Re: [Xen-devel] [PATCH] xen: support 52 bit physical addresses in pv guests

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 21/09/17 17:00, Boris Ostrovsky wrote:
>
>>
>>>
>>>>
>>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>>> ---
>>>>    arch/x86/include/asm/xen/page.h | 11 ++++++++++-
>>>>    arch/x86/xen/mmu_pv.c           |  4 ++--
>>>>    2 files changed, 12 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/arch/x86/include/asm/xen/page.h
>>>> b/arch/x86/include/asm/xen/page.h
>>>> index 07b6531813c4..bcb8b193c8d1 100644
>>>> --- a/arch/x86/include/asm/xen/page.h
>>>> +++ b/arch/x86/include/asm/xen/page.h
>>>> @@ -26,6 +26,15 @@ typedef struct xpaddr {
>>>>        phys_addr_t paddr;
>>>>    } xpaddr_t;
>>>>    +#ifdef CONFIG_X86_64
>>>> +#define XEN_PHYSICAL_MASK    ((1UL << 52) - 1)
>>>
>>>
>>> SME is not supported for PV guests but for consistency (and in case sme
>>> bit somehow gets set)
>>> #define XEN_PHYSICAL_MASK    __sme_clr(((1UL << 52) - 1))
>>
>> Hmm, really? Shouldn't we rather add something like
>>
>> BUG_ON(sme_active());
>>
>> somewhere?
>
> We can do that too.

Please don't do anything to cause Linux to crash if Xen is using SME 
itself, but leaving all of the PV guest unencrypted.

~Andrew