git: 4401b0685163 - main - x86/cpu: introduce an optional hook for early hypervisor initialization

The branch main has been updated by royger:

URL: https://cgit.FreeBSD.org/src/commit/?id=4401b0685163c0a460c1f41b107225b0b0ee2062

commit 4401b0685163c0a460c1f41b107225b0b0ee2062
Author:     Roger Pau Monné <royger@FreeBSD.org>
AuthorDate: 2024-02-02 10:36:52 +0000
Commit:     Roger Pau Monné <royger@FreeBSD.org>
CommitDate: 2024-02-22 10:08:05 +0000

    x86/cpu: introduce an optional hook for early hypervisor initialization
    
    Hypervisor detection is done very early on x86, and so can be used to also do
    some very early hypervisor related initialization.  Such initialization is
    required when running as a Xen PVH guest, as for example the PIT needs to be
    replaced with an hypervisor based timecounter.
    
    Introduce an optional hook that gets called as part of the early hypervisor
    detection.
    
    No functional change intended.
    
    Sponsored by: Cloud Software Group
    Reviewed by: markj kib
    Differential revision: https://reviews.freebsd.org/D43763
---
 sys/x86/x86/identcpu.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sys/x86/x86/identcpu.c b/sys/x86/x86/identcpu.c
index df24c5bddffd..6df138bccba1 100644
--- a/sys/x86/x86/identcpu.c
+++ b/sys/x86/x86/identcpu.c
@@ -1343,6 +1343,7 @@ SYSINIT(hook_tsc_freq, SI_SUB_CONFIGURE, SI_ORDER_ANY, hook_tsc_freq, NULL);
 static struct {
 	const char	*vm_cpuid;
 	int		vm_guest;
+	void		(*init)(void);
 } vm_cpuids[] = {
 	{ "XenVMMXenVMM",	VM_GUEST_XEN },		/* XEN */
 	{ "Microsoft Hv",	VM_GUEST_HV },		/* Microsoft Hyper-V */
@@ -1355,6 +1356,7 @@ static struct {
 static void
 identify_hypervisor_cpuid_base(void)
 {
+	void (*init_fn)(void) = NULL;
 	u_int leaf, regs[4];
 	int i;
 
@@ -1391,6 +1393,7 @@ identify_hypervisor_cpuid_base(void)
 				if (strncmp((const char *)&regs[1],
 				    vm_cpuids[i].vm_cpuid, 12) == 0) {
 					vm_guest = vm_cpuids[i].vm_guest;
+					init_fn = vm_cpuids[i].init;
 					break;
 				}
 
@@ -1423,10 +1426,13 @@ identify_hypervisor_cpuid_base(void)
 				     * preferred.
 				     */
 				    vm_guest != VM_GUEST_HV)
-					return;
+					break;
 			}
 		}
 	}
+
+	if (init_fn != NULL)
+		init_fn();
 }
 
 void