[PATCH v1 1/2] drivers/ehci-dbgp: remove use of run_in_exception_handle()

[dmkhn@xxxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx> 

Polling is relevant for early boot only where facilities requiring
run_in_exception_handler() are not used (e.g. 'd' keyhandler).

Rework ehci_dbgp_poll() by droppping use of run_in_exception_handler().

The ground work for run_in_exception_handler() removal was done under XSA-453:
https://xenbits.xen.org/xsa/advisory-453.html

Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
 xen/drivers/char/ehci-dbgp.c | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/xen/drivers/char/ehci-dbgp.c b/xen/drivers/char/ehci-dbgp.c
index a5c79f56fcf4..ab70e53195eb 100644
--- a/xen/drivers/char/ehci-dbgp.c
+++ b/xen/drivers/char/ehci-dbgp.c
@@ -1245,17 +1245,13 @@ static int cf_check ehci_dbgp_getc(struct serial_port 
*port, char *pc)
     return 1;
 }
 
-/* Safe: ehci_dbgp_poll() runs as timer handler, so not reentrant. */
-static struct serial_port *poll_port;
-
-static void cf_check _ehci_dbgp_poll(const struct cpu_user_regs *regs)
+static void cf_check ehci_dbgp_poll(void *data)
 {
-    struct serial_port *port = poll_port;
+    struct serial_port *port = data;
     struct ehci_dbgp *dbgp = port->uart;
     unsigned long flags;
     unsigned int timeout = MICROSECS(DBGP_CHECK_INTERVAL);
     bool empty = false;
-    const struct cpu_user_regs *old_regs;
 
     if ( !dbgp->ehci_debug )
         return;
@@ -1271,17 +1267,12 @@ static void cf_check _ehci_dbgp_poll(const struct 
cpu_user_regs *regs)
         spin_unlock_irqrestore(&port->tx_lock, flags);
     }
 
-    /* Mimic interrupt context. */
-    old_regs = set_irq_regs(regs);
-
     if ( dbgp->in.chunk )
         serial_rx_interrupt(port);
 
     if ( empty )
         serial_tx_interrupt(port);
 
-    set_irq_regs(old_regs);
-
     if ( spin_trylock_irqsave(&port->tx_lock, flags) )
     {
         if ( dbgp->state == dbgp_idle && !dbgp->in.chunk &&
@@ -1298,12 +1289,6 @@ static void cf_check _ehci_dbgp_poll(const struct 
cpu_user_regs *regs)
     set_timer(&dbgp->timer, NOW() + timeout);
 }
 
-static void cf_check ehci_dbgp_poll(void *data)
-{
-    poll_port = data;
-    run_in_exception_handler(_ehci_dbgp_poll);
-}
-
 static bool ehci_dbgp_setup_preirq(struct ehci_dbgp *dbgp)
 {
     if ( !ehci_dbgp_setup(dbgp) )
-- 
2.34.1