[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: Proposal for Porting Xen to Armv8-R64 - DraftA
Hi Julien, > -----Original Message----- > From: Julien Grall <julien@xxxxxxx> > Sent: 2022年3月3日 17:15 > To: Wei Chen <Wei.Chen@xxxxxxx>; Stefano Stabellini > <sstabellini@xxxxxxxxxx> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Bertrand Marquis > <Bertrand.Marquis@xxxxxxx>; Penny Zheng <Penny.Zheng@xxxxxxx>; Henry Wang > <Henry.Wang@xxxxxxx>; nd <nd@xxxxxxx> > Subject: Re: Proposal for Porting Xen to Armv8-R64 - DraftA > > Hi Wei, > > On 03/03/2022 01:35, Wei Chen wrote: > >>> 1. Assembly code for EL1 MPU context_switch > >> > >> This discussion reminds me when KVM decided to rewrite their context > >> switch from assembly to C. The outcome was the compiler is able to do a > >> better job than us when it comes to optimizing. > >> > >> With a C version, we could also share the save/restore code with 32-bit > >> and it is easier to read/maintain. > >> > >> So I would suggest to run some numbers to check if it really worth > >> implementing the MPU save/restore in assembly. > >> > > > > It's interesting to hear KVM guys have similar discussion. Yes, if the > > gains of assembly code is not very obvious, then reusing the code for > 32-bit > > would be more important. As our current platform (FVP) could not do very > > precise performance measurement. I want to keep current assembly code > there, > > when we have a platform that can do such measurement we can have a > thread > > to discuss it. > > I briefly looked at the code, the assembly version is not going to be > trivial to review and we don't know yet whether it has an advantage. So > I would say this should be the inverse here. > > We want the C version first until we can prove the assembly version is > better. > > My gut feeling is we will not need the assembly version. > Ok, we will rollback to C version. After we will finish the measurements, then we will discuss it again (if the assembly has enough gain). > Cheers, > > -- > Julien Grall
|
![]() |
Lists.xenproject.org is hosted with RackSpace, monitoring our |