Re: [PATCH v2 12/16] xen/riscv: introduce sbi_set_timer()

[Oleksii Kurochko]

On 2/4/26 7:50 AM, Jan Beulich wrote:

On 22.01.2026 17:47, Oleksii Kurochko wrote:

--- a/xen/arch/riscv/include/asm/sbi.h
+++ b/xen/arch/riscv/include/asm/sbi.h
@@ -29,6 +29,10 @@

#define SBI_EXT_BASE 0x10

  #define SBI_EXT_RFENCE                  0x52464E43
+#define SBI_EXT_TIME                    0x54494D45
+
+/* SBI function IDs for TIME extension */
+#define SBI_EXT_TIME_SET_TIMER          0x0

Nit: Do you really mean to have the time extension IDs above ...

  /* SBI function IDs for BASE extension */
  #define SBI_EXT_BASE_GET_SPEC_VERSION   0x0

... the base extension ones?

I will move it after SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA_ASID to be aligned with 
how
extensions are declared.

@@ -134,6 +138,20 @@ int sbi_remote_hfence_gvma(const cpumask_t *cpu_mask, 
vaddr_t start,
  int sbi_remote_hfence_gvma_vmid(const cpumask_t *cpu_mask, vaddr_t start,
                                  size_t size, unsigned long vmid);

+/*

+ * Programs the clock for next event after stime_value time. This function also
+ * clears the pending timer interrupt bit.
+ * If the supervisor wishes to clear the timer interrupt without scheduling the
+ * next timer event, it can either request a timer interrupt infinitely far
+ * into the future (i.e., (uint64_t)-1), or it can instead mask the timer
+ * interrupt by clearing sie.STIE CSR bit.
+ * The stime_value parameter represents absolute time measured in ticks.
+ *
+ * This SBI call returns 0 upon success or an implementation specific negative
+ * error code.
+ */
+extern int (*sbi_set_timer)(uint64_t stime_value);

__read_mostly or even __ro_after_init?

I will add __ro_after_init to be in sync with sbi_rfence.

@@ -326,6 +358,14 @@ int __init sbi_init(void)
              sbi_rfence = sbi_rfence_v02;
              printk("SBI v0.2 RFENCE extension detected\n");
          }
+
+        if ( sbi_probe_extension(SBI_EXT_TIME) > 0 )
+        {
+            sbi_set_timer = sbi_set_timer_v02;
+            printk("SBI v0.2 TIME extension detected\n");

Is this really relevant to log especially in release builds? IOW can this at
least be downgraded to dprintk()?

Probably not, it could be useful for debugging to understand what kind and 
version
of extension is used. I am okay with using of dprintk().

Thanks.

~ Oleksii