[xen staging] x86/HPET: don't arbitrarily cap delta in reprogram_hpet_evt_channel()

[patchbot@xxxxxxx]

commit 5eedd1fa1dbdbda9304824955582ca38464dd911
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Jan 22 14:14:02 2026 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jan 22 16:06:22 2026 +0100

    x86/HPET: don't arbitrarily cap delta in reprogram_hpet_evt_channel()
    
    There's no reason to set an arbitrary upper bound of 10 seconds. We can
    simply set the comparator such that it'll take a whole cycle through all
    32-bit values until the next interrupt would be raised. (For an extremely
    fast-running HPET [400 MHz and up] 10 seconds would also be too long.)
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/hpet.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hpet.c b/xen/arch/x86/hpet.c
index 722a69ab13..1ea8ae4574 100644
--- a/xen/arch/x86/hpet.c
+++ b/xen/arch/x86/hpet.c
@@ -23,7 +23,6 @@
 #include <asm/irq-vectors.h>
 #include <asm/msi.h>
 
-#define MAX_DELTA_NS MILLISECS(10*1000)
 #define MIN_DELTA_NS MICROSECS(20)
 
 #define HPET_EVT_USED_BIT    0
@@ -164,10 +163,15 @@ static int reprogram_hpet_evt_channel(
 
     ASSERT(expire != STIME_MAX);
 
-    delta = min_t(int64_t, delta, MAX_DELTA_NS);
     delta = max_t(int64_t, delta, MIN_DELTA_NS);
     delta = ns2ticks(delta, ch->shift, ch->mult);
 
+    if ( delta > UINT32_MAX )
+    {
+        hpet_write32(hpet_read32(HPET_COUNTER), HPET_Tn_CMP(ch->idx));
+        return 0;
+    }
+
     do {
         ret = hpet_next_event(delta, ch->idx);
         delta += delta;
--
generated by git-patchbot for /home/xen/git/xen.git#staging