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

From: Greg Kurz <[email-masked]>
Date: Thu, 26 Mar 2020 11:04:05 +0100

On Thu, 26 Mar 2020 01:38:47 -0700
Ram Pai <[email-masked]> wrote:

> XIVE interrupt controller use an Event Queue (EQ) to enqueue event
> notifications when an exception occurs. The EQ is a single memory page
> provided by the O/S defining a circular buffer, one per server and
> priority couple.
> 
> On baremetal, the EQ page is configured with an OPAL call. On pseries,
> an extra hop is necessary and the guest OS uses the hcall
> H_INT_SET_QUEUE_CONFIG to configure the XIVE interrupt controller.
> 
> The XIVE controller being Hypervisor privileged, it will not be allowed
> to enqueue event notifications for a Secure VM unless the EQ pages are
> shared by the Secure VM.
> 
> Hypervisor/Ultravisor still requires support for the TIMA and ESB page
> fault handlers. Until this is complete, QEMU can use the emulated XIVE
> device for Secure VMs, option "kernel_irqchip=off" on the QEMU pseries
> machine.
> 
> Cc: [email-masked]
> Cc: [email-masked]
> Cc: Michael Ellerman <[email-masked]>
> Cc: Thiago Jung Bauermann <[email-masked]>
> Cc: Michael Anderson <[email-masked]>
> Cc: Sukadev Bhattiprolu <[email-masked]>
> Cc: Alexey Kardashevskiy <[email-masked]>
> Cc: Paul Mackerras <[email-masked]>
> Cc: Greg Kurz <[email-masked]>
> Cc: Cedric Le Goater <[email-masked]>
> Cc: David Gibson <[email-masked]>
> Signed-off-by: Ram Pai <[email-masked]>
> 
> v2: better description of the patch from Cedric.
> ---

Reviewed-by: Greg Kurz <[email-masked]>

>  arch/powerpc/sysdev/xive/spapr.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> 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));
>  	}
>  fail:
>  	return rc;
> @@ -534,6 +539,8 @@ static void xive_spapr_cleanup_queue(unsigned int cpu, struct xive_cpu *xc,
>  		       hw_cpu, prio);
>  
>  	alloc_order = xive_alloc_order(xive_queue_shift);
> +	if (is_secure_guest())
> +		uv_unshare_page(PHYS_PFN(__pa(q->qpage)), 1 << alloc_order);
>  	free_pages((unsigned long)q->qpage, alloc_order);
>  	q->qpage = NULL;
>  }