From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Thierry Subject: Re: [PATCH 2/3] arm64: KVM: Allow for direct call of HYP functions when using VHE Date: Wed, 9 Jan 2019 14:52:00 +0000 Message-ID: <84607194-797f-cb82-ff64-f106a447c45a@arm.com> References: <20190109135435.178664-1-marc.zyngier@arm.com> <20190109135435.178664-3-marc.zyngier@arm.com> <20190109142407.GH56789@e119886-lin.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org To: Marc Zyngier , Andrew Murray Return-path: In-Reply-To: Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On 09/01/2019 14:51, Julien Thierry wrote: > > > On 09/01/2019 14:45, Marc Zyngier wrote: >> Hi Andrew, >> >> On 09/01/2019 14:24, Andrew Murray wrote: >>> On Wed, Jan 09, 2019 at 01:54:34PM +0000, Marc Zyngier wrote: >>>> When running VHE, there is no need to jump via some stub to perform >>>> a "HYP" function call, as there is a single address space. >>>> >>>> Let's thus change kvm_call_hyp() and co to perform a direct call >>>> in this case. Although this results in a bit of code expansion, >>>> it allows the compiler to check for type compatibility, something >>>> that we are missing so far. >>>> >>>> Signed-off-by: Marc Zyngier >>>> --- >>>> arch/arm64/include/asm/kvm_host.h | 32 +++++++++++++++++++++++++++++-- >>>> 1 file changed, 30 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >>>> index e54cb7c88a4e..df32edbadd69 100644 >>>> --- a/arch/arm64/include/asm/kvm_host.h >>>> +++ b/arch/arm64/include/asm/kvm_host.h >>>> @@ -370,8 +370,36 @@ void kvm_arm_halt_guest(struct kvm *kvm); >>>> void kvm_arm_resume_guest(struct kvm *kvm); >>>> >>>> u64 __kvm_call_hyp(void *hypfn, ...); >>>> -#define kvm_call_hyp(f, ...) __kvm_call_hyp(kvm_ksym_ref(f), ##__VA_ARGS__) >>>> -#define kvm_call_hyp_ret(f, ...) kvm_call_hyp(f, ##__VA_ARGS__) >>>> + >>>> +/* >>>> + * The couple of isb() below are there to guarantee the same behaviour >>>> + * on VHE as on !VHE, where the eret to EL1 acts as a context >>>> + * synchronization event. >>>> + */ >>>> +#define kvm_call_hyp(f, ...) \ >>>> + do { \ >>>> + if (cpus_have_const_cap(ARM64_HAS_VIRT_HOST_EXTN)) { \ >>>> + f(__VA_ARGS__); \ >>>> + isb(); \ >>>> + } else { \ >>>> + __kvm_call_hyp(kvm_ksym_ref(f), ##__VA_ARGS__); \ >>>> + } \ >>>> + } while(0) >>>> + >>>> +#define kvm_call_hyp_ret(f, ...) \ >>>> + ({ \ >>>> + u64 ret; \ >>>> + \ >>>> + if (cpus_have_const_cap(ARM64_HAS_VIRT_HOST_EXTN)) { \ >>>> + ret = f(__VA_ARGS__); \ >>> >>> __kvm_get_mdcr_el2 and __kvm_vcpu_run_nvhe don't return u64 type, they >>> return a smaller type. I guess any issues would be picked up when compiling, >>> but should the name of the macro be clearer as to the assumptions it makes? >>> Or perhaps take an argument which is the type of ret? >> >> kvm_call_hyp has always returned a u64, so no semantic has changed here. >> >> Otherwise, your suggestion of specifying a return type is interesting, >> but it also gives the programmer another chance to shoot itself in the >> foot by not providing the return type corresponding to the function that >> is called. >> >> Unless we can extract the return type by pure magic, I'm not sure we >> gain much. >> > > Would the following work? > > typeof(f(__VA_ARGS__)) ret; > > If typeof works anything like sizeof, I'd expect it would evaluate stuff it wouldn't* > passed as argument and we'd have the return type of the function. > > Cheers, > -- Julien Thierry 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=-11.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS autolearn=ham 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 36DD9C43387 for ; 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Wed, 9 Jan 2019 06:52:02 -0800 (PST) Subject: Re: [PATCH 2/3] arm64: KVM: Allow for direct call of HYP functions when using VHE From: Julien Thierry To: Marc Zyngier , Andrew Murray References: <20190109135435.178664-1-marc.zyngier@arm.com> <20190109135435.178664-3-marc.zyngier@arm.com> <20190109142407.GH56789@e119886-lin.cambridge.arm.com> Message-ID: <84607194-797f-cb82-ff64-f106a447c45a@arm.com> Date: Wed, 9 Jan 2019 14:52:00 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190109_065203_823055_18E636E2 X-CRM114-Status: GOOD ( 22.51 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 09/01/2019 14:51, Julien Thierry wrote: > > > On 09/01/2019 14:45, Marc Zyngier wrote: >> Hi Andrew, >> >> On 09/01/2019 14:24, Andrew Murray wrote: >>> On Wed, Jan 09, 2019 at 01:54:34PM +0000, Marc Zyngier wrote: >>>> When running VHE, there is no need to jump via some stub to perform >>>> a "HYP" function call, as there is a single address space. >>>> >>>> Let's thus change kvm_call_hyp() and co to perform a direct call >>>> in this case. Although this results in a bit of code expansion, >>>> it allows the compiler to check for type compatibility, something >>>> that we are missing so far. >>>> >>>> Signed-off-by: Marc Zyngier >>>> --- >>>> arch/arm64/include/asm/kvm_host.h | 32 +++++++++++++++++++++++++++++-- >>>> 1 file changed, 30 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >>>> index e54cb7c88a4e..df32edbadd69 100644 >>>> --- a/arch/arm64/include/asm/kvm_host.h >>>> +++ b/arch/arm64/include/asm/kvm_host.h >>>> @@ -370,8 +370,36 @@ void kvm_arm_halt_guest(struct kvm *kvm); >>>> void kvm_arm_resume_guest(struct kvm *kvm); >>>> >>>> u64 __kvm_call_hyp(void *hypfn, ...); >>>> -#define kvm_call_hyp(f, ...) __kvm_call_hyp(kvm_ksym_ref(f), ##__VA_ARGS__) >>>> -#define kvm_call_hyp_ret(f, ...) kvm_call_hyp(f, ##__VA_ARGS__) >>>> + >>>> +/* >>>> + * The couple of isb() below are there to guarantee the same behaviour >>>> + * on VHE as on !VHE, where the eret to EL1 acts as a context >>>> + * synchronization event. >>>> + */ >>>> +#define kvm_call_hyp(f, ...) \ >>>> + do { \ >>>> + if (cpus_have_const_cap(ARM64_HAS_VIRT_HOST_EXTN)) { \ >>>> + f(__VA_ARGS__); \ >>>> + isb(); \ >>>> + } else { \ >>>> + __kvm_call_hyp(kvm_ksym_ref(f), ##__VA_ARGS__); \ >>>> + } \ >>>> + } while(0) >>>> + >>>> +#define kvm_call_hyp_ret(f, ...) \ >>>> + ({ \ >>>> + u64 ret; \ >>>> + \ >>>> + if (cpus_have_const_cap(ARM64_HAS_VIRT_HOST_EXTN)) { \ >>>> + ret = f(__VA_ARGS__); \ >>> >>> __kvm_get_mdcr_el2 and __kvm_vcpu_run_nvhe don't return u64 type, they >>> return a smaller type. I guess any issues would be picked up when compiling, >>> but should the name of the macro be clearer as to the assumptions it makes? >>> Or perhaps take an argument which is the type of ret? >> >> kvm_call_hyp has always returned a u64, so no semantic has changed here. >> >> Otherwise, your suggestion of specifying a return type is interesting, >> but it also gives the programmer another chance to shoot itself in the >> foot by not providing the return type corresponding to the function that >> is called. >> >> Unless we can extract the return type by pure magic, I'm not sure we >> gain much. >> > > Would the following work? > > typeof(f(__VA_ARGS__)) ret; > > If typeof works anything like sizeof, I'd expect it would evaluate stuff it wouldn't* > passed as argument and we'd have the return type of the function. > > Cheers, > -- Julien Thierry _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel