ppc/xive2: Support "Pull Thread Context to Register" operation

Adds support for single byte read of offset 0x838 of the TIMA address
space.  According to the XIVE2 Specification, this causes the hardware
to atomically:
  1. Read the number of bytes requested (lbz or lhz are supported).
  2. Reset the valid bit of the thread context.
  3. Return the number of bytes requested in step 1 to a register.

Signed-off-by: Glenn Miles <milesg@linux.vnet.ibm.com>
Signed-off-by: Michael Kowal <kowal@linux.ibm.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

hw/intc/xive.c

@@ -179,6 +179,17 @@ static uint64_t xive_tm_pull_pool_ctx(XivePresenter *xptr, XiveTCTX *tctx,
     return qw2w2;
 }
 
+static uint64_t xive_tm_pull_phys_ctx(XivePresenter *xptr, XiveTCTX *tctx,
+                                      hwaddr offset, unsigned size)
+{
+    uint8_t qw3b8_prev = tctx->regs[TM_QW3_HV_PHYS + TM_WORD2];
+    uint8_t qw3b8;
+
+    qw3b8 = qw3b8_prev & ~TM_QW3B8_VT;
+    tctx->regs[TM_QW3_HV_PHYS + TM_WORD2] = qw3b8;
+    return qw3b8;
+}
+
 static void xive_tm_vt_push(XivePresenter *xptr, XiveTCTX *tctx, hwaddr offset,
                             uint64_t value, unsigned size)
 {
@@ -527,6 +538,8 @@ static const XiveTmOp xive_tm_operations[] = {
                                                      xive_tm_pull_pool_ctx },
     { XIVE_TM_HV_PAGE, TM_SPC_PULL_POOL_CTX,      8, NULL,
                                                      xive_tm_pull_pool_ctx },
+    { XIVE_TM_HV_PAGE, TM_SPC_PULL_PHYS_CTX,      1, NULL,
+                                                     xive_tm_pull_phys_ctx },
 };
 
 static const XiveTmOp xive2_tm_operations[] = {
@@ -566,6 +579,8 @@ static const XiveTmOp xive2_tm_operations[] = {
                                                      xive_tm_pull_pool_ctx },
     { XIVE_TM_HV_PAGE, TM_SPC_PULL_OS_CTX_OL,     1, xive2_tm_pull_os_ctx_ol,
                                                      NULL },
+    { XIVE_TM_HV_PAGE, TM_SPC_PULL_PHYS_CTX,      1, NULL,
+                                                     xive_tm_pull_phys_ctx },
 };
 
 static const XiveTmOp *xive_tm_find_op(XivePresenter *xptr, hwaddr offset,

include/hw/ppc/xive_regs.h

@@ -101,6 +101,7 @@
 #define   TM_QW3W2_LP           PPC_BIT32(6)
 #define   TM_QW3W2_LE           PPC_BIT32(7)
 #define   TM_QW3W2_T            PPC_BIT32(31)
+#define   TM_QW3B8_VT           PPC_BIT8(0)
 
 /*
  * In addition to normal loads to "peek" and writes (only when invalid)
@@ -128,6 +129,7 @@
 #define TM_SPC_PULL_POOL_CTX    0x828   /* Load32/Load64 Pull/Invalidate Pool */
                                         /* context to reg                     */
 #define TM_SPC_ACK_HV_REG       0x830   /* Load16 ack HV irq to reg           */
+#define TM_SPC_PULL_PHYS_CTX    0x838   /* Pull phys ctx to reg               */
 #define TM_SPC_PULL_USR_CTX_OL  0xc08   /* Store8 Pull/Inval usr ctx to odd   */
                                         /* line                               */
 #define TM_SPC_ACK_OS_EL        0xc10   /* Store8 ack OS irq to even line     */