To: linux-mips@vger.kernel.org X-Envelope-To: linuxppc-dev@lists.ozlabs.org X-Envelope-To: kvm-riscv@lists.infradead.org X-Envelope-To: linux-riscv@lists.infradead.org X-Envelope-To: linux-kernel@vger.kernel.org Date: Wed, 22 May 2024 08:16:07 -0700 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Sean Christopherson Cc: Marc Zyngier , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Paolo Bonzini , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/6] KVM: Add a flag to track if a loaded vCPU is scheduled out Message-ID: References: <20240522014013.1672962-1-seanjc@google.com> <20240522014013.1672962-2-seanjc@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240522014013.1672962-2-seanjc@google.com> X-Migadu-Flow: FLOW_OUT On Tue, May 21, 2024 at 06:40:08PM -0700, Sean Christopherson wrote: > Add a kvm_vcpu.scheduled_out flag to track if a vCPU is in the process of > being scheduled out (vCPU put path), or if the vCPU is being reloaded > after being scheduled out (vCPU load path). In the short term, this will > allow dropping kvm_arch_sched_in(), as arch code can query scheduled_out > during kvm_arch_vcpu_load(). > > Longer term, scheduled_out opens up other potential optimizations, without > creating subtle/brittle dependencies. E.g. it allows KVM to keep guest > state (that is managed via kvm_arch_vcpu_{load,put}()) loaded across > kvm_sched_{out,in}(), if KVM knows the state isn't accessed by the host > kernel. Forcing arch code to coordinate between kvm_arch_sched_{in,out}() > and kvm_arch_vcpu_{load,put}() is awkward, not reusable, and relies on the > exact ordering of calls into arch code. > > Adding scheduled_out also obviates the need for a kvm_arch_sched_out() > hook, e.g. if arch code needs to do something novel when putting vCPU > state. > > And even if KVM never uses scheduled_out for anything beyond dropping > kvm_arch_sched_in(), just being able to remove all of the arch stubs makes > it worth adding the flag. > > Link: https://lore.kernel.org/all/20240430224431.490139-1-seanjc@google.com > Cc: Oliver Upton > Signed-off-by: Sean Christopherson Reviewed-by: Oliver Upton -- Thanks, Oliver 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 5A42DC25B7D for ; Wed, 22 May 2024 15:16:40 +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=Q1ZEK0LN77UqINJdBJpropHVFBbBdX9F97n5fsAhI48=; b=S7vdkxyduG97mX Mt/aMRK+EHTs/pXCgvaQC/M4P5/2v8RN7qkCB+yr5VuXhzwPHmxkx1N2JbD1rcbFo+/fuBhRLtZSN c3RA/3JFo5MFGtVP4KW7fvzgSOlb8SBbQdPm3ZVCKbKCrtFBfwlbST0ybstObaw4RqCxr15dSmdy9 MvqsN682uZzoiGe1gVrRvTZo0VLEmB336pV2BTvAOOuCNaw5MoOs07XwVBcIY1TT0jGxXt7PEqIBs yabzWRjtXA3xM7hof7XKpxUuPM0Jw59+U6caXxJBKZt9lQkDEkia2hQWMYz9ZWKTlci7mVI9J4nUs 6bbWOtfZRizHOc1S85Fg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9nha-00000003Ko0-1Y9a; Wed, 22 May 2024 15:16:26 +0000 Received: from out-182.mta1.migadu.com ([2001:41d0:203:375::b6]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9nhW-00000003KmB-25uy for linux-riscv@lists.infradead.org; Wed, 22 May 2024 15:16:25 +0000 X-Envelope-To: seanjc@google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1716390977; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qPx5VBeAtVusPub5h8jjoS2Zp/k7LiSDo3T23EUz3Cc=; b=MR8HfGt/7NWj1OeZKFuwxnVF9+ndS7xCoaOY+r1JI2bWBzf2MynLiEMDjC1DrcozAH8hei TUnFiYL5Pyj+E10/+shwWi4h/9LVvu0Mc6mkr1yRH6n++3msAFiuDQVzo86zkrGkaVb0hH 6NbyKC1AGLafKPP8z0hv7d6a9IuqBaQ= X-Envelope-To: maz@kernel.org X-Envelope-To: zhaotianrui@loongson.cn X-Envelope-To: maobibo@loongson.cn X-Envelope-To: chenhuacai@kernel.org X-Envelope-To: mpe@ellerman.id.au X-Envelope-To: anup@brainfault.org X-Envelope-To: paul.walmsley@sifive.com X-Envelope-To: palmer@dabbelt.com X-Envelope-To: aou@eecs.berkeley.edu X-Envelope-To: borntraeger@linux.ibm.com X-Envelope-To: frankja@linux.ibm.com X-Envelope-To: imbrenda@linux.ibm.com X-Envelope-To: pbonzini@redhat.com X-Envelope-To: linux-arm-kernel@lists.infradead.org X-Envelope-To: kvmarm@lists.linux.dev X-Envelope-To: kvm@vger.kernel.org X-Envelope-To: loongarch@lists.linux.dev X-Envelope-To: linux-mips@vger.kernel.org X-Envelope-To: linuxppc-dev@lists.ozlabs.org X-Envelope-To: kvm-riscv@lists.infradead.org X-Envelope-To: linux-riscv@lists.infradead.org X-Envelope-To: linux-kernel@vger.kernel.org Date: Wed, 22 May 2024 08:16:07 -0700 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Sean Christopherson Cc: Marc Zyngier , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Paolo Bonzini , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/6] KVM: Add a flag to track if a loaded vCPU is scheduled out Message-ID: References: <20240522014013.1672962-1-seanjc@google.com> <20240522014013.1672962-2-seanjc@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240522014013.1672962-2-seanjc@google.com> X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240522_081622_701548_7131190F X-CRM114-Status: GOOD ( 14.40 ) X-BeenThere: linux-riscv@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="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Tue, May 21, 2024 at 06:40:08PM -0700, Sean Christopherson wrote: > Add a kvm_vcpu.scheduled_out flag to track if a vCPU is in the process of > being scheduled out (vCPU put path), or if the vCPU is being reloaded > after being scheduled out (vCPU load path). In the short term, this will > allow dropping kvm_arch_sched_in(), as arch code can query scheduled_out > during kvm_arch_vcpu_load(). > > Longer term, scheduled_out opens up other potential optimizations, without > creating subtle/brittle dependencies. E.g. it allows KVM to keep guest > state (that is managed via kvm_arch_vcpu_{load,put}()) loaded across > kvm_sched_{out,in}(), if KVM knows the state isn't accessed by the host > kernel. Forcing arch code to coordinate between kvm_arch_sched_{in,out}() > and kvm_arch_vcpu_{load,put}() is awkward, not reusable, and relies on the > exact ordering of calls into arch code. > > Adding scheduled_out also obviates the need for a kvm_arch_sched_out() > hook, e.g. if arch code needs to do something novel when putting vCPU > state. > > And even if KVM never uses scheduled_out for anything beyond dropping > kvm_arch_sched_in(), just being able to remove all of the arch stubs makes > it worth adding the flag. > > Link: https://lore.kernel.org/all/20240430224431.490139-1-seanjc@google.com > Cc: Oliver Upton > Signed-off-by: Sean Christopherson Reviewed-by: Oliver Upton -- Thanks, Oliver _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5B9B1C25B78 for ; Wed, 22 May 2024 15:26:36 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=MR8HfGt/; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Vkw0S06fjz78gh for ; Thu, 23 May 2024 01:17:44 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=MR8HfGt/; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.dev (client-ip=95.215.58.175; helo=out-175.mta1.migadu.com; envelope-from=oliver.upton@linux.dev; receiver=lists.ozlabs.org) Received: from out-175.mta1.migadu.com (out-175.mta1.migadu.com [95.215.58.175]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4VkvzZ3M4kz3g8v for ; Thu, 23 May 2024 01:16:58 +1000 (AEST) X-Envelope-To: seanjc@google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1716390977; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qPx5VBeAtVusPub5h8jjoS2Zp/k7LiSDo3T23EUz3Cc=; b=MR8HfGt/7NWj1OeZKFuwxnVF9+ndS7xCoaOY+r1JI2bWBzf2MynLiEMDjC1DrcozAH8hei TUnFiYL5Pyj+E10/+shwWi4h/9LVvu0Mc6mkr1yRH6n++3msAFiuDQVzo86zkrGkaVb0hH 6NbyKC1AGLafKPP8z0hv7d6a9IuqBaQ= X-Envelope-To: maz@kernel.org X-Envelope-To: zhaotianrui@loongson.cn X-Envelope-To: maobibo@loongson.cn X-Envelope-To: chenhuacai@kernel.org X-Envelope-To: mpe@ellerman.id.au X-Envelope-To: anup@brainfault.org X-Envelope-To: paul.walmsley@sifive.com X-Envelope-To: palmer@dabbelt.com X-Envelope-To: aou@eecs.berkeley.edu X-Envelope-To: borntraeger@linux.ibm.com X-Envelope-To: frankja@linux.ibm.com X-Envelope-To: imbrenda@linux.ibm.com X-Envelope-To: pbonzini@redhat.com X-Envelope-To: linux-arm-kernel@lists.infradead.org X-Envelope-To: kvmarm@lists.linux.dev X-Envelope-To: kvm@vger.kernel.org X-Envelope-To: loongarch@lists.linux.dev X-Envelope-To: linux-mips@vger.kernel.org X-Envelope-To: linuxppc-dev@lists.ozlabs.org X-Envelope-To: kvm-riscv@lists.infradead.org X-Envelope-To: linux-riscv@lists.infradead.org X-Envelope-To: linux-kernel@vger.kernel.org Date: Wed, 22 May 2024 08:16:07 -0700 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Sean Christopherson Subject: Re: [PATCH v2 1/6] KVM: Add a flag to track if a loaded vCPU is scheduled out Message-ID: References: <20240522014013.1672962-1-seanjc@google.com> <20240522014013.1672962-2-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240522014013.1672962-2-seanjc@google.com> X-Migadu-Flow: FLOW_OUT X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Claudio Imbrenda , Janosch Frank , Marc Zyngier , Huacai Chen , Christian Borntraeger , Albert Ou , Bibo Mao , loongarch@lists.linux.dev, Paul Walmsley , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, Anup Patel , linux-mips@vger.kernel.org, Palmer Dabbelt , kvm-riscv@lists.infradead.org, Paolo Bonzini , Tianrui Zhao , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, May 21, 2024 at 06:40:08PM -0700, Sean Christopherson wrote: > Add a kvm_vcpu.scheduled_out flag to track if a vCPU is in the process of > being scheduled out (vCPU put path), or if the vCPU is being reloaded > after being scheduled out (vCPU load path). In the short term, this will > allow dropping kvm_arch_sched_in(), as arch code can query scheduled_out > during kvm_arch_vcpu_load(). > > Longer term, scheduled_out opens up other potential optimizations, without > creating subtle/brittle dependencies. E.g. it allows KVM to keep guest > state (that is managed via kvm_arch_vcpu_{load,put}()) loaded across > kvm_sched_{out,in}(), if KVM knows the state isn't accessed by the host > kernel. Forcing arch code to coordinate between kvm_arch_sched_{in,out}() > and kvm_arch_vcpu_{load,put}() is awkward, not reusable, and relies on the > exact ordering of calls into arch code. > > Adding scheduled_out also obviates the need for a kvm_arch_sched_out() > hook, e.g. if arch code needs to do something novel when putting vCPU > state. > > And even if KVM never uses scheduled_out for anything beyond dropping > kvm_arch_sched_in(), just being able to remove all of the arch stubs makes > it worth adding the flag. > > Link: https://lore.kernel.org/all/20240430224431.490139-1-seanjc@google.com > Cc: Oliver Upton > Signed-off-by: Sean Christopherson Reviewed-by: Oliver Upton -- Thanks, Oliver 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 8DCF3C25B78 for ; Wed, 22 May 2024 15:16:38 +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=LYXhzkV4CBt+oNOEUov0qUVs9hWLH4Q7D5idaHYa35Y=; b=y3r/I3xV0pg4rP +40l4VwkMl3PPC5p5eLFR/va0b2sGEJoaNg9DdW+8PI6HbPOhW502aISkM+RAoGg0/ttpU4K2VTWl zLQ1CwqbVJcDWPtMBNaa4nDsXcGgSgfaIvHmELJjPxFUh/snvBMHCmpFJ53htOdtrqsjVIZjcdLfR En+JL33AN0boCBAQ4HwLBpkMtvVPkwTL0s479uCjhm8QUsCMj+F7YocOkKGlGxRa93UMopfc4hzkH CLnDml82LHH29EML0n5RGD+w398B9mXzdMT6YXLI6kGVIcJee6mDpV0GgmIJ2pvILCYGgkpeMT57W g/MKl89Zivp+vUdcpRrQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9nhY-00000003KnT-3aUE; Wed, 22 May 2024 15:16:24 +0000 Received: from out-177.mta1.migadu.com ([95.215.58.177]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9nhV-00000003Km6-3ZVM for linux-arm-kernel@lists.infradead.org; Wed, 22 May 2024 15:16:23 +0000 X-Envelope-To: seanjc@google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1716390977; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qPx5VBeAtVusPub5h8jjoS2Zp/k7LiSDo3T23EUz3Cc=; b=MR8HfGt/7NWj1OeZKFuwxnVF9+ndS7xCoaOY+r1JI2bWBzf2MynLiEMDjC1DrcozAH8hei TUnFiYL5Pyj+E10/+shwWi4h/9LVvu0Mc6mkr1yRH6n++3msAFiuDQVzo86zkrGkaVb0hH 6NbyKC1AGLafKPP8z0hv7d6a9IuqBaQ= X-Envelope-To: maz@kernel.org X-Envelope-To: zhaotianrui@loongson.cn X-Envelope-To: maobibo@loongson.cn X-Envelope-To: chenhuacai@kernel.org X-Envelope-To: mpe@ellerman.id.au X-Envelope-To: anup@brainfault.org X-Envelope-To: paul.walmsley@sifive.com X-Envelope-To: palmer@dabbelt.com X-Envelope-To: aou@eecs.berkeley.edu X-Envelope-To: borntraeger@linux.ibm.com X-Envelope-To: frankja@linux.ibm.com X-Envelope-To: imbrenda@linux.ibm.com X-Envelope-To: pbonzini@redhat.com X-Envelope-To: linux-arm-kernel@lists.infradead.org X-Envelope-To: kvmarm@lists.linux.dev X-Envelope-To: kvm@vger.kernel.org X-Envelope-To: loongarch@lists.linux.dev X-Envelope-To: linux-mips@vger.kernel.org X-Envelope-To: linuxppc-dev@lists.ozlabs.org X-Envelope-To: kvm-riscv@lists.infradead.org X-Envelope-To: linux-riscv@lists.infradead.org X-Envelope-To: linux-kernel@vger.kernel.org Date: Wed, 22 May 2024 08:16:07 -0700 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Sean Christopherson Cc: Marc Zyngier , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Paolo Bonzini , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/6] KVM: Add a flag to track if a loaded vCPU is scheduled out Message-ID: References: <20240522014013.1672962-1-seanjc@google.com> <20240522014013.1672962-2-seanjc@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240522014013.1672962-2-seanjc@google.com> X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240522_081622_267296_3119CF7F X-CRM114-Status: GOOD ( 15.32 ) 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="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 Tue, May 21, 2024 at 06:40:08PM -0700, Sean Christopherson wrote: > Add a kvm_vcpu.scheduled_out flag to track if a vCPU is in the process of > being scheduled out (vCPU put path), or if the vCPU is being reloaded > after being scheduled out (vCPU load path). In the short term, this will > allow dropping kvm_arch_sched_in(), as arch code can query scheduled_out > during kvm_arch_vcpu_load(). > > Longer term, scheduled_out opens up other potential optimizations, without > creating subtle/brittle dependencies. E.g. it allows KVM to keep guest > state (that is managed via kvm_arch_vcpu_{load,put}()) loaded across > kvm_sched_{out,in}(), if KVM knows the state isn't accessed by the host > kernel. Forcing arch code to coordinate between kvm_arch_sched_{in,out}() > and kvm_arch_vcpu_{load,put}() is awkward, not reusable, and relies on the > exact ordering of calls into arch code. > > Adding scheduled_out also obviates the need for a kvm_arch_sched_out() > hook, e.g. if arch code needs to do something novel when putting vCPU > state. > > And even if KVM never uses scheduled_out for anything beyond dropping > kvm_arch_sched_in(), just being able to remove all of the arch stubs makes > it worth adding the flag. > > Link: https://lore.kernel.org/all/20240430224431.490139-1-seanjc@google.com > Cc: Oliver Upton > Signed-off-by: Sean Christopherson Reviewed-by: Oliver Upton -- Thanks, Oliver _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel