On 6/4/20 7:03 PM, Anchal Agarwal wrote:
> On Sat, May 30, 2020 at 07:02:01PM -0400, Boris Ostrovsky wrote:
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>>
>>
>>
>> On 5/19/20 7:25 PM, Anchal Agarwal wrote:
>>> Introduce a small function which re-uses shared page's PA allocated
>>> during guest initialization time in reserve_shared_info() and not
>>> allocate new page during resume flow.
>>> It also does the mapping of shared_info_page by calling
>>> xen_hvm_init_shared_info() to use the function.
>>>
>>> Signed-off-by: Anchal Agarwal <ancha...@amazon.com>
>>> ---
>>> arch/x86/xen/enlighten_hvm.c | 7 +++++++
>>> arch/x86/xen/xen-ops.h | 1 +
>>> 2 files changed, 8 insertions(+)
>>>
>>> diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
>>> index e138f7de52d2..75b1ec7a0fcd 100644
>>> --- a/arch/x86/xen/enlighten_hvm.c
>>> +++ b/arch/x86/xen/enlighten_hvm.c
>>> @@ -27,6 +27,13 @@
>>>
>>> static unsigned long shared_info_pfn;
>>>
>>> +void xen_hvm_map_shared_info(void)
>>> +{
>>> + xen_hvm_init_shared_info();
>>> + if (shared_info_pfn)
>>> + HYPERVISOR_shared_info = __va(PFN_PHYS(shared_info_pfn));
>>> +}
>>> +
>>
>> AFAICT it is only called once so I don't see a need for new routine.
>>
>>
> HYPERVISOR_shared_info can only be mapped in this scope without refactoring
> much of the code.
Refactoring what? All am suggesting is
--- a/arch/x86/xen/suspend.c
+++ b/arch/x86/xen/suspend.c
@@ -124,7 +124,9 @@ static void xen_syscore_resume(void)
return;
/* No need to setup vcpu_info as it's already moved off */
- xen_hvm_map_shared_info();
+ xen_hvm_init_shared_info();
+ if (shared_info_pfn)
+ HYPERVISOR_shared_info = __va(PFN_PHYS(shared_info_pfn));
pvclock_resume();
>> And is it possible for shared_info_pfn to be NULL in resume path (which
>> is where this is called)?
>>
>>
> I don't think it should be, still a sanity check but I don't think its needed
> there
> because hibernation will fail in any case if thats the case.
If shared_info_pfn is NULL you'd have problems long before hibernation
started. We set it in xen_hvm_guest_init() and never touch again.
In fact, I'd argue that it should be __ro_after_init.
> However, HYPERVISOR_shared_info does needs to be re-mapped on resume as its
> been
> marked to dummy address on suspend. Its also safe in case va changes.
> Does the answer your question?
I wasn't arguing whether HYPERVISOR_shared_info needs to be set, I was
only saying that shared_info_pfn doesn't need to be tested.
-boris
