[xen staging] serial: fake IRQ-regs context in poll handlers

[patchbot@xxxxxxx]

commit ba3c8373cd67845fd59877959dd3650ec6c557d7
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Feb 22 12:10:38 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Feb 22 12:10:38 2024 +0100

    serial: fake IRQ-regs context in poll handlers
    
    In preparation of dropping the register parameters from
    serial_[rt]x_interrupt() and in turn from IRQ handler functions,
    register state needs making available another way for the few key
    handlers which need it. Fake IRQ-like state.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/drivers/char/ehci-dbgp.c | 6 ++++++
 xen/drivers/char/ns16550.c   | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/xen/drivers/char/ehci-dbgp.c b/xen/drivers/char/ehci-dbgp.c
index bbf4e51c02..1497fe7c84 100644
--- a/xen/drivers/char/ehci-dbgp.c
+++ b/xen/drivers/char/ehci-dbgp.c
@@ -1253,6 +1253,7 @@ static void cf_check _ehci_dbgp_poll(struct cpu_user_regs 
*regs)
     unsigned long flags;
     unsigned int timeout = MICROSECS(DBGP_CHECK_INTERVAL);
     bool empty = false;
+    struct cpu_user_regs *old_regs;
 
     if ( !dbgp->ehci_debug )
         return;
@@ -1268,12 +1269,17 @@ static void cf_check _ehci_dbgp_poll(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, regs);
 
     if ( empty )
         serial_tx_interrupt(port, regs);
 
+    set_irq_regs(old_regs);
+
     if ( spin_trylock_irqsave(&port->tx_lock, flags) )
     {
         if ( dbgp->state == dbgp_idle && !dbgp->in.chunk &&
diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 97bf098534..664d490571 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -211,10 +211,14 @@ static void cf_check __ns16550_poll(struct cpu_user_regs 
*regs)
 {
     struct serial_port *port = this_cpu(poll_port);
     struct ns16550 *uart = port->uart;
+    struct cpu_user_regs *old_regs;
 
     if ( uart->intr_works )
         return; /* Interrupts work - no more polling */
 
+    /* Mimic interrupt context. */
+    old_regs = set_irq_regs(regs);
+
     while ( ns_read_reg(uart, UART_LSR) & UART_LSR_DR )
     {
         if ( ns16550_ioport_invalid(uart) )
@@ -227,6 +231,7 @@ static void cf_check __ns16550_poll(struct cpu_user_regs 
*regs)
         serial_tx_interrupt(port, regs);
 
 out:
+    set_irq_regs(old_regs);
     set_timer(&uart->timer, NOW() + MILLISECS(uart->timeout_ms));
 }
 
--
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