From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751507AbeEVPmR (ORCPT ); Tue, 22 May 2018 11:42:17 -0400 Received: from smtp-fw-9101.amazon.com ([207.171.184.25]:56364 "EHLO smtp-fw-9101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751196AbeEVPmQ (ORCPT ); Tue, 22 May 2018 11:42:16 -0400 X-IronPort-AV: E=Sophos;i="5.49,430,1520899200"; d="scan'208";a="742232522" From: "Raslan, KarimAllah" To: "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , "pbonzini@redhat.com" CC: "rkrcmar@redhat.com" Subject: Re: [PATCH] KVM: Switch 'requests' to be 64-bit (explicitly) Thread-Topic: [PATCH] KVM: Switch 'requests' to be 64-bit (explicitly) Thread-Index: AQHT1D++Gdqnz/tFy0K4EdrtXKZQKaQDl3kAgDiG6QA= Date: Tue, 22 May 2018 15:42:08 +0000 Message-ID: <1527003728.13207.55.camel@amazon.de> References: <1523744804-8220-1-git-send-email-karahmed@amazon.de> <53700469-74f0-f3b0-96a4-d8ace2919b36@redhat.com> In-Reply-To: <53700469-74f0-f3b0-96a4-d8ace2919b36@redhat.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.43.165.101] Content-Type: text/plain; charset="utf-8" Content-ID: <7F024E4BA91BD94EAA6E79E996156847@amazon.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id w4MFgN7b011966 On Mon, 2018-04-16 at 18:28 +0200, Paolo Bonzini wrote: > On 15/04/2018 00:26, KarimAllah Ahmed wrote: > > > > Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to > > use the size of "requests" instead of the hard-coded '32'. > > > > That gives us a bit more room again for arch-specific requests as we > > already ran out of space for x86 due to the hard-coded check. > > > > Cc: Paolo Bonzini > > Cc: Radim Krčmář > > Cc: kvm@vger.kernel.org > > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: KarimAllah Ahmed > > I'm afraid architectures like ARM 32 need this to be conditional (using > Kconfig). Why would using a 64-bit 'requests' be a problem for ARM32? Are you  concerned about performance here or is there some symantic problem? > > Thanks, > > Paolo > > > > > --- > > include/linux/kvm_host.h | 10 +++++----- > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 6930c63..fe4f46b 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -129,7 +129,7 @@ static inline bool is_error_page(struct page *page) > > #define KVM_REQUEST_ARCH_BASE 8 > > > > #define KVM_ARCH_REQ_FLAGS(nr, flags) ({ \ > > - BUILD_BUG_ON((unsigned)(nr) >= 32 - KVM_REQUEST_ARCH_BASE); \ > > + BUILD_BUG_ON((unsigned)(nr) >= (sizeof(((struct kvm_vcpu *)0)->requests) * 8) - KVM_REQUEST_ARCH_BASE); \ > > (unsigned)(((nr) + KVM_REQUEST_ARCH_BASE) | (flags)); \ > > }) > > #define KVM_ARCH_REQ(nr) KVM_ARCH_REQ_FLAGS(nr, 0) > > @@ -223,7 +223,7 @@ struct kvm_vcpu { > > int vcpu_id; > > int srcu_idx; > > int mode; > > - unsigned long requests; > > + u64 requests; > > unsigned long guest_debug; > > > > int pre_pcpu; > > @@ -1122,7 +1122,7 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu) > > * caller. Paired with the smp_mb__after_atomic in kvm_check_request. > > */ > > smp_wmb(); > > - set_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > > + set_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > > } > > > > static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) > > @@ -1132,12 +1132,12 @@ static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) > > > > static inline bool kvm_test_request(int req, struct kvm_vcpu *vcpu) > > { > > - return test_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > > + return test_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > > } > > > > static inline void kvm_clear_request(int req, struct kvm_vcpu *vcpu) > > { > > - clear_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > > + clear_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > > } > > > > static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu) > > > > Amazon Development Center Germany GmbH Berlin - Dresden - Aachen main office: Krausenstr. 38, 10117 Berlin Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger Ust-ID: DE289237879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B