|
| From: | Mike Kowal |
| Subject: | Re: [PATCH 03/14] ppc/xive2: Support group-matching when looking for target |
| Date: | Mon, 2 Dec 2024 16:08:58 -0600 |
| User-agent: | Mozilla Thunderbird |
On 11/18/2024 9:22 PM, Nicholas Piggin wrote:
On Wed Oct 16, 2024 at 7:13 AM AEST, Michael Kowal wrote:
From: Frederic Barrat <fbarrat@linux.ibm.com>Multiple matches logic is a bit shoehorned into the match code here.
If an END has the 'i' bit set (ignore), then it targets a group of
VPs. The size of the group depends on the VP index of the target
(first 0 found when looking at the least significant bits of the
index) so a mask is applied on the VP index of a running thread to
know if we have a match.
Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Kowal <kowal@linux.ibm.com>
---
include/hw/ppc/xive.h | 5 +++-
include/hw/ppc/xive2.h | 1 +
hw/intc/pnv_xive2.c | 33 ++++++++++++++-------
hw/intc/xive.c | 56 +++++++++++++++++++++++++-----------
hw/intc/xive2.c | 65 ++++++++++++++++++++++++++++++------------
5 files changed, 114 insertions(+), 46 deletions(-)
diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
index 27ef6c1a17..a177b75723 100644
--- a/include/hw/ppc/xive.h
+++ b/include/hw/ppc/xive.h
@@ -424,6 +424,7 @@ void xive_router_end_notify(XiveRouter *xrtr, XiveEAS *eas);
typedef struct XiveTCTXMatch {
XiveTCTX *tctx;
uint8_t ring;
+ bool precluded;
} XiveTCTXMatch;
#define TYPE_XIVE_PRESENTER "xive-presenter"
@@ -452,7 +453,9 @@ int xive_presenter_tctx_match(XivePresenter *xptr, XiveTCTX *tctx,
bool xive_presenter_notify(XiveFabric *xfb, uint8_t format,
uint8_t nvt_blk, uint32_t nvt_idx,
bool cam_ignore, uint8_t priority,
- uint32_t logic_serv);
+ uint32_t logic_serv, bool *precluded);
+
+uint32_t xive_get_vpgroup_size(uint32_t nvp_index);
/*
* XIVE Fabric (Interface between Interrupt Controller and Machine)
diff --git a/include/hw/ppc/xive2.h b/include/hw/ppc/xive2.h
index 5bccf41159..17c31fcb4b 100644
--- a/include/hw/ppc/xive2.h
+++ b/include/hw/ppc/xive2.h
@@ -121,6 +121,7 @@ uint64_t xive2_tm_pull_os_ctx(XivePresenter *xptr, XiveTCTX *tctx,
hwaddr offset, unsigned size);
void xive2_tm_pull_os_ctx_ol(XivePresenter *xptr, XiveTCTX *tctx,
hwaddr offset, uint64_t value, unsigned size);
+bool xive2_tm_irq_precluded(XiveTCTX *tctx, int ring, uint8_t priority);
void xive2_tm_set_hv_target(XivePresenter *xptr, XiveTCTX *tctx,
hwaddr offset, uint64_t value, unsigned size);
void xive2_tm_pull_phys_ctx_ol(XivePresenter *xptr, XiveTCTX *tctx,
diff --git a/hw/intc/pnv_xive2.c b/hw/intc/pnv_xive2.c
index 834d32287b..3fb466bb2c 100644
--- a/hw/intc/pnv_xive2.c
+++ b/hw/intc/pnv_xive2.c
@@ -660,21 +660,34 @@ static int pnv_xive2_match_nvt(XivePresenter *xptr, uint8_t format,
logic_serv);
}
- /*
- * Save the context and follow on to catch duplicates,
- * that we don't support yet.
- */
if (ring != -1) {
- if (match->tctx) {
+ /*
+ * For VP-specific match, finding more than one is a
+ * problem. For group notification, it's possible.
+ */
+ if (!cam_ignore && match->tctx) {
qemu_log_mask(LOG_GUEST_ERROR, "XIVE: already found a "
"thread context NVT %x/%x\n",
nvt_blk, nvt_idx);
- return false;
+ /* Should set a FIR if we ever model it */
+ return -1;
+ }
+ /*
+ * For a group notification, we need to know if the
+ * match is precluded first by checking the current
+ * thread priority. If the interrupt can be delivered,
+ * we always notify the first match (for now).
+ */
+ if (cam_ignore &&
+ xive2_tm_irq_precluded(tctx, ring, priority)) {
+ match->precluded = true;
+ } else {
+ if (!match->tctx) {
+ match->ring = ring;
+ match->tctx = tctx;
+ }
+ count++;
"Return any best match" would be okay, but match->precluded could be set
to true for a non-precluded match if a different match was precluded.
And for VP directed interrupts, we can get a match from here which
*is* precluded, but has precluded = false!
It's a bit confusing.
typedef struct XiveTCTXMatch {
XiveTCTX *tctx;
uint8_t ring;
bool precluded;
} XiveTCTXMatch;
What if this was changed to be more clear it doesn't refer to a single
tctx? Something like -
XiveNVTMatches {
XiveTCTX *best_tctx;
uint8_t best_ring;
int match_count;
int precluded_group_match_count;
}
I'll have to wrap my head around this one... 😳 If I can not figure it out, I will et back to you.
}Should this also test PIPR?
-
- match->ring = ring;
- match->tctx = tctx;
- count++;
}
}
}
diff --git a/hw/intc/xive.c b/hw/intc/xive.c
index bacf518fa6..8ffcac4f65 100644
--- a/hw/intc/xive.c
+++ b/hw/intc/xive.c
@@ -1671,6 +1671,16 @@ static uint32_t xive_tctx_hw_cam_line(XivePresenter *xptr, XiveTCTX *tctx)
return xive_nvt_cam_line(blk, 1 << 7 | (pir & 0x7f));
}
+uint32_t xive_get_vpgroup_size(uint32_t nvp_index)
+{
+ /*
+ * Group size is a power of 2. The position of the first 0
+ * (starting with the least significant bits) in the NVP index
+ * gives the size of the group.
+ */
+ return 1 << (ctz32(~nvp_index) + 1);
+}
+
static uint8_t xive_get_group_level(uint32_t nvp_index)
{
/* FIXME add crowd encoding */
@@ -1743,30 +1753,39 @@ int xive_presenter_tctx_match(XivePresenter *xptr, XiveTCTX *tctx,
/*
* This is our simple Xive Presenter Engine model. It is merged in the
* Router as it does not require an extra object.
- *
- * It receives notification requests sent by the IVRE to find one
- * matching NVT (or more) dispatched on the processor threads. In case
- * of a single NVT notification, the process is abbreviated and the
- * thread is signaled if a match is found. In case of a logical server
- * notification (bits ignored at the end of the NVT identifier), the
- * IVPE and IVRE select a winning thread using different filters. This
- * involves 2 or 3 exchanges on the PowerBus that the model does not
- * support.
- *
- * The parameters represent what is sent on the PowerBus
*/
bool xive_presenter_notify(XiveFabric *xfb, uint8_t format,
uint8_t nvt_blk, uint32_t nvt_idx,
bool cam_ignore, uint8_t priority,
- uint32_t logic_serv)
+ uint32_t logic_serv, bool *precluded)
{
XiveFabricClass *xfc = XIVE_FABRIC_GET_CLASS(xfb);
- XiveTCTXMatch match = { .tctx = NULL, .ring = 0 };
+ XiveTCTXMatch match = { .tctx = NULL, .ring = 0, .precluded = false };
uint8_t group_level;
int count;
/*
- * Ask the machine to scan the interrupt controllers for a match
+ * Ask the machine to scan the interrupt controllers for a match.
+ *
+ * For VP-specific notification, we expect at most one match and
+ * one call to the presenters is all we need (abbreviated notify
+ * sequence documented by the architecture).
+ *
+ * For VP-group notification, match_nvt() is the equivalent of the
+ * "histogram" and "poll" commands sent to the power bus to the
+ * presenters. 'count' could be more than one, but we always
+ * select the first match for now. 'precluded' tells if (at least)
+ * one thread matches but can't take the interrupt now because
+ * it's running at a more favored priority. We return the
+ * information to the router so that it can take appropriate
+ * actions (backlog, escalation, broadcast, etc...)
+ *
+ * If we were to implement a better way of dispatching the
+ * interrupt in case of multiple matches (instead of the first
+ * match), we would need a heuristic to elect a thread (for
+ * example, the hardware keeps track of an 'age' in the TIMA) and
+ * a new command to the presenters (the equivalent of the "assign"
+ * power bus command in the documented full notify sequence.
*/
count = xfc->match_nvt(xfb, format, nvt_blk, nvt_idx, cam_ignore,
priority, logic_serv, &match);
@@ -1779,6 +1798,8 @@ bool xive_presenter_notify(XiveFabric *xfb, uint8_t format,
group_level = cam_ignore ? xive_get_group_level(nvt_idx) : 0;
trace_xive_presenter_notify(nvt_blk, nvt_idx, match.ring, group_level);
xive_tctx_pipr_update(match.tctx, match.ring, priority, group_level);
+ } else {
+ *precluded = match.precluded;
}
return !!count;
@@ -1818,7 +1839,7 @@ void xive_router_end_notify(XiveRouter *xrtr, XiveEAS *eas)
uint8_t nvt_blk;
uint32_t nvt_idx;
XiveNVT nvt;
- bool found;
+ bool found, precluded;
uint8_t end_blk = xive_get_field64(EAS_END_BLOCK, eas->w);
uint32_t end_idx = xive_get_field64(EAS_END_INDEX, eas->w);
@@ -1901,8 +1922,9 @@ void xive_router_end_notify(XiveRouter *xrtr, XiveEAS *eas)
found = xive_presenter_notify(xrtr->xfb, format, nvt_blk, nvt_idx,
xive_get_field32(END_W7_F0_IGNORE, end.w7),
priority,
- xive_get_field32(END_W7_F1_LOG_SERVER_ID, end.w7));
-
+ xive_get_field32(END_W7_F1_LOG_SERVER_ID, end.w7),
+ &precluded);
+ /* we don't support VP-group notification on P9, so precluded is not used */
/* TODO: Auto EOI. */
if (found) {
diff --git a/hw/intc/xive2.c b/hw/intc/xive2.c
index db372f4b30..2cb03c758e 100644
--- a/hw/intc/xive2.c
+++ b/hw/intc/xive2.c
@@ -739,6 +739,12 @@ int xive2_router_write_nvgc(Xive2Router *xrtr, bool crowd,
return xrc->write_nvgc(xrtr, crowd, nvgc_blk, nvgc_idx, nvgc);
}
+static bool xive2_vp_match_mask(uint32_t cam1, uint32_t cam2,
+ uint32_t vp_mask)
+{
+ return (cam1 & vp_mask) == (cam2 & vp_mask);
+}
+
/*
* The thread context register words are in big-endian format.
*/
@@ -753,44 +759,50 @@ int xive2_presenter_tctx_match(XivePresenter *xptr, XiveTCTX *tctx,
uint32_t qw1w2 = xive_tctx_word2(&tctx->regs[TM_QW1_OS]);
uint32_t qw0w2 = xive_tctx_word2(&tctx->regs[TM_QW0_USER]);
- /*
- * TODO (PowerNV): ignore mode. The low order bits of the NVT
- * identifier are ignored in the "CAM" match.
- */
+ uint32_t vp_mask = 0xFFFFFFFF;
if (format == 0) {
- if (cam_ignore == true) {
- /*
- * F=0 & i=1: Logical server notification (bits ignored at
- * the end of the NVT identifier)
- */
- qemu_log_mask(LOG_UNIMP, "XIVE: no support for LS NVT %x/%x\n",
- nvt_blk, nvt_idx);
- return -1;
+ /*
+ * i=0: Specific NVT notification
+ * i=1: VP-group notification (bits ignored at the end of the
+ * NVT identifier)
+ */
+ if (cam_ignore) {
+ vp_mask = ~(xive_get_vpgroup_size(nvt_idx) - 1);
}
- /* F=0 & i=0: Specific NVT notification */
+ /* For VP-group notifications, threads with LGS=0 are excluded */
/* PHYS ring */
if ((be32_to_cpu(qw3w2) & TM2_QW3W2_VT) &&
- cam == xive2_tctx_hw_cam_line(xptr, tctx)) {
+ !(cam_ignore && tctx->regs[TM_QW3_HV_PHYS + TM_LGS] == 0) &&
+ xive2_vp_match_mask(cam,
+ xive2_tctx_hw_cam_line(xptr, tctx),
+ vp_mask)) {
return TM_QW3_HV_PHYS;
}
/* HV POOL ring */
if ((be32_to_cpu(qw2w2) & TM2_QW2W2_VP) &&
- cam == xive_get_field32(TM2_QW2W2_POOL_CAM, qw2w2)) {
+ !(cam_ignore && tctx->regs[TM_QW2_HV_POOL + TM_LGS] == 0) &&
+ xive2_vp_match_mask(cam,
+ xive_get_field32(TM2_QW2W2_POOL_CAM, qw2w2),
+ vp_mask)) {
return TM_QW2_HV_POOL;
}
/* OS ring */
if ((be32_to_cpu(qw1w2) & TM2_QW1W2_VO) &&
- cam == xive_get_field32(TM2_QW1W2_OS_CAM, qw1w2)) {
+ !(cam_ignore && tctx->regs[TM_QW1_OS + TM_LGS] == 0) &&
+ xive2_vp_match_mask(cam,
+ xive_get_field32(TM2_QW1W2_OS_CAM, qw1w2),
+ vp_mask)) {
return TM_QW1_OS;
}
} else {
/* F=1 : User level Event-Based Branch (EBB) notification */
+ /* FIXME: what if cam_ignore and LGS = 0 ? */
/* USER ring */
if ((be32_to_cpu(qw1w2) & TM2_QW1W2_VO) &&
(cam == xive_get_field32(TM2_QW1W2_OS_CAM, qw1w2)) &&
@@ -802,6 +814,22 @@ int xive2_presenter_tctx_match(XivePresenter *xptr, XiveTCTX *tctx,
return -1;
}
+bool xive2_tm_irq_precluded(XiveTCTX *tctx, int ring, uint8_t priority)
+{
+ uint8_t *regs = &tctx->regs[ring];
+
+ /*
+ * The xive2_presenter_tctx_match() above tells if there's a match
+ * but for VP-group notification, we still need to look at the
+ * priority to know if the thread can take the interrupt now or if
+ * it is precluded.
+ */
+ if (priority < regs[TM_CPPR]) {
I'm not sure about CPPR and PIPR relationship exactly. Does hardware
set PIPR for pending IPB interrupts even if they are not < CPPR? Or
does it always reflect the presented interrupt
I am not sure. I will dig into the simulation models, and the architecture process flows which they followed, and find out.
According to the TIMA preccess flows and other XIVE2 models, yes,
this should be PIPR. This will be included with group 5:
80 - ppc/xive2: Fix irq preempted by lower priority irq
e76a18f3ab5530f12855bb57d3d4ebecb4532b86
I could include it here but there are there changes that pre-req the change above, in group4 and group 5.
MAK
Thanks,
Nick
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