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b=jCZmIBChTQurmXZOQU++Dpd2cQ9NGLVxDOCcQxmpr0+WiITOEiR/hSYEZyX+lCrZg RnTAe6OPPp5wqoTtCbyvYMB4UPIZUNoEKxLX668AoUQxMVufQUtOssXTw1C222PbDX ni7KeK9k5lSUknw90VfqL5zZXXPHu7CGpsX8JSaws70shWWtU0JQINwHBL+jHsSTek 9ldW7HXFKne6DfjQAZcOf4WqO3IdK/mFShEJ6+8hWIvCPAKHP9onWRHNucC4cRZQr1 EnI7w2pu6zFxUJqmW6p5jYeasMqjn71b9jMpOBkiycaHSQajZYYH49R7jGDOw4bx6E XQboQRYvrRkIQ== Date: Fri, 16 May 2025 18:06:56 +0000 To: Teddy Astie From: dmkhn@proton.me Cc: xen-devel@lists.xenproject.org, andrew.cooper3@citrix.com, anthony.perard@vates.tech, jbeulich@suse.com, julien@xen.org, michal.orzel@amd.com, roger.pau@citrix.com, sstabellini@kernel.org, dmukhin@ford.com Subject: Re: [PATCH v6 1/2] xen/domain: unify domain ID allocation Message-ID: In-Reply-To: <3c9f60b3-cedb-4689-a3b4-15ebddcf9f67@vates.tech> References: <20250516020434.1145337-1-dmukhin@ford.com> <20250516020434.1145337-2-dmukhin@ford.com> <3c9f60b3-cedb-4689-a3b4-15ebddcf9f67@vates.tech> Feedback-ID: 123220910:user:proton X-Pm-Message-ID: 550e272c748fe01b69429eddf7b387fcaccd2847 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Fri, May 16, 2025 at 08:43:35AM +0000, Teddy Astie wrote: > Hello, >=20 > Le 16/05/2025 =C3=A0 04:06, dmkhn@proton.me a =C3=A9crit=C2=A0: > > From: Denis Mukhin > > > > Currently, hypervisor code has two different non-system domain ID alloc= ation > > implementations: > > > > (a) Sequential IDs allocation in dom0less Arm code based on max_init= _domid; > > > > (b) Sequential IDs allocation in XEN_DOMCTL_createdomain; does not u= se > > max_init_domid (both Arm and x86). > > > > It makes sense to have a common helper code for such task across archit= ectures > > (Arm and x86) and between dom0less / toolstack domU allocation. > > > > Wrap the domain ID allocation as an arch-independent function domid_all= oc() in > > common/domain.c based on rangeset. > > > > Allocation algorithm: > > - If an explicit domain ID is provided, verify its availability and > > use it if ID is not used; > > - Otherwise, perform an exhaustive search starting from the end of the = used > > domain ID range. domid_alloc() guarantees that two subsequent calls = will > > result in different IDs allocation. > > > > Initialize the domain IDs rangeset from the new domid_init() which is c= alled > > from arch setup code. > > > > Also, remove is_free_domid() helper as it is not needed now. > > > > No functional change intended. > > > > Signed-off-by: Denis Mukhin > > --- > > Changes since v5: > > - rebased > > --- > > xen/arch/arm/domain_build.c | 17 ++++-- > > xen/arch/arm/setup.c | 2 + > > xen/arch/x86/setup.c | 13 +++-- > > xen/common/device-tree/dom0less-build.c | 10 ++-- > > xen/common/domain.c | 70 ++++++++++++++++++++++++= + > > xen/common/domctl.c | 41 ++------------- > > xen/include/xen/domain.h | 4 ++ > > 7 files changed, 107 insertions(+), 50 deletions(-) > > > > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c > > index b189a7cfae..e9d563c269 100644 > > --- a/xen/arch/arm/domain_build.c > > +++ b/xen/arch/arm/domain_build.c > > @@ -2010,6 +2010,7 @@ void __init create_dom0(void) > > .grant_opts =3D XEN_DOMCTL_GRANT_version(opt_gnttab_max_versi= on), > > }; > > unsigned int flags =3D CDF_privileged | CDF_hardware; > > + domid_t domid; > > int rc; > > > > /* The vGIC for DOM0 is exactly emulating the hardware GIC */ > > @@ -2034,19 +2035,25 @@ void __init create_dom0(void) > > if ( !llc_coloring_enabled ) > > flags |=3D CDF_directmap; > > > > - dom0 =3D domain_create(0, &dom0_cfg, flags); > > + domid =3D domid_alloc(0); > > + if ( domid =3D=3D DOMID_INVALID ) > > + panic("Error allocating domain ID 0\n"); > > + > > + dom0 =3D domain_create(domid, &dom0_cfg, flags); > > if ( IS_ERR(dom0) ) > > - panic("Error creating domain 0 (rc =3D %ld)\n", PTR_ERR(dom0))= ; > > + panic("Error creating domain %d (rc =3D %ld)\n", domid, PTR_ER= R(dom0)); > > > > if ( llc_coloring_enabled && (rc =3D dom0_set_llc_colors(dom0)) ) > > - panic("Error initializing LLC coloring for domain 0 (rc =3D %d= )\n", rc); > > + panic("Error initializing LLC coloring for domain %pd (rc =3D = %d)\n", > > + dom0, rc); > > > > if ( alloc_dom0_vcpu0(dom0) =3D=3D NULL ) > > - panic("Error creating domain 0 vcpu0\n"); > > + panic("Error creating domain %pdv0\n", dom0); > > > > rc =3D construct_dom0(dom0); > > if ( rc ) > > - panic("Could not set up DOM0 guest OS (rc =3D %d)\n", rc); > > + panic("Could not set up guest OS for domain %pd (rc =3D %d)\n"= , > > + dom0, rc); > > > > set_xs_domain(dom0); > > } > > diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c > > index 10b46d0684..c3959e8d8e 100644 > > --- a/xen/arch/arm/setup.c > > +++ b/xen/arch/arm/setup.c > > @@ -418,6 +418,8 @@ void asmlinkage __init start_xen(unsigned long fdt_= paddr) > > > > timer_init(); > > > > + domid_init(); > > + > > init_idle_domain(); > > > > rcu_init(); > > diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c > > index 2518954124..02f665f520 100644 > > --- a/xen/arch/x86/setup.c > > +++ b/xen/arch/x86/setup.c > > @@ -1030,8 +1030,11 @@ static struct domain *__init create_dom0(struct = boot_info *bi) > > if ( iommu_enabled ) > > dom0_cfg.flags |=3D XEN_DOMCTL_CDF_iommu; > > > > - /* Create initial domain. Not d0 for pvshim. */ > > - bd->domid =3D get_initial_domain_id(); > > + /* Allocate initial domain ID. Not d0 for pvshim. */ > > + bd->domid =3D domid_alloc(get_initial_domain_id()); > > + if ( bd->domid =3D=3D DOMID_INVALID ) > > + panic("Error allocating domain ID %d\n", get_initial_domain_id= ()); > > + > > d =3D domain_create(bd->domid, &dom0_cfg, > > pv_shim ? 0 : CDF_privileged | CDF_hardware); > > if ( IS_ERR(d) ) > > @@ -1063,7 +1066,7 @@ static struct domain *__init create_dom0(struct b= oot_info *bi) > > > > if ( (strlen(acpi_param) =3D=3D 0) && acpi_disabled ) > > { > > - printk("ACPI is disabled, notifying Domain 0 (acpi=3Doff)\= n"); > > + printk("ACPI is disabled, notifying domain %pd (acpi=3Doff= )\n", d); > > safe_strcpy(acpi_param, "off"); > > } > > > > @@ -1078,7 +1081,7 @@ static struct domain *__init create_dom0(struct b= oot_info *bi) > > > > bd->d =3D d; > > if ( construct_dom0(bd) !=3D 0 ) > > - panic("Could not construct domain 0\n"); > > + panic("Could not construct domain %pd\n", d); > > > > bd->cmdline =3D NULL; > > xfree(cmdline); > > @@ -1915,6 +1918,8 @@ void asmlinkage __init noreturn __start_xen(void) > > mmio_ro_ranges =3D rangeset_new(NULL, "r/o mmio ranges", > > RANGESETF_prettyprint_hex); > > > > + domid_init(); > > + > > xsm_multiboot_init(bi); > > > > /* > > diff --git a/xen/common/device-tree/dom0less-build.c b/xen/common/devic= e-tree/dom0less-build.c > > index 2c56f13771..9236dbae11 100644 > > --- a/xen/common/device-tree/dom0less-build.c > > +++ b/xen/common/device-tree/dom0less-build.c > > @@ -850,15 +850,13 @@ void __init create_domUs(void) > > struct xen_domctl_createdomain d_cfg =3D {0}; > > unsigned int flags =3D 0U; > > bool has_dtb =3D false; > > + domid_t domid; > > uint32_t val; > > int rc; > > > > if ( !dt_device_is_compatible(node, "xen,domain") ) > > continue; > > > > - if ( (max_init_domid + 1) >=3D DOMID_FIRST_RESERVED ) > > - panic("No more domain IDs available\n"); > > - > > d_cfg.max_evtchn_port =3D 1023; > > d_cfg.max_grant_frames =3D -1; > > d_cfg.max_maptrack_frames =3D -1; > > @@ -981,7 +979,11 @@ void __init create_domUs(void) > > * very important to use the pre-increment operator to call > > * domain_create() with a domid > 0. (domid =3D=3D 0 is reser= ved for Dom0) > > */ > > - d =3D domain_create(++max_init_domid, &d_cfg, flags); > > + domid =3D domid_alloc(++max_init_domid); > > + if ( domid =3D=3D DOMID_INVALID ) > > + panic("Error allocating ID for domain %s\n", dt_node_name(= node)); > > + > > + d =3D domain_create(domid, &d_cfg, flags); > > if ( IS_ERR(d) ) > > panic("Error creating domain %s (rc =3D %ld)\n", > > dt_node_name(node), PTR_ERR(d)); > > diff --git a/xen/common/domain.c b/xen/common/domain.c > > index abf1969e60..0ba3cdc47d 100644 > > --- a/xen/common/domain.c > > +++ b/xen/common/domain.c > > @@ -66,6 +66,74 @@ DEFINE_RCU_READ_LOCK(domlist_read_lock); > > static struct domain *domain_hash[DOMAIN_HASH_SIZE]; > > struct domain *domain_list; > > > > +/* Non-system domain ID allocator. */ > > +static DEFINE_SPINLOCK(domid_lock); > > +static struct rangeset *domid_rangeset; > > +static unsigned int domid_last; > > + > > +void __init domid_init(void) > > +{ > > + domid_rangeset =3D rangeset_new(NULL, "domid", RANGESETF_prettypri= nt_hex); > > + if ( !domid_rangeset ) > > + panic("cannot allocate domain ID rangeset\n"); > > + > > + rangeset_limit(domid_rangeset, DOMID_FIRST_RESERVED); > > +} > > + > > +/* > > + * Allocate new non-system domain ID based on the hint. > > + * > > + * If hint is outside of valid [0..DOMID_FIRST_RESERVED - 1] range of = IDs, > > + * perform an exhaustive search starting from the end of the used doma= in ID > > + * range. > > + */ > > +domid_t domid_alloc(domid_t domid) > > +{ > > + spin_lock(&domid_lock); > > + > > + if ( domid < DOMID_FIRST_RESERVED ) > > + { > > + if ( rangeset_contains_singleton(domid_rangeset, domid) ) > > + domid =3D DOMID_INVALID; > > + } > > + else > > + { > > + for ( domid =3D domid_last + 1; domid !=3D domid_last; domid++= ) > > + { > > + if ( domid =3D=3D DOMID_FIRST_RESERVED ) > > + domid =3D 0; > > + > > + if ( !rangeset_contains_singleton(domid_rangeset, domid) ) > > + break; > > + } > > + > > + if ( domid =3D=3D domid_last ) > > + domid =3D DOMID_INVALID; > > + } > > + > > + if ( domid !=3D DOMID_INVALID ) > > + { > > + ASSERT(!rangeset_add_singleton(domid_rangeset, domid)); > > + > > + if ( domid !=3D domid_last ) > > + domid_last =3D domid; > > + } > > + > > + spin_unlock(&domid_lock); > > + > > + return domid; > > +} >=20 > It's mostly a matter of implementation choice, but I am not really fan > of relying on rangesets, which to me are meant for address ranges or > something similar but at least large. >=20 > I would rather rely on a bitmap using find_first_zero_bit+set_bit which > avoids doing a per-domid test, and may be simpler overall. The bitmap > size for 0x3FF0 domains is almost 4KB, which looks acceptable. >=20 > I don't know what other thinks. Thanks for taking a look! TBH, I was initially considering using a bitmap. But then I chose use range= sets because statically defined bitmap will increase the binary size, which may = be indesirable; and for dynamic allocation, rangeset has all convenience APIs implemented... >=20 > > + > > +void domid_free(domid_t domid) > > +{ > > + spin_lock(&domid_lock); > > + > > + if ( rangeset_contains_singleton(domid_rangeset, domid) ) > > + ASSERT(!rangeset_remove_singleton(domid_rangeset, domid)); > > + > > + spin_unlock(&domid_lock); > > +} > > + > > /* > > * Insert a domain into the domlist/hash. This allows the domain to = be looked > > * up by domid, and therefore to be the subject of hypercalls/etc. > > @@ -1449,6 +1517,8 @@ void domain_destroy(struct domain *d) > > > > TRACE_TIME(TRC_DOM0_DOM_REM, d->domain_id); > > > > + domid_free(d->domain_id); > > + > > /* Remove from the domlist/hash. */ > > domlist_remove(d); > > > > diff --git a/xen/common/domctl.c b/xen/common/domctl.c > > index bfe2e1f9f0..2e02139660 100644 > > --- a/xen/common/domctl.c > > +++ b/xen/common/domctl.c > > @@ -49,20 +49,6 @@ static int xenctl_bitmap_to_nodemask(nodemask_t *nod= emask, > > MAX_NUMNODES); > > } > > > > -static inline int is_free_domid(domid_t dom) > > -{ > > - struct domain *d; > > - > > - if ( dom >=3D DOMID_FIRST_RESERVED ) > > - return 0; > > - > > - if ( (d =3D rcu_lock_domain_by_id(dom)) =3D=3D NULL ) > > - return 1; > > - > > - rcu_unlock_domain(d); > > - return 0; > > -} > > - > > void getdomaininfo(struct domain *d, struct xen_domctl_getdomaininfo = *info) > > { > > struct vcpu *v; > > @@ -421,34 +407,15 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_= t) u_domctl) > > > > case XEN_DOMCTL_createdomain: > > { > > - domid_t dom; > > - static domid_t rover =3D 0; > > + domid_t domid =3D domid_alloc(op->domain); > > > > - dom =3D op->domain; > > - if ( (dom > 0) && (dom < DOMID_FIRST_RESERVED) ) > > + if ( domid =3D=3D DOMID_INVALID ) > > { > > ret =3D -EEXIST; > > - if ( !is_free_domid(dom) ) > > - break; > > - } > > - else > > - { > > - for ( dom =3D rover + 1; dom !=3D rover; dom++ ) > > - { > > - if ( dom =3D=3D DOMID_FIRST_RESERVED ) > > - dom =3D 1; > > - if ( is_free_domid(dom) ) > > - break; > > - } > > - > > - ret =3D -ENOMEM; > > - if ( dom =3D=3D rover ) > > - break; > > - > > - rover =3D dom; > > + break; > > } > > > > - d =3D domain_create(dom, &op->u.createdomain, false); > > + d =3D domain_create(domid, &op->u.createdomain, false); > > if ( IS_ERR(d) ) > > { > > ret =3D PTR_ERR(d); >=20 > In case the domain creation failure, we need to free the domid, > otherwise, it would not be used anymore as considered used by the domid > allocator. Thanks! >=20 > > diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h > > index e10baf2615..039bb7eeaf 100644 > > --- a/xen/include/xen/domain.h > > +++ b/xen/include/xen/domain.h > > @@ -38,6 +38,10 @@ void arch_get_domain_info(const struct domain *d, > > > > domid_t get_initial_domain_id(void); > > > > +void domid_init(void); > > +void domid_free(domid_t domid); > > +domid_t domid_alloc(domid_t domid); > > + > > /* CDF_* constant. Internal flags for domain creation. */ > > /* Is this a privileged domain? */ > > #define CDF_privileged (1U << 0) >=20 > Teddy >=20 >=20 > Teddy Astie | Vates XCP-ng Developer >=20 > XCP-ng & Xen Orchestra - Vates solutions >=20 > web: https://vates.tech >=20 >=20 >=20