Re: [PATCH] x86/svm: mandatory update VMCB nextrip for soft interrupts

Teddy Astie <[email protected]> Thu, 6 Aug 2026 11:31:53 +0200

Newsgroups	gmane.comp.emulators.xen.devel
Message-ID	<1786008715.8631fc262581453bbf619ec5b2062170.19fd66a3fd5000e099@vates.tech>

Le 06/08/2026 à 05:17, Chunjie Zhu a écrit :
> Signed-off-by: Chunjie Zhu <[email protected]>
> ---
>   xen/arch/x86/hvm/svm/nestedsvm.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/hvm/svm/nestedsvm.c b/xen/arch/x86/hvm/svm/nestedsvm.c
> index b06124c2c9ed..815713b8b506 100644
> --- a/xen/arch/x86/hvm/svm/nestedsvm.c
> +++ b/xen/arch/x86/hvm/svm/nestedsvm.c
> @@ -449,7 +449,14 @@ static int nsvm_vmcb_prepare4vmrun(struct vcpu *v, struct cpu_user_regs *regs)
>       n2vmcb->virt_ext.bytes =
>           n1vmcb->virt_ext.bytes | ns_vmcb->virt_ext.bytes;
>   
> -    /* NextRIP - only evaluated on #VMEXIT. */
> +    /* next_rip is consumed on VMRUN as the return address pushed on the
> +     * stack·for·injected·soft·exceptions/interrupts. This assignment
> +     * statement must be enforced, otherwise, it might cause vcpu wedge.
> +     *

Well, it's more that nrip semantics requires nrip to be properly 
configured in the vmcb. That looks like a missing piece, but we may 
still want to keep some informations about what happens on the #VMEXIT side.

> +     * APM Vol.2 Event Injection does not specifies what happens if NEXTRIP
> +     * holds an invalid/garbage value.

To me, it's similar to setting RIP directly to a bogus value. nrip is 
just a "next instruction rip" basically (wrt event injection, ...).

> +     */
> +    n2vmcb->nextrip = ns_vmcb->nextrip;
>   
>       /*
>        * VMCB Save State Area

Teddy

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