Re: [Xen-devel] [PATCH] x86: allow Dom0 read-only access to IO-APICs

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.05.13 at 08:55, Keir Fraser <keir.xen@xxxxxxxxx> wrote:
> On 02/05/2013 07:31, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> 
>> There are BIOSes that want to map the IO-APIC MMIO region from some
>> ACPI method(s), and there is at least one BIOS flavor that wants to
>> use this mapping to clear an RTE's mask bit. While we can't allow the
>> latter, we can permit reads and simply drop write attempts, leveraging
>> the already existing infrastructure introduced for dealing with AMD
>> IOMMUs' representation as PCI devices.
>> 
>> This fixes an interrupt setup problem on a system where _CRS evaluation
>> involved the above described BIOS/ACPI behavior, and is expected to
>> also deal with a boot time crash of pv-ops Linux upon encountering the
>> same kind of system.
>> 
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> mmio_ro_ranges is not specific to ioapic handling, so its initialisation
> should probably not go to init_ioapic_mappings()? If it is x86 specific (for
> now at least) then it could just go in __start_xen()?

Can certainly do that - I just followed it originally having been done
by its first user (which now happens to be IO-APIC code).

If I do so, I shall then also move declaration and definition into x86
specific files...

Jan

>> --- a/xen/arch/x86/domain_build.c
>> +++ b/xen/arch/x86/domain_build.c
>> @@ -1114,7 +1114,7 @@ int __init construct_dom0(
>>      for ( i = 0; i < nr_ioapics; i++ )
>>      {
>>          mfn = paddr_to_pfn(mp_ioapics[i].mpc_apicaddr);
>> -        if ( smp_found_config )
>> +        if ( !rangeset_contains_singleton(mmio_ro_ranges, mfn) )
>>              rc |= iomem_deny_access(dom0, mfn, mfn);
>>      }
>>  
>> --- a/xen/arch/x86/io_apic.c
>> +++ b/xen/arch/x86/io_apic.c
>> @@ -2468,6 +2468,9 @@ void __init init_ioapic_mappings(void)
>>      unsigned int i, idx = FIX_IO_APIC_BASE_0;
>>      union IO_APIC_reg_01 reg_01;
>>  
>> +    mmio_ro_ranges = rangeset_new(NULL, "r/o mmio ranges",
>> +                                  RANGESETF_prettyprint_hex);
>> +
>>      if ( smp_found_config )
>>          nr_irqs_gsi = 0;
>>      for ( i = 0; i < nr_ioapics; i++ )
>> @@ -2507,6 +2510,11 @@ void __init init_ioapic_mappings(void)
>>              reg_01.raw = io_apic_read(i, 1);
>>              nr_ioapic_entries[i] = reg_01.bits.entries + 1;
>>              nr_irqs_gsi += nr_ioapic_entries[i];
>> +
>> +            if ( rangeset_add_singleton(mmio_ro_ranges,
>> +                                        ioapic_phys >> PAGE_SHIFT) )
>> +                printk(KERN_ERR "Failed to mark IO-APIC page %lx
>> read-only\n",
>> +                       ioapic_phys);
>>          }
>>      }
>>  
>> --- a/xen/drivers/passthrough/pci.c
>> +++ b/xen/drivers/passthrough/pci.c
>> @@ -105,8 +105,6 @@ void __init pt_pci_init(void)
>>      radix_tree_init(&pci_segments);
>>      if ( !alloc_pseg(0) )
>>          panic("Could not initialize PCI segment 0\n");
>> -    mmio_ro_ranges = rangeset_new(NULL, "r/o mmio ranges",
>> -                                  RANGESETF_prettyprint_hex);
>>  }
>>  
>>  int __init pci_add_segment(u16 seg)
>> 
>> 
>> 




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