Re: questions of vm save/restore on arm64

[Stefano Stabellini <sstabellini@kernel.org>]

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On Fri, 27 May 2016, Chenxiao Zhao wrote:
> Hi, 
> 
> My board is Hikey on which have octa-core of arm cortex-a53. I have applied patches [1] to try vm save/restore on arm.
> These patches originally do not working on arm64. I have made some changes based on patch set [2].

Hello Chenxiao,

thanks for your interest in Xen on ARM save/restore.


> What I have got so far is
> 
> 1. if I run 'xl save -p guest memState' to leave guest in suspend state, then run 'xl unpause guest'.
>     the guest can resume successfully. so I suppose the guest works find on suspend/resume. 
> 
> 2. if I run 'xl restore -p memState' to restore guest and use xenctx to dump all vcpu's registers.
>     all the registers are identical to the state on save. After I run 'xl unpause guest', I got no error but can not connect to console.
> After restore the guest's PC is at a function called user_disable_single_step(), which is called by single_step_handler(). 
> 
> My question is
> 
> 1. How could I debug guest on restore progress? are there any tools available?

Nothing special. You can use ctrl-AAA on the console to switch to the
hypervisor console and see the state of the guest. You can also add some
debug printks; if the console doesn't work you can use
dom0_write_console in Linux to get messages out of your guest (you need
to compile Xen with debug=y for that to work).


> 2. From my understanding, the restore not working is because some status is missing when saving.
>  e.g. on cpu_save, it know the domain is 64bit, but on cpu_load, it always think it is a 32bit domain. so I have hard coded the domain type to
> DOMAIN_64BIT.
> Am I correct?

If Xen thinks the domain is 32-bit at restore, it must be a bug.


> 3. How could I dump all VM's status? I only found xenctx can dump vcpu's registers.

You can use the hypervisor console via the ctrl-aaa menu.


> I have attached my patch and log below.
> 
> Looking forward for your feedback.
> Thanks
> 
> xl list
> Name                                        ID   Mem VCPUs      State   Time(s)
> Domain-0                                     0  1024     8     r-----      11.7
> root@linaro-alip:~# xl create guest.cfg
> Parsing config from guest.cfg
> [   39.238723] xen-blkback: ring-ref 8, event-channel 3, protocol 1 (arm-abi) persistent grants
> 
> root@linaro-alip:~# xl save -p guest memState
> Saving to memState new xl format (info 0x3/0x0/931)
> xc: info: Saving domain 1, type ARM
> (XEN) HVM1 save: VCPU
> (XEN) HVM1 save: A15_TIMER
> (XEN) HVM1 save: GICV2_GICD
> (XEN) HVM1 save: GICV2_GICC
> (XEN) HVM1 save: GICV3
> root@linaro-alip:~# /usr/lib/xen/bin/xenctx -a 1
> PC:       ffffffc0000ab028
> LR:       ffffffc00050458c
> ELR_EL1:  ffffffc000086b34
> CPSR:     200001c5
> SPSR_EL1: 60000145
> SP_EL0:   0000007ff6f2a850
> SP_EL1:   ffffffc0140a7ca0
> 
>  x0: 0000000000000001    x1: 00000000deadbeef    x2: 0000000000000002
>  x3: 0000000000000002    x4: 0000000000000004    x5: 0000000000000000
>  x6: 000000000000001b    x7: 0000000000000001    x8: 000000618e589e00
>  x9: 0000000000000000   x10: 0000000000000000   x11: 0000000000000000
> x12: 00000000000001a3   x13: 000000001911a7d9   x14: 0000000000002ee0
> x15: 0000000000000005   x16: 00000000deadbeef   x17: 0000000000000001
> x18: 0000000000000007   x19: 0000000000000000   x20: ffffffc014163d58
> x21: ffffffc014163cd8   x22: 0000000000000001   x23: 0000000000000140
> x24: ffffffc000d5bb18   x25: ffffffc014163cd8   x26: 0000000000000000
> x27: 0000000000000000   x28: 0000000000000000   x29: ffffffc0140a7ca0
> 
> SCTLR: 34d5d91d
> TTBCR: 00000032b5193519
> TTBR0: 002d000054876000
> TTBR1: 0000000040dcf000
> root@linaro-alip:~# xl destroy guest
> (XEN) mm.c:1265:d0v1 gnttab_mark_dirty not implemented yet
> root@linaro-alip:~# xl restore -p memState
> Loading new save file memState (new xl fmt info 0x3/0x0/931)
>  Savefile contains xl domain config in JSON format
> Parsing config from <saved>
> xc: info: (XEN) HVM2 restore: VCPU 0
> Found ARM domain from Xen 4.7
> xc: info: Restoring domain
> (XEN) HVM2 restore: A15_TIMER 0
> (XEN) HVM2 restore: A15_TIMER 0
> (XEN) HVM2 restore: GICV2_GICD 0
> (XEN) HVM2 restore: GICV2_GICC 0
> (XEN) GICH_LRs (vcpu 0) mask=0
> (XEN)    VCPU_LR[0]=0
> (XEN)    VCPU_LR[1]=0
> (XEN)    VCPU_LR[2]=0
> (XEN)    VCPU_LR[3]=0
> xc: info: Restore successful
> xc: info: XenStore: mfn 0x39001, dom 0, evt 1
> xc: info: Console: mfn 0x39000, dom 0, evt 2
> root@linaro-alip:~# /usr/lib/xen/bin/xenctx -a 2
> PC:       ffffffc0000ab028
> LR:       ffffffc00050458c
> ELR_EL1:  ffffffc000086b34
> CPSR:     200001c5
> SPSR_EL1: 60000145
> SP_EL0:   0000007ff6f2a850
> SP_EL1:   ffffffc0140a7ca0
> 
>  x0: 0000000000000000    x1: 00000000deadbeef    x2: 0000000000000002
>  x3: 0000000000000002    x4: 0000000000000004    x5: 0000000000000000
>  x6: 000000000000001b    x7: 0000000000000001    x8: 000000618e589e00
>  x9: 0000000000000000   x10: 0000000000000000   x11: 0000000000000000
> x12: 00000000000001a3   x13: 000000001911a7d9   x14: 0000000000002ee0
> x15: 0000000000000005   x16: 00000000deadbeef   x17: 0000000000000001
> x18: 0000000000000007   x19: 0000000000000000   x20: ffffffc014163d58
> x21: ffffffc014163cd8   x22: 0000000000000001   x23: 0000000000000140
> x24: ffffffc000d5bb18   x25: ffffffc014163cd8   x26: 0000000000000000
> x27: 0000000000000000   x28: 0000000000000000   x29: ffffffc0140a7ca0
> 
> SCTLR: 34d5d91d
> TTBCR: 00000000b5193519
> TTBR0: 002d000054876000
> TTBR1: 0000000040dcf000
> root@linaro-alip:~# xl unpause guest
> root@linaro-alip:~# xl list
> Name                                        ID   Mem VCPUs      State   Time(s)
> Domain-0                                     0  1024     8     r-----      22.2
> guest                                        2     0     1     r-----       4.8
> root@linaro-alip:~# /usr/lib/xen/bin/xenctx -a 2
> PC:       ffffffc000084a00
> LR:       ffffffc00050458c
> ELR_EL1:  ffffffc000084a00
> CPSR:     000003c5
> SPSR_EL1: 000003c5
> SP_EL0:   0000007ff6f2a850
> SP_EL1:   ffffffc0140a7ca0
> 
>  x0: 0000000000000000    x1: 00000000deadbeef    x2: 0000000000000002
>  x3: 0000000000000002    x4: 0000000000000004    x5: 0000000000000000
>  x6: 000000000000001b    x7: 0000000000000001    x8: 000000618e589e00
>  x9: 0000000000000000   x10: 0000000000000000   x11: 0000000000000000
> x12: 00000000000001a3   x13: 000000001911a7d9   x14: 0000000000002ee0
> x15: 0000000000000005   x16: 00000000deadbeef   x17: 0000000000000001
> x18: 0000000000000007   x19: 0000000000000000   x20: ffffffc014163d58
> x21: ffffffc014163cd8   x22: 0000000000000001   x23: 0000000000000140
> x24: ffffffc000d5bb18   x25: ffffffc014163cd8   x26: 0000000000000000
> x27: 0000000000000000   x28: 0000000000000000   x29: ffffffc0140a7ca0
> 
> SCTLR: 34d5d91d
> TTBCR: 00000000b5193519
> TTBR0: 002d000054876000
> TTBR1: 0000000040dcf000
> root@linaro-alip:~# xl console guest
> xenconsole: Could not read tty from store: Success
> root@linaro-alip:~#
> 
> 
> diff --git a/xen/arch/arm/hvm.c b/xen/arch/arm/hvm.c
> index aee3353..411bab4 100644
> --- a/xen/arch/arm/hvm.c
> +++ b/xen/arch/arm/hvm.c
> @@ -120,7 +120,8 @@ static int cpu_save(struct domain *d, hvm_domain_context_t *h)
>          ctxt.dfar = v->arch.dfar;
>          ctxt.dfsr = v->arch.dfsr;
>  #else
> -        /* XXX 64-bit */
> +       ctxt.far = v->arch.far;
> +       ctxt.esr = v->arch.esr;
>  #endif
> 
>  #ifdef CONFIG_ARM_32
> @@ -187,6 +188,9 @@ static int cpu_load(struct domain *d, hvm_domain_context_t *h)
>      if ( hvm_load_entry(VCPU, h, &ctxt) != 0 )
>          return -EINVAL;
> 
> +#ifdef CONFIG_ARM64
> +    v->arch.type = DOMAIN_64BIT;
> +#endif
>      v->arch.sctlr = ctxt.sctlr;
>      v->arch.ttbr0 = ctxt.ttbr0;
>      v->arch.ttbr1 = ctxt.ttbr1;
> @@ -199,7 +203,8 @@ static int cpu_load(struct domain *d, hvm_domain_context_t *h)
>      v->arch.dfar = ctxt.dfar;
>      v->arch.dfsr = ctxt.dfsr;
>  #else
> -    /* XXX 64-bit */
> +    v->arch.far = ctxt.far;
> +    v->arch.esr = ctxt.esr;
>  #endif
> 
>  #ifdef CONFIG_ARM_32
> diff --git a/xen/include/public/arch-arm/hvm/save.h b/xen/include/public/arch-arm/hvm/save.h
> index db916b1..89e6e89 100644
> --- a/xen/include/public/arch-arm/hvm/save.h
> +++ b/xen/include/public/arch-arm/hvm/save.h
> @@ -46,8 +46,12 @@ DECLARE_HVM_SAVE_TYPE(HEADER, 1, struct hvm_save_header);
> 
>  struct hvm_hw_cpu
>  {
> +#ifdef CONFIG_ARM_32
>      uint64_t vfp[34]; /* Vector floating pointer */
>      /* VFP v3 state is 34x64 bit, VFP v4 is not yet supported */
> +#else
> +    uint64_t vfp[66];
> +#endif
> 
>      /* Guest core registers */
>      struct vcpu_guest_core_regs core_regs;
> @@ -60,6 +64,9 @@ struct hvm_hw_cpu
>      uint32_t dacr;
>      uint64_t par;
> 
> +    uint64_t far;
> +    uint64_t esr;
> +
>      uint64_t mair0, mair1;
>      uint64_t tpidr_el0;
>      uint64_t tpidr_el1;
> 
> 
> 
> [1] http://lists.xen.org/archives/html/xen-devel/2015-12/msg01053.html
> [2] http://lists.xen.org/archives/html/xen-devel/2014-04/msg01544.html
> 
> 

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