On Mon, 5 Oct 2020 18:51:45 +0200
Cédric Le Goater <c...@kaod.org> wrote:
> The XIVE_ESB_SET_PQ_10 load operation is used to disable temporarily
> an interrupt source. If StoreEOI is active, a source could be left
> enabled if the load and store operations come out of order.
>
> QEMU makes use of this offset to quiesce the sources before a
> migration. Enforce the load-after-store ordering always when doing so
> without querying the characteristics of the sources on the host. The
> performance penalty will be very small for QEMU.
>
> Signed-off-by: Cédric Le Goater <c...@kaod.org>
> ---
Reviewed-by: Greg Kurz <gr...@kaod.org>
> include/hw/ppc/xive.h | 8 ++++++++
> hw/intc/spapr_xive_kvm.c | 12 ++++++++++++
> hw/intc/xive.c | 6 ++++++
> 3 files changed, 26 insertions(+)
>
> diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
> index 445eccfe6b73..39cd273f86d5 100644
> --- a/include/hw/ppc/xive.h
> +++ b/include/hw/ppc/xive.h
> @@ -279,6 +279,14 @@ static inline hwaddr xive_source_esb_mgmt(XiveSource
> *xsrc, int srcno)
> #define XIVE_ESB_SET_PQ_10 0xe00 /* Load */
> #define XIVE_ESB_SET_PQ_11 0xf00 /* Load */
>
> +/*
> + * Load-after-store ordering
> + *
> + * Adding this offset to the load address will enforce
> + * load-after-store ordering. This is required to use with StoreEOI.
> + */
> +#define XIVE_ESB_LD_ST_MO 0x40 /* Load-after-store ordering */
> +
> uint8_t xive_source_esb_get(XiveSource *xsrc, uint32_t srcno);
> uint8_t xive_source_esb_set(XiveSource *xsrc, uint32_t srcno, uint8_t pq);
>
> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
> index 66bf4c06fe55..d428422a7b72 100644
> --- a/hw/intc/spapr_xive_kvm.c
> +++ b/hw/intc/spapr_xive_kvm.c
> @@ -357,6 +357,18 @@ static uint64_t xive_esb_rw(XiveSource *xsrc, int srcno,
> uint32_t offset,
>
> static uint8_t xive_esb_read(XiveSource *xsrc, int srcno, uint32_t offset)
> {
> + /*
> + * The XIVE_ESB_SET_PQ_10 load operation is used to disable
> + * temporarily an interrupt source. If StoreEOI is active, a
> + * source could be left enabled if the load and store operations
> + * come out of order.
> + *
> + * Enforce the load-after-store ordering always.
> + */
> + if (offset == XIVE_ESB_SET_PQ_10) {
> + offset |= XIVE_ESB_LD_ST_MO;
> + }
> +
> return xive_esb_rw(xsrc, srcno, offset, 0, 0) & 0x3;
> }
>
> diff --git a/hw/intc/xive.c b/hw/intc/xive.c
> index 489e6256ef70..b710ba2df095 100644
> --- a/hw/intc/xive.c
> +++ b/hw/intc/xive.c
> @@ -998,6 +998,12 @@ static uint64_t xive_source_esb_read(void *opaque,
> hwaddr addr, unsigned size)
> case XIVE_ESB_SET_PQ_01 ... XIVE_ESB_SET_PQ_01 + 0x0FF:
> case XIVE_ESB_SET_PQ_10 ... XIVE_ESB_SET_PQ_10 + 0x0FF:
> case XIVE_ESB_SET_PQ_11 ... XIVE_ESB_SET_PQ_11 + 0x0FF:
> + if (offset == XIVE_ESB_SET_PQ_10 &&
> + xsrc->esb_flags & XIVE_SRC_STORE_EOI) {
> + qemu_log_mask(LOG_GUEST_ERROR, "XIVE: load-after-store ordering "
> + "not enforced with Store EOI active for IRQ %d\n",
> + srcno);
> + }
> ret = xive_source_esb_set(xsrc, srcno, (offset >> 8) & 0x3);
> break;
> default:
