Re: crash on boot with 4.6.1 on fedora 24

[David Vrabel <david.vrabel@citrix.com>]

On 26/05/16 15:05, Boris Ostrovsky wrote:
> On 05/26/2016 06:24 AM, David Vrabel wrote:
>>> @@ -1577,10 +1577,10 @@ static pte_t __init mask_rw_pte(pte_t *ptep,
>>> pte_t pte)
>>>  	 * page tables for mapping the p2m list, too, and page tables MUST be
>>>  	 * mapped read-only.
>>>  	 */
>>> -	pfn = pte_pfn(pte);
>>> +	pfn = (pte & PTE_PFN_MASK) >> PAGE_SHIFT;
>>>  	if (pfn >= xen_start_info->first_p2m_pfn &&
>>>  	    pfn < xen_start_info->first_p2m_pfn + xen_start_info->nr_p2m_frames)
>>> -		pte = __pte_ma(pte_val_ma(pte) & ~_PAGE_RW);
>>> +		pte &= ~_PAGE_RW;
>>>
>>>  	return pte;
>>>  }
>>> @@ -1600,13 +1600,26 @@ static pte_t __init mask_rw_pte(pte_t *ptep,
>>> pte_t pte)
>>>   * so always write the PTE directly and rely on Xen trapping and
>>>   * emulating any updates as necessary.
>>>   */
>>> +__visible __init pte_t xen_make_pte_init(pteval_t pte)
>>> +{
>>> +#ifdef CONFIG_X86_64
>>> +	pte = mask_rw_pte(pte);
>>> +#endif
> 
> 
> Won't make_pte() be called on 32-bit as well? (And if yes then we can
> get rid of xen_set_pte_init())

Yes, but the 32-bit check needs the pointer to the PTE to see if it is
currently read-only, this isn't available in make_pte().

> (Also there were build warnings about xen_make_pte_init() being in wrong
> section because PV_CALLEE_SAVE is not __init).

I intent to fix this up before posting a v2.

David

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