The new xenstore page allocation scheme might break older unpatches Linux kernels that do not check for the Xenstore connection status before proceeding with Xenstore initialization.
Introduce a dom0less configuration option to retain the older behavior. The older behavior triggered by this option is to allocate the xenstore page in init-dom0less. That does not work with static-mem guests. However, it will make it possible to run as regular guests older Linux kernel versions that are left unpatched. Signed-off-by: Stefano Stabellini <[email protected]> --- Changes in v6: - improve wording in commit message and doc - code style - add separate alloc_xenstore_params function docs/misc/arm/device-tree/booting.txt | 5 +++ xen/arch/arm/dom0less-build.c | 45 +++++++++++++++++++-------- xen/arch/arm/include/asm/kernel.h | 30 +++++++++++------- 3 files changed, 56 insertions(+), 24 deletions(-) diff --git a/docs/misc/arm/device-tree/booting.txt b/docs/misc/arm/device-tree/booting.txt index 9c881baccc..4d6d859c66 100644 --- a/docs/misc/arm/device-tree/booting.txt +++ b/docs/misc/arm/device-tree/booting.txt @@ -222,6 +222,11 @@ with the following properties: Xen PV interfaces, including grant-table and xenstore, will be enabled for the VM. + - "legacy" + Same as above, but the way the xenstore page is allocated is not + compatible with static-mem guests. On the other hand, it works with + older Linux kernels. + - "disabled" Xen PV interfaces are disabled. diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c index 6c51f91999..56eb5c6da6 100644 --- a/xen/arch/arm/dom0less-build.c +++ b/xen/arch/arm/dom0less-build.c @@ -755,6 +755,30 @@ static int __init alloc_xenstore_page(struct domain *d) return 0; } +static int __init alloc_xenstore_params(struct domain *d, + struct kernel_info *kinfo) +{ + int rc = 0; + + if ( kinfo->dom0less_feature & (DOM0LESS_XENSTORE | DOM0LESS_XS_LEGACY) ) + { + ASSERT(hardware_domain); + rc = alloc_xenstore_evtchn(d); + if ( rc < 0 ) + return rc; + d->arch.hvm.params[HVM_PARAM_STORE_PFN] = ~0ULL; + } + + if ( kinfo->dom0less_feature & DOM0LESS_XENSTORE ) + { + rc = alloc_xenstore_page(d); + if ( rc < 0 ) + return rc; + } + + return rc; +} + static int __init construct_domU(struct domain *d, const struct dt_device_node *node) { @@ -800,6 +824,13 @@ static int __init construct_domU(struct domain *d, else panic("At the moment, Xenstore support requires dom0 to be present\n"); } + else if ( rc == 0 && !strcmp(dom0less_enhanced, "legacy") ) + { + if ( hardware_domain ) + kinfo.dom0less_feature = DOM0LESS_ENHANCED_LEGACY; + else + panic("At the moment, Xenstore support requires dom0 to be present\n"); + } else if ( rc == 0 && !strcmp(dom0less_enhanced, "no-xenstore") ) kinfo.dom0less_feature = DOM0LESS_ENHANCED_NO_XS; @@ -849,19 +880,7 @@ static int __init construct_domU(struct domain *d, if ( rc < 0 ) return rc; - if ( kinfo.dom0less_feature & DOM0LESS_XENSTORE ) - { - ASSERT(hardware_domain); - rc = alloc_xenstore_evtchn(d); - if ( rc < 0 ) - return rc; - - rc = alloc_xenstore_page(d); - if ( rc < 0 ) - return rc; - } - - return rc; + return alloc_xenstore_params(d, &kinfo); } void __init create_domUs(void) diff --git a/xen/arch/arm/include/asm/kernel.h b/xen/arch/arm/include/asm/kernel.h index de3f945ae5..bdc96f4c18 100644 --- a/xen/arch/arm/include/asm/kernel.h +++ b/xen/arch/arm/include/asm/kernel.h @@ -13,20 +13,28 @@ /* * List of possible features for dom0less domUs * - * DOM0LESS_ENHANCED_NO_XS: Notify the OS it is running on top of Xen. All the - * default features (excluding Xenstore) will be - * available. Note that an OS *must* not rely on the - * availability of Xen features if this is not set. - * DOM0LESS_XENSTORE: Xenstore will be enabled for the VM. This feature - * can't be enabled without the - * DOM0LESS_ENHANCED_NO_XS. - * DOM0LESS_ENHANCED: Notify the OS it is running on top of Xen. All the - * default features (including Xenstore) will be - * available. Note that an OS *must* not rely on the - * availability of Xen features if this is not set. + * DOM0LESS_ENHANCED_NO_XS: Notify the OS it is running on top of Xen. All the + * default features (excluding Xenstore) will be + * available. Note that an OS *must* not rely on the + * availability of Xen features if this is not set. + * DOM0LESS_XENSTORE: Xenstore will be enabled for the VM. The + * xenstore page allocation is done by Xen at + * domain creation. This feature can't be + * enabled without the DOM0LESS_ENHANCED_NO_XS. + * DOM0LESS_XS_LEGACY Xenstore will be enabled for the VM, the + * xenstore page allocation will happen in + * init-dom0less. This feature can't be enabled + * without the DOM0LESS_ENHANCED_NO_XS. + * DOM0LESS_ENHANCED: Notify the OS it is running on top of Xen. All the + * default features (including Xenstore) will be + * available. Note that an OS *must* not rely on the + * availability of Xen features if this is not set. + * DOM0LESS_ENHANCED_LEGACY: Same as before, but using DOM0LESS_XS_LEGACY. */ #define DOM0LESS_ENHANCED_NO_XS BIT(0, U) #define DOM0LESS_XENSTORE BIT(1, U) +#define DOM0LESS_XS_LEGACY BIT(2, U) +#define DOM0LESS_ENHANCED_LEGACY (DOM0LESS_ENHANCED_NO_XS | DOM0LESS_XS_LEGACY) #define DOM0LESS_ENHANCED (DOM0LESS_ENHANCED_NO_XS | DOM0LESS_XENSTORE) struct kernel_info { -- 2.25.1
