Re: [Xen-devel] [PATCH V5 3/3] x86/altp2m: fix display frozen when switching to a new view early

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 11/14/18 7:55 AM, Tian, Kevin wrote:
>> From: Razvan Cojocaru [mailto:rcojocaru@xxxxxxxxxxxxxxx]
>> Sent: Sunday, November 11, 2018 10:07 PM
>>
>> When an new altp2m view is created very early on guest boot, the
>> display will freeze (although the guest will run normally). This
>> may also happen on resizing the display. The reason is the way
>> Xen currently (mis)handles logdirty VGA: it intentionally
>> misconfigures VGA pages so that they will fault.
>>
>> The problem is that it only does this in the host p2m. Once we
>> switch to a new altp2m, the misconfigured entries will no longer
>> fault, so the display will not be updated.
>>
>> This patch:
>> * updates ept_handle_misconfig() to use the active altp2m instead
>>   of the hostp2m;
>> * modifies p2m_change_entry_type_global(), p2m_memory_type_changed
>>   and p2m_change_type_range() to propagate their changes to all
>>   valid altp2ms.
>>
>> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
>> Suggested-by: George Dunlap <george.dunlap@xxxxxxxxxx>
>>
>> ---
>> CC: Jun Nakajima <jun.nakajima@xxxxxxxxx>
>> CC: Kevin Tian <kevin.tian@xxxxxxxxx>
>> CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
>> CC: Jan Beulich <jbeulich@xxxxxxxx>
>> CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
>>
>> ---
>> Changes since V4:
>>  - Now ASSERT()ing that altp2m is _not_ active in
>>    p2m_pt_handle_deferred_changes(), with added comment.
>>  - p2m_memory_type_changed() and p2m_change_type_range() now
>>    process altp2ms with the hostp2m lock taken.
>> ---
>>  xen/arch/x86/mm/p2m-ept.c |   8 ++++
>>  xen/arch/x86/mm/p2m-pt.c  |   8 ++++
>>  xen/arch/x86/mm/p2m.c     | 115
>> ++++++++++++++++++++++++++++++++++++++--------
>>  xen/include/asm-x86/p2m.h |   6 +--
>>  4 files changed, 114 insertions(+), 23 deletions(-)
>>
>> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
>> index fabcd06..e6fa85f 100644
>> --- a/xen/arch/x86/mm/p2m-ept.c
>> +++ b/xen/arch/x86/mm/p2m-ept.c
>> @@ -657,6 +657,9 @@ bool_t ept_handle_misconfig(uint64_t gpa)
>>      bool_t spurious;
>>      int rc;
>>
>> +    if ( altp2m_active(curr->domain) )
>> +        p2m = p2m_get_altp2m(curr);
>> +
>>      p2m_lock(p2m);
>>
>>      spurious = curr->arch.hvm.vmx.ept_spurious_misconfig;
>> @@ -1440,6 +1443,11 @@ void p2m_init_altp2m_ept(struct domain *d,
>> unsigned int i)
>>      struct p2m_domain *hostp2m = p2m_get_hostp2m(d);
>>      struct ept_data *ept;
>>
>> +    p2m->max_mapped_pfn = hostp2m->max_mapped_pfn;
>> +    p2m->default_access = hostp2m->default_access;
>> +    p2m->domain = hostp2m->domain;
>> +
>> +    p2m->global_logdirty = hostp2m->global_logdirty;
>>      p2m->ept.ad = hostp2m->ept.ad;
>>      p2m->min_remapped_gfn = gfn_x(INVALID_GFN);
>>      p2m->max_remapped_gfn = 0;
>> diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
>> index 55df185..3828088 100644
>> --- a/xen/arch/x86/mm/p2m-pt.c
>> +++ b/xen/arch/x86/mm/p2m-pt.c
>> @@ -29,6 +29,7 @@
>>  #include <xen/event.h>
>>  #include <xen/trace.h>
>>  #include <public/vm_event.h>
>> +#include <asm/altp2m.h>
>>  #include <asm/domain.h>
>>  #include <asm/page.h>
>>  #include <asm/paging.h>
>> @@ -464,6 +465,13 @@ int p2m_pt_handle_deferred_changes(uint64_t
>> gpa)
>>      struct p2m_domain *p2m = p2m_get_hostp2m(current->domain);
>>      int rc;
>>
>> +    /*
>> +     * Should altp2m ever be enabled for NPT / shadow use, this code
>> +     * should be updated to make use of the active altp2m, like
>> +     * ept_handle_misconfig().
>> +     */
>> +    ASSERT(!altp2m_active(current->domain));
>> +
>>      p2m_lock(p2m);
>>      rc = do_recalc(p2m, PFN_DOWN(gpa));
>>      p2m_unlock(p2m);
>> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
>> index 69536c1..c8561ba 100644
>> --- a/xen/arch/x86/mm/p2m.c
>> +++ b/xen/arch/x86/mm/p2m.c
>> @@ -277,7 +277,6 @@ int p2m_init(struct domain *d)
>>  int p2m_is_logdirty_range(struct p2m_domain *p2m, unsigned long start,
>>                            unsigned long end)
>>  {
>> -    ASSERT(p2m_is_hostp2m(p2m));
>>      if ( p2m->global_logdirty ||
>>           rangeset_contains_range(p2m->logdirty_ranges, start, end) )
>>          return 1;
>> @@ -286,31 +285,79 @@ int p2m_is_logdirty_range(struct p2m_domain
>> *p2m, unsigned long start,
>>      return 0;
>>  }
>>
>> +static void change_entry_type_global(struct p2m_domain *p2m,
>> +                                     p2m_type_t ot, p2m_type_t nt)
>> +{
>> +    p2m->change_entry_type_global(p2m, ot, nt);
>> +    p2m->global_logdirty = (nt == p2m_ram_logdirty);
>> +}
>> +
>>  void p2m_change_entry_type_global(struct domain *d,
>>                                    p2m_type_t ot, p2m_type_t nt)
>>  {
>> -    struct p2m_domain *p2m = p2m_get_hostp2m(d);
>> +    struct p2m_domain *hostp2m = p2m_get_hostp2m(d);
>>
>>      ASSERT(ot != nt);
>>      ASSERT(p2m_is_changeable(ot) && p2m_is_changeable(nt));
>>
>> -    p2m_lock(p2m);
>> -    p2m->change_entry_type_global(p2m, ot, nt);
>> -    p2m->global_logdirty = (nt == p2m_ram_logdirty);
>> -    p2m_unlock(p2m);
>> +    p2m_lock(hostp2m);
>> +
>> +    change_entry_type_global(hostp2m, ot, nt);
>> +
>> +#ifdef CONFIG_HVM
>> +    if ( unlikely(altp2m_active(d)) )
>> +    {
>> +        unsigned int i;
>> +
>> +        for ( i = 0; i < MAX_ALTP2M; i++ )
>> +            if ( d->arch.altp2m_eptp[i] != mfn_x(INVALID_MFN) )
>> +            {
>> +                struct p2m_domain *altp2m = d->arch.altp2m_p2m[i];
>> +
>> +                p2m_lock(altp2m);
>> +                change_entry_type_global(altp2m, ot, nt);
>> +                p2m_unlock(altp2m);
>> +            }
>> +    }
>> +#endif
>> +
>> +    p2m_unlock(hostp2m);
>> +}
>> +
>> +#ifdef CONFIG_HVM
>> +/* There's already a memory_type_changed() in asm/mtrr.h. */
>> +static void _memory_type_changed(struct p2m_domain *p2m)
>> +{
>> +    if ( p2m->memory_type_changed )
>> +        p2m->memory_type_changed(p2m);
>>  }
>>
>>  void p2m_memory_type_changed(struct domain *d)
> 
> why making whole p2m_memory_type_changed under CONFIG_HVM?

It has been requested by Jan and Wei in V3:

https://lists.xenproject.org/archives/html/xen-devel/2018-10/msg02495.html


Thanks,
Razvan

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