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b=W6fY7KPSvq9foEaC5JsE0+Kb3cAZDJmNXThl6O+K+5xm2CEvlDzr54Jd7yRITtegvzW3c5la8nBjBw8kzXiGSmkIKoV21xHeg5eKmj3FwWUPijUE1BfVek+SdCDJRsFWkpz0BgCobqvzIk0g+vzZUEPDEyrje2P1tKzITbrEjOg= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com; Date: Tue, 28 Apr 2026 15:59:56 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Thierry Escande Cc: xen-devel@lists.xenproject.org, Jan Beulich , Andrew Cooper , Anthony PERARD , Michal Orzel , Julien Grall , Stefano Stabellini Subject: Re: [PATCH 09/17] xev/hvm: Add HVMOP_get|set_ecam_space hypercalls Message-ID: References: <20260313163455.790692-1-thierry.escande@vates.tech> <20260313163455.790692-10-thierry.escande@vates.tech> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260313163455.790692-10-thierry.escande@vates.tech> X-ClientProxiedBy: MA3P292CA0018.ESPP292.PROD.OUTLOOK.COM (2603:10a6:250:47::19) To CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH7PR03MB7860:EE_|DM6PR03MB5180:EE_ X-MS-Office365-Filtering-Correlation-Id: 740c588c-b6ed-4ddd-b1f8-08dea52e7002 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|22082099003|18002099003|56012099003; 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> break; > > + case HVMOP_set_ecam_space: { > + xen_hvm_ecam_space_t ecam; > + struct domain *d; > + > + if ( copy_from_guest( &ecam, guest_handle_cast(arg, xen_hvm_ecam_space_t), 1 ) ) ^ extra space, here and at the closing parenthesis. Line length is also past the 80 character limit, same below in HVMOP_get_ecam_space. > + return -EFAULT; This operation (and the matching get variant) needs an XSM check. > + > + d = rcu_lock_domain_by_any_id(ecam.domid); > + if ( d == NULL ) > + return -ESRCH; > + > + if ( d->arch.ecam_addr ) { Coding style, opening braces should be on a new line. > + rcu_unlock_domain(d); > + return -EFAULT; This would better return -EBUSY > + } You also need to check the padding fields are 0. > + > + if ( (ecam.size >> 28) || (!ecam.addr) ) { ^ the parenthesis here are unneeded. > + rcu_unlock_domain(d); > + return -EINVAL; > + } > + > + d->arch.ecam_addr = ecam.addr; > + d->arch.ecam_size = ecam.size; I'm a bit worried about a domain being able to set it's own ECAM hole, assessing all the side-effects of this might be complex. Won't the code here better check the region passed in the hypercall is indeed not mapped in the p2m, so that trapping of ECAM accesses works as expected? Also, how does the ECAM hole get setup on native? I assume there are some magic registers in the PCI config space of a platform device that the firmware uses to position the ECAM space? Are those trapped by QEMU, in which case won't it be better to do it the native way (iow: with the config space registers), and let QEMU forward it to Xen? It would then be QEMU the one to call HVMOP_set_ecam_space (or whatever hypercall we end up using). > + > + rcu_unlock_domain(d); > + break; > + } > + > + case HVMOP_get_ecam_space: { > + xen_hvm_ecam_space_t ecam; > + struct domain *d; > + > + if ( copy_from_guest( &ecam, guest_handle_cast(arg, xen_hvm_ecam_space_t), 1 ) ) > + return -EFAULT; > + > + d = rcu_lock_domain_by_any_id(ecam.domid); > + if ( d == NULL ) > + return -ESRCH; > + > + if ( ! d->arch.ecam_addr || ! d->arch.ecam_size ) { > + rcu_unlock_domain(d); > + return -EINVAL; > + } > + > + ecam.addr = d->arch.ecam_addr; > + ecam.size = d->arch.ecam_size; > + rc = __copy_to_guest(arg, &ecam, 1) ? -EFAULT : 0; > + > + rcu_unlock_domain(d); > + break; > + } > + > default: > rc = -ENOSYS; > break; > diff --git a/xen/arch/x86/include/asm/domain.h b/xen/arch/x86/include/asm/domain.h > index ad7f6adb2c..24ec33fc4d 100644 > --- a/xen/arch/x86/include/asm/domain.h > +++ b/xen/arch/x86/include/asm/domain.h > @@ -476,6 +476,10 @@ struct arch_domain > > /* Emulated devices enabled bitmap. */ > uint32_t emulation_flags; > + > + /* PCI ECAM space emulation */ > + uint64_t ecam_addr; > + uint32_t ecam_size; This fields would better be in hvm_domain struct, and there you already have the mmcfg_regions list, which we should aim to use for the q35 introduced ECAM region. > } __cacheline_aligned; > > #ifdef CONFIG_HVM > diff --git a/xen/include/public/hvm/hvm_op.h b/xen/include/public/hvm/hvm_op.h > index e22adf0319..c84febc37c 100644 > --- a/xen/include/public/hvm/hvm_op.h > +++ b/xen/include/public/hvm/hvm_op.h > @@ -166,6 +166,17 @@ struct xen_hvm_get_mem_type { > typedef struct xen_hvm_get_mem_type xen_hvm_get_mem_type_t; > DEFINE_XEN_GUEST_HANDLE(xen_hvm_get_mem_type_t); > > +#define HVMOP_set_ecam_space 16 > +#define HVMOP_get_ecam_space 17 > +struct xen_hvm_ecam_space { > + domid_t domid; > + uint16_t pad[3]; /* align next field on 8-byte boundary */ > + uint64_t addr; > + uint32_t size; There's also a trailing uint32_t padding here on 64bit builds I think? FWIW, you could do: domid_t domid; uint16_t pad; uint32_t size uint64_t addr; As that would reduce the padding in the struct? Thanks, Roger.