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Re: [Qemu-devel] [PATCH] s390x/event-facility: variable-length event mas
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH] s390x/event-facility: variable-length event masks |
Date: |
Mon, 16 Oct 2017 15:44:33 +0200 |
On Wed, 11 Oct 2017 09:39:53 -0400
"Jason J. Herne" <address@hidden> wrote:
> From: Cornelia Huck <address@hidden>
Hey, blast from the past :)
>
> The architecture supports masks of variable length for sclp write
> event mask. We currently only support 4 byte event masks, as that
> is what Linux uses.
>
> Let's extend this to the maximum mask length supported by the
> architecture and return 0 to the guest for the mask bits we don't
> support in core.
>
> Initial patch by: Cornelia Huck <address@hidden>
>
> Signed-off-by: Cornelia Huck <address@hidden>
> Signed-off-by: Jason J. Herne <address@hidden>
> ---
> hw/s390x/event-facility.c | 35 +++++++++++++++++++++++++++++------
> include/hw/s390x/event-facility.h | 20 ++++++++++++++++----
> 2 files changed, 45 insertions(+), 10 deletions(-)
Out of curiousity: Do you have a guest that can verify this for mask
lengths != 4? Given that the guest I wrote that one for back then is
not publicly available...
>
> diff --git a/hw/s390x/event-facility.c b/hw/s390x/event-facility.c
> index 34b2faf..b0f71f4 100644
> --- a/hw/s390x/event-facility.c
> +++ b/hw/s390x/event-facility.c
> @@ -259,23 +259,46 @@ out:
> return;
> }
>
> +/* copy up to dst_len bytes and fill the rest of dst with zeroes */
> +static void copy_mask(uint8_t *dst, uint8_t *src, uint16_t dst_len,
> + uint16_t src_len)
> +{
> + int i;
> +
> + for (i = 0; i < dst_len; i++) {
> + dst[i] = i < src_len ? src[i] : 0;
> + }
> +}
> +
> static void write_event_mask(SCLPEventFacility *ef, SCCB *sccb)
> {
> WriteEventMask *we_mask = (WriteEventMask *) sccb;
> + uint16_t mask_length = be16_to_cpu(we_mask->mask_length);
> + uint32_t tmp_mask;
>
> - /* Attention: We assume that Linux uses 4-byte masks, what it actually
> - does. Architecture allows for masks of variable size, though */
> - if (be16_to_cpu(we_mask->mask_length) != 4) {
> + if (!mask_length || (mask_length > SCLP_EVENT_MASK_LEN_MAX)) {
> sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_MASK_LENGTH);
> goto out;
> }
>
> + /*
> + * Note: We currently only support masks up to 4 byte length;
> + * the remainder is filled up with zeroes. Linux uses
> + * a 4 byte mask length.
> + */
Do you have any plans for extending this? Or is there no need?
(I have to ask those questions, as the documentation is not publicly
available...)
> +
> /* keep track of the guest's capability masks */
> - ef->receive_mask = be32_to_cpu(we_mask->cp_receive_mask);
> + copy_mask((uint8_t *)&tmp_mask, WEM_CP_RECEIVE_MASK(we_mask,
> mask_length),
> + sizeof(tmp_mask), mask_length);
> + ef->receive_mask = be32_to_cpu(tmp_mask);
>
> /* return the SCLP's capability masks to the guest */
> - we_mask->send_mask = cpu_to_be32(get_host_send_mask(ef));
> - we_mask->receive_mask = cpu_to_be32(get_host_receive_mask(ef));
> + tmp_mask = cpu_to_be32(get_host_send_mask(ef));
> + copy_mask(WEM_RECEIVE_MASK(we_mask, mask_length), (uint8_t *)&tmp_mask,
> + mask_length, sizeof(tmp_mask));
> + tmp_mask = cpu_to_be32(get_host_receive_mask(ef));
> + copy_mask(WEM_SEND_MASK(we_mask, mask_length), (uint8_t *)&tmp_mask,
> + mask_length, sizeof(tmp_mask));
>
> sccb->h.response_code = cpu_to_be16(SCLP_RC_NORMAL_COMPLETION);
>
> diff --git a/include/hw/s390x/event-facility.h
> b/include/hw/s390x/event-facility.h
> index def1bb0..5119b9b 100644
> --- a/include/hw/s390x/event-facility.h
> +++ b/include/hw/s390x/event-facility.h
> @@ -49,16 +49,28 @@
> #define TYPE_SCLP_CPU_HOTPLUG "sclp-cpu-hotplug"
> #define TYPE_SCLP_QUIESCE "sclpquiesce"
>
> +#define SCLP_EVENT_MASK_LEN_MAX 1021
> +
> typedef struct WriteEventMask {
> SCCBHeader h;
> uint16_t _reserved;
> uint16_t mask_length;
> - uint32_t cp_receive_mask;
> - uint32_t cp_send_mask;
> - uint32_t receive_mask;
> - uint32_t send_mask;
> + uint8_t masks[];
> +/*
> + * Layout of the masks is
> + * uint8_t cp_receive_mask[mask_length];
> + * uint8_t cp_send_mask[mask_length];
> + * uint8_t receive_mask[mask_length];
> + * uint8_t send_mask[mask_length];
> + * where 1 <= mask_length <= SCLP_EVENT_MASK_LEN_MAX
> + */
> } QEMU_PACKED WriteEventMask;
>
> +#define WEM_CP_RECEIVE_MASK(wem, mask_len) ((wem)->masks)
> +#define WEM_CP_SEND_MASK(wem, mask_len) ((wem)->masks + (mask_len))
> +#define WEM_RECEIVE_MASK(wem, mask_len) ((wem)->masks + 2 * (mask_len))
> +#define WEM_SEND_MASK(wem, mask_len) ((wem)->masks + 3 * (mask_len))
> +
> typedef struct EventBufferHeader {
> uint16_t length;
> uint8_t type;
Patch looks reasonable as far as I can see (the documentation issue
again...)
Did you need to change much from the original patch?