Re: [Xen-devel] [PATCH v5 3/4] x86/ioreq server: Add HVMOP to map guest ram with p2m_ioreq_server to an ioreq server.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.08.16 at 10:47, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
> On 8/10/2016 6:43 PM, Yu Zhang wrote:
>> For " && p2mt != p2m_ioreq_server" condition, it is just to guarantee 
>> that if a write
>> operation is trapped, and at the same period, device model changed the 
>> status of
>> ioreq server, it should be discarded.
> 
> Hi Paul & Jan, any comments?

Didn't Paul's "should behave like p2m_ram_rw" reply clarify things
sufficiently?

>> A second thought is, I am now more worried about the " && dir == 
>> IOREQ_WRITE"
>> condition, which we used previously to set s to NULL if it is not a 
>> write operation.
>> However, if HVM uses a read-modify-write instruction to operate on a 
>> write-protected
>> address, it will be treated as both read and write accesses in 
>> ept_handle_violation(). In
>> such situation, we need to emulate the read access first(by just 
>> returning the value being
>> fetched either in hypervisor or in device model), instead of 
>> discarding the read access.
> 
> Any suggestions about this guest read-modify-write instruction situation?
> Is my depiction clear? :)

Well, from your earlier reply I concluded that you'd just go ahead
and put this into patch form, which we'd then look at.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel