Hello Paolo,

First, I wish you a Happy New Year. Thanks a lot for your patch! I 
patched the RC5 of kernel 6.13 with your patch and KVM HV works! :-)

kvm_hv_final.patch:

virt/kvm/kvm_main.c | 5 +++--
  1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index de2c11dae231..5177e56fdbd5 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c

@@ -2975,10 +2975,11 @@ kvm_pfn_t __kvm_faultin_pfn(const struct 

kvm_memory_slot *slot, gfn_t gfn,
                 .refcounted_page = refcounted_page,
         };

-       if (WARN_ON_ONCE(!writable || !refcounted_page))
+       if (WARN_ON_ONCE(!refcounted_page))
                 return KVM_PFN_ERR_FAULT;

-       *writable = false;
+       if (writable)
+               *writable = false;
         *refcounted_page = NULL;

         return kvm_follow_pfn(&kfp);
---

patch -p0 < kvm_hv_final.patch

patching file a/virt/kvm/kvm_main.c

Now, we have a good patch after 56 test kernels!!!!!!!!!

I will test all QEMU/KVM HV components and report, if they work.

Cheers,
Christian

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