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Re: [PATCH v5 1/3] xen/x86: add nmi continuation framework



On 12.11.20 14:41, Jan Beulich wrote:
On 12.11.2020 14:14, Juergen Gross wrote:
--- a/xen/arch/x86/genapic/x2apic.c
+++ b/xen/arch/x86/genapic/x2apic.c
@@ -89,6 +89,7 @@ static unsigned int cpu_mask_to_apicid_x2apic_cluster(const 
cpumask_t *cpumask)
static void send_IPI_self_x2apic(uint8_t vector)
  {
+    /* NMI continuation handling relies on using a shorthand here. */
      apic_wrmsr(APIC_SELF_IPI, vector);
  }

I'm inclined to drop this hunk again - I did ask for ...

--- a/xen/arch/x86/smp.c
+++ b/xen/arch/x86/smp.c
@@ -163,6 +163,7 @@ void send_IPI_self(int vector)
void send_IPI_self_legacy(uint8_t vector)
  {
+    /* NMI continuation handling relies on using a shorthand here. */
      send_IPI_shortcut(APIC_DEST_SELF, vector, APIC_DEST_PHYSICAL);
  }

... this one only simply because x2APIC doesn't have the same restriction.

It would still be bad if the x2APIC variant would e.g. use
send_IPI_mask_x2apic_cluster() due to its usage of
per_cpu(scratch_mask).

Juergen

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