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Fri, 25 Sep 2020 15:08:23 +0000 From: Bertrand Marquis To: Stefano Stabellini CC: "linux-kernel@vger.kernel.org" , Stefano Stabellini , "boris.ostrovsky@oracle.com" , Juergen Gross Subject: Re: [PATCH] xen/arm: do not setup the runstate info page if kpti is enabled Thread-Topic: [PATCH] xen/arm: do not setup the runstate info page if kpti is enabled Thread-Index: AQHWks1x5K2MwRRKqk+mgjFvkj623Kl5ddAA Date: Fri, 25 Sep 2020 15:08:23 +0000 Message-ID: References: <20200924234955.15455-1-sstabellini@kernel.org> In-Reply-To: <20200924234955.15455-1-sstabellini@kernel.org> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: Authentication-Results-Original: kernel.org; dkim=none (message not signed) header.d=none;kernel.org; dmarc=none action=none header.from=arm.com; x-originating-ip: [82.24.250.194] x-ms-publictraffictype: Email X-MS-Office365-Filtering-HT: Tenant X-MS-Office365-Filtering-Correlation-Id: ba264659-2cb4-4491-addb-08d86164dd98 x-ms-traffictypediagnostic: DB6PR08MB2870:|VE1PR08MB5775: X-Microsoft-Antispam-PRVS: x-checkrecipientrouted: true nodisclaimer: true x-ms-oob-tlc-oobclassifiers: OLM:7691;OLM:9508; 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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Sep 2020 15:08:31.5259 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ba264659-2cb4-4491-addb-08d86164dd98 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: DB5EUR03FT026.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: VE1PR08MB5775 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, > On 25 Sep 2020, at 00:49, Stefano Stabellini wro= te: > > From: Stefano Stabellini > > The VCPUOP_register_runstate_memory_area hypercall takes a virtual > address of a buffer as a parameter. The semantics of the hypercall are > such that the virtual address should always be valid. > > When KPTI is enabled and we are running userspace code, the virtual > address is not valid, thus, Linux is violating the semantics of > VCPUOP_register_runstate_memory_area. > > Do not call VCPUOP_register_runstate_memory_area when KPTI is enabled. > > Signed-off-by: Stefano Stabellini Reviewed-by: Bertrand Marquis I tested this on an Arm64 FVP and Errors generated by Xen are not present a= nymore. Thanks a lot for the patch Stefano. Cheers, Bertrand > CC: Bertrand Marquis > CC: boris.ostrovsky@oracle.com > CC: jgross@suse.com > --- > arch/arm/include/asm/xen/page.h | 5 +++++ > arch/arm/xen/enlighten.c | 6 ++++-- > arch/arm64/include/asm/xen/page.h | 6 ++++++ > 3 files changed, 15 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/p= age.h > index 31bbc803cecb..dc7f6e91aafa 100644 > --- a/arch/arm/include/asm/xen/page.h > +++ b/arch/arm/include/asm/xen/page.h > @@ -1 +1,6 @@ > #include > + > +static inline bool xen_kernel_unmapped_at_usr(void) > +{ > +return false; > +} > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c > index e93145d72c26..ea76562af1e9 100644 > --- a/arch/arm/xen/enlighten.c > +++ b/arch/arm/xen/enlighten.c > @@ -158,7 +158,8 @@ static int xen_starting_cpu(unsigned int cpu) > BUG_ON(err); > per_cpu(xen_vcpu, cpu) =3D vcpup; > > -xen_setup_runstate_info(cpu); > +if (!xen_kernel_unmapped_at_usr()) > +xen_setup_runstate_info(cpu); > > after_register_vcpu_info: > enable_percpu_irq(xen_events_irq, 0); > @@ -387,7 +388,8 @@ static int __init xen_guest_init(void) > return -EINVAL; > } > > -xen_time_setup_guest(); > +if (!xen_kernel_unmapped_at_usr()) > +xen_time_setup_guest(); > > if (xen_initial_domain()) > pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier); > diff --git a/arch/arm64/include/asm/xen/page.h b/arch/arm64/include/asm/x= en/page.h > index 31bbc803cecb..dffdc773221b 100644 > --- a/arch/arm64/include/asm/xen/page.h > +++ b/arch/arm64/include/asm/xen/page.h > @@ -1 +1,7 @@ > #include > +#include > + > +static inline bool xen_kernel_unmapped_at_usr(void) > +{ > +return arm64_kernel_unmapped_at_el0(); > +} > -- > 2.17.1 > IMPORTANT NOTICE: The contents of this email and any attachments are confid= ential and may also be privileged. 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