Re: [Qemu-devel] [PATCH 2/2] target/i386: sev: Do not pin the ram device memory region

[Singh, Brijesh]

On 2/4/19 11:59 AM, Alex Williamson wrote:
> On Thu, 17 Jan 2019 21:53:16 +0000
> "Singh, Brijesh" <address@hidden> wrote:
> 
>> The RAM device presents a memory region that should be handled
>> as an IO region and should not be pinned.
>>
>> In the case of the vfio-pci, RAM device represents a MMIO BAR
>> and the memory region is not backed by pages hence
>> KVM_MEMORY_ENCRYPT_REG_REGION fails to lock the memory range.
>>
>> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1667249
>> Cc: Alex Williamson <address@hidden>
>> Cc: Paolo Bonzini <address@hidden>
>> Signed-off-by: Brijesh Singh <address@hidden>
>> ---
>>   target/i386/sev.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/target/i386/sev.c b/target/i386/sev.c
>> index 20b2d325d8..3e9d5c02fa 100644
>> --- a/target/i386/sev.c
>> +++ b/target/i386/sev.c
>> @@ -131,6 +131,17 @@ sev_ram_block_added(RAMBlockNotifier *n, void *host, 
>> size_t size)
>>   {
>>       int r;
>>       struct kvm_enc_region range;
>> +    ram_addr_t offset;
>> +    MemoryRegion *mr;
>> +
>> +    mr = memory_region_from_host(host, &offset);
>> +    /*
>> +     * The RAM device presents a memory region that should be treated
>> +     * as IO region and should not be pinned.
>> +     */
>> +    if (memory_region_is_ram_device(mr)) {
>> +        return;
>> +    }
>>   
>>       range.addr = (__u64)(unsigned long)host;
>>       range.size = size;
> 
> 
> memory_region_from_host() can return NULL, which would give you a
> segfault at memory_region_is_ram_device(), so you might want to test mr
> on it's own first and decide which path that would take.  Thanks,
> 


Ah, thanks for catching it. I will fix in v2.