Re: [Xen-devel] incorrect layout of globals from head_64.S during kexec boot

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 15/07/2012 17:06, "Olaf Hering" <olaf@xxxxxxxxx> wrote:

> On Tue, Jul 10, Keir Fraser wrote:
> 
>> Best thing to do, is possible, is map the shared-info page in the
>> xen-platform pci device's BAR memory range. Then it will not conflict with
>> any RAM.
> 
> This patch does that. I did a kexec boot and a save/restore.
> It does not deal with the possible race were the old pfn is not backed
> by a mfn.

Looks good to me.

 -- Keir

> Olaf
> 
> 
> commit a9d5567c67a2317c9db174a4deef6c5690220749
> Author: Olaf Hering <olaf@xxxxxxxxx>
> Date:   Thu Jul 12 19:38:39 2012 +0200
> 
>     xen PVonHVM: move shared info page from RAM to MMIO
>     
>     Signed-off-by: Olaf Hering <ohering@xxxxxxx>
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index ff962d4..8a743af 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1465,23 +1465,22 @@ static int init_hvm_pv_info(int *major, int *minor)
> return 0;
>  }
>  
> -void __ref xen_hvm_init_shared_info(void)
> +static struct shared_info *hvm_shared_info;
> +static unsigned long hvm_shared_info_pfn;
> +
> +static void __ref set_shared_info(struct shared_info *sip, unsigned long pfn)
>  {
> int cpu;
> struct xen_add_to_physmap xatp;
> - static struct shared_info *shared_info_page = 0;
>  
> - if (!shared_info_page)
> -  shared_info_page = (struct shared_info *)
> -   extend_brk(PAGE_SIZE, PAGE_SIZE);
> xatp.domid = DOMID_SELF;
> xatp.idx = 0;
> xatp.space = XENMAPSPACE_shared_info;
> - xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
> + xatp.gpfn = pfn;
> if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
> BUG();
>  
> - HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
> + HYPERVISOR_shared_info = sip;
>  
> /* xen_vcpu is a pointer to the vcpu_info struct in the shared_info
> * page, we use it in the event channel upcall and in some pvclock
> @@ -1494,8 +1493,48 @@ void __ref xen_hvm_init_shared_info(void)
> for_each_online_cpu(cpu) {
> per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
> }
> + mb();
>  }
>  
> +/* Reconnect the pfn to a mfn */
> +void __ref xen_hvm_resume_shared_info(void)
> +{
> + set_shared_info(hvm_shared_info, hvm_shared_info_pfn);
> +}
> +
> +/* Move the pfn in RAM to a pfn in MMIO space */
> +void __ref xen_hvm_finalize_shared_info(struct shared_info *sip, unsigned
> long pfn)
> +{
> + struct xen_memory_reservation reservation = {
> +  .domid = DOMID_SELF,
> +  .nr_extents = 1,
> + };
> + int rc;
> +
> + set_xen_guest_handle(reservation.extent_start, &hvm_shared_info_pfn);
> +
> + /* Move pfn, disconnects previous pfn from mfn */
> + set_shared_info(sip, pfn);
> +
> + /* Allocate new mfn for previous pfn */
> + rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
> + WARN_ON(rc != 1);
> +
> + /* Remember final pfn and pointer for resume */
> + hvm_shared_info_pfn = pfn;
> + hvm_shared_info = sip;
> +}
> +
> +/* Use a pfn in RAM until PCI init is done. */
> +static void __ref xen_hvm_initial_shared_info(void)
> +{
> + /* FIXME simply allocate a page and release it after pfn move (How at this
> stage?) */
> + hvm_shared_info = extend_brk(PAGE_SIZE, PAGE_SIZE);
> + hvm_shared_info_pfn = __pa(hvm_shared_info) >> PAGE_SHIFT;
> + set_shared_info(hvm_shared_info, hvm_shared_info_pfn);
> +}
> +
> +
>  #ifdef CONFIG_XEN_PVHVM
>  static int __cpuinit xen_hvm_cpu_notify(struct notifier_block *self,
>    unsigned long action, void *hcpu)
> @@ -1526,7 +1565,7 @@ static void __init xen_hvm_guest_init(void)
> if (r < 0)
> return;
>  
> - xen_hvm_init_shared_info();
> + xen_hvm_initial_shared_info();
>  
> if (xen_feature(XENFEAT_hvm_callback_vector))
> xen_have_vector_callback = 1;
> diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
> index 45329c8..ae8a00c 100644
> --- a/arch/x86/xen/suspend.c
> +++ b/arch/x86/xen/suspend.c
> @@ -30,7 +30,7 @@ void xen_arch_hvm_post_suspend(int suspend_cancelled)
>  {
>  #ifdef CONFIG_XEN_PVHVM
> int cpu;
> - xen_hvm_init_shared_info();
> + xen_hvm_resume_shared_info();
> xen_callback_vector();
> xen_unplug_emulated_devices();
> if (xen_feature(XENFEAT_hvm_safe_pvclock)) {
> diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
> index 202d4c1..1e4329e 100644
> --- a/arch/x86/xen/xen-ops.h
> +++ b/arch/x86/xen/xen-ops.h
> @@ -41,7 +41,7 @@ void xen_enable_syscall(void);
>  void xen_vcpu_restore(void);
>  
>  void xen_callback_vector(void);
> -void xen_hvm_init_shared_info(void);
> +void xen_hvm_resume_shared_info(void);
>  void xen_unplug_emulated_devices(void);
>  
>  void __init xen_build_dynamic_phys_to_machine(void);
> diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
> index 97ca359..cbe866b 100644
> --- a/drivers/xen/platform-pci.c
> +++ b/drivers/xen/platform-pci.c
> @@ -108,6 +108,8 @@ static int __devinit platform_pci_init(struct pci_dev
> *pdev,
> long ioaddr;
> long mmio_addr, mmio_len;
> unsigned int max_nr_gframes;
> + unsigned long addr;
> + struct shared_info *hvm_shared_info;
>  
> if (!xen_domain())
> return -ENODEV;
> @@ -138,6 +140,11 @@ static int __devinit platform_pci_init(struct pci_dev
> *pdev,
> platform_mmio = mmio_addr;
> platform_mmiolen = mmio_len;
>  
> + addr = alloc_xen_mmio(PAGE_SIZE);
> + hvm_shared_info = ioremap(addr, PAGE_SIZE);
> + memset(hvm_shared_info, 0, PAGE_SIZE);
> + xen_hvm_finalize_shared_info(hvm_shared_info, addr >> PAGE_SHIFT);
> +
> if (!xen_have_vector_callback) {
> ret = xen_allocate_irq(pdev);
> if (ret) {
> diff --git a/include/xen/events.h b/include/xen/events.h
> index 04399b2..3337698 100644
> --- a/include/xen/events.h
> +++ b/include/xen/events.h
> @@ -58,6 +58,8 @@ void notify_remote_via_irq(int irq);
>  
>  void xen_irq_resume(void);
>  
> +void xen_hvm_finalize_shared_info(struct shared_info *sip, unsigned long
> pfn);
> +
>  /* Clear an irq's pending state, in preparation for polling on it */
>  void xen_clear_irq_pending(int irq);
>  void xen_set_irq_pending(int irq);



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