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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 4/9] arm/vm_event: get/set registers
On 16/05/16 17:26, Tamas K Lengyel wrote: On May 16, 2016 09:59, "Julien Grall" <julien.grall@xxxxxxx <mailto:julien.grall@xxxxxxx>> wrote: >> > By defining 2 distinct structures, it will be more difficult for the >> introspection tools to inspect registers of an Aarch64 domain running in >> AArch32 mode. They wouldn't be able to re-use code for AArch32 domain >> because the structure fields are different. >> > >> > The ARM ARM (see D1.20.1 in ARM DDI 0487A.i) provides a mapping >> between AArch32 state and AArch64 state. If you use it to define the >> layout of a common structure, the support of AArch32 state for AArch64 >> domain will come free. >> > >> >> If the guest is running in 32-bit mode Xen will fill the 32-bit struct, >> so doing a common struct is not strictly necessary. It also requires a >> bunch if union declarations to match the names between that I would >> prefer to avoid. IMHO it's cleaner to do the struct definitions >> separately and then do a union on top. > > > That is not true. is_domain_32bit will check if the domain is configured to run 32-bit or 64-bit in EL1 (i.e the kernel level). > > So if you have a guest with 64-bit kernel and 32-bit userspace, Xen will always fill the 64-bit structure, even when the userspace is running. > Hm fair point. It complicates things a bit though either way as the event subscriber wouldn't know which mode it received the event from without doing some extra checks. So I guess Xen should transmit that information too, at which point it could also just pick the right struct to fill with the current setup. Not really, CPSR.M[4] tells you if the execution state were AArch32 or AArch64. vm_event_regs_* contains the cpsr fields, so the event subscriber can determine the mode.Actually, not all the registers in vm_event_regs_arm32 makes sense when the guest is a 64-bit domain. For instance, spsr_svc is for the EL1 (i.e kernel). Hence the suggestion to use a structure very similar to vcpu_guest_core_regs. Regards, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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