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

From: Thiago Jung Bauermann <[email-masked]>
Date: Fri, 03 Apr 2020 15:24:12 -0300

Ram Pai <[email-masked]> writes:

> On Tue, Mar 31, 2020 at 08:53:07PM -0300, Thiago Jung Bauermann wrote:
>> 
>> Hi Ram,
>> 
>> Ram Pai <[email-masked]> 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().  

Ah, my mistake. I misunderstood the code. Sorry for the noise and thanks
for clarifying.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center