Re: [PATCH v2] powerpc/XIVE: SVM: share the event-queue page with the Hypervisor.

[Ram Pai <linuxram@us.ibm.com>]

On Tue, Mar 31, 2020 at 08:53:07PM -0300, Thiago Jung Bauermann wrote:
> 
> Hi Ram,
> 
> Ram Pai <linuxram@us.ibm.com> writes:
> 
> > diff --git a/arch/powerpc/sysdev/xive/spapr.c b/arch/powerpc/sysdev/xive/spapr.c
> > index 55dc61c..608b52f 100644
> > --- a/arch/powerpc/sysdev/xive/spapr.c
> > +++ b/arch/powerpc/sysdev/xive/spapr.c
> > @@ -26,6 +26,8 @@
> >  #include <asm/xive.h>
> >  #include <asm/xive-regs.h>
> >  #include <asm/hvcall.h>
> > +#include <asm/svm.h>
> > +#include <asm/ultravisor.h>
> >  
> >  #include "xive-internal.h"
> >  
> > @@ -501,6 +503,9 @@ static int xive_spapr_configure_queue(u32 target, struct xive_q *q, u8 prio,
> >  		rc = -EIO;
> >  	} else {
> >  		q->qpage = qpage;
> > +		if (is_secure_guest())
> > +			uv_share_page(PHYS_PFN(qpage_phys),
> > +					1 << xive_alloc_order(order));
> 
> If I understand this correctly, you're passing the number of bytes of
> the queue to uv_share_page(), but that ultracall expects the number of
> pages to be shared.


static inline u32 xive_alloc_order(u32 queue_shift)
{
        return (queue_shift > PAGE_SHIFT) ? (queue_shift - PAGE_SHIFT) : 0;
}

xive_alloc_order(order) returns the order of PAGE_SIZE pages.
Hence the value passed to uv_shared_pages is the number of pages,
and not the number of bytes.

BTW: I did verify through testing that it was indeed passing 1 page to the
uv_share_page().  

RP