On 04/05/2018 10:46 AM, Roger Pau Monné wrote: > On Thu, Apr 05, 2018 at 10:40:37AM +0100, George Dunlap wrote: >> On 04/05/2018 10:34 AM, Roger Pau Monné wrote: >>> On Wed, Apr 04, 2018 at 11:29:39PM +0800, Chao Gao wrote: >>>> ... the same page with other registers which are not relevant to MSI-X. Xen >>>> marks pages where PBA resides as read-only. When assigning such devices to >>>> guest, device driver writes MSI-X irrelevant registers on those pages would >>>> lead to an EPT violation and the guest is destroyed because no handler is >>>> registered for those address range. In order to make guest capable to use >>>> such >>>> kind of devices, trapping very frequent write accesses is not a good idea >>>> for >>>> it would significantly impact the performance. >>>> >>>> This patch provides a workaround with caveat. Specifically, an option is >>>> introduced to specify a list of devices. For those devices, Xen doesn't >>>> control the access right to pages where PBA resides. Hence, guest device >>>> driver is able to write those pages and functions well. Note that adding an >>>> untrusted device to this option may endanger security of the entire system. >>>> >>>> Signed-off-by: Chao Gao <chao....@intel.com> >>>> --- >>>> docs/misc/xen-command-line.markdown | 10 +++++++++ >>>> xen/arch/x86/msi.c | 7 ++++-- >>>> xen/drivers/passthrough/pci.c | 45 >>>> +++++++++++++++++++++++++++++++++++-- >>>> xen/include/asm-x86/msi.h | 1 + >>>> 4 files changed, 59 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/docs/misc/xen-command-line.markdown >>>> b/docs/misc/xen-command-line.markdown >>>> index b353352..e382513 100644 >>>> --- a/docs/misc/xen-command-line.markdown >>>> +++ b/docs/misc/xen-command-line.markdown >>>> @@ -1423,6 +1423,16 @@ Defaults to booting secondary processors. >>>> >>>> > Default: `on` >>>> >>>> +### pba\_quirk >>> >>> pba_write_allowed would be better, pba_quirk is too generic IMO. >> >> 'quirk' was I think requested by Jan; and my understanding is that the >> word clearly indicates that the behavior in question is a workaround for >> hardware which is not compliant with the appropriate specification. If >> you grep the source tree for 'quirk' you'll find a fairly large number. >> >> pba_shared_quirk might be slightly more descriptive. > > pba_write_quirk? > > I just think it should be slightly more descriptive than pba_quirk in > case Xen has to add further PBA-related quirks in the future.
"shared" tells you something about the quirk itself: The PBA is shared across multiple devices. "write" tells you about the work-around: unsafe writes to the PBA region are allowed. I think it makes more sense for the name to describe the quirk itself rather than the work-around. The description says what the work-around does and why it's unsafe. -George _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
