Re: [PATCH v10 5/5] x86/hyperv: Change interrupt vector for nested root partition

[Wei Liu <wei.liu@kernel.org>]

On Mon, Jan 02, 2023 at 07:12:55AM +0000, Jinank Jain wrote:
> Traditionally we have been using the HYPERVISOR_CALLBACK_VECTOR to relay
> the VMBus interrupt. But this does not work in case of nested
> hypervisor. Microsoft Hypervisor reserves 0x31 to 0x34 as the interrupt
> vector range for VMBus and thus we have to use one of the vectors from
> that range and setup the IDT accordingly.
> 
> Signed-off-by: Jinank Jain <jinankjain@linux.microsoft.com>

I've applied all but this patch to hyperv-next.

This patch still needs an ack or nack from x86 maintainers to proceed.

Thanks,
Wei.

> ---
>  arch/x86/include/asm/idtentry.h    |  2 ++
>  arch/x86/include/asm/irq_vectors.h |  6 ++++++
>  arch/x86/kernel/cpu/mshyperv.c     | 15 +++++++++++++++
>  arch/x86/kernel/idt.c              | 10 ++++++++++
>  drivers/hv/vmbus_drv.c             |  3 ++-
>  5 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
> index 72184b0b2219..c0648e3e4d4a 100644
> --- a/arch/x86/include/asm/idtentry.h
> +++ b/arch/x86/include/asm/idtentry.h
> @@ -686,6 +686,8 @@ DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_NESTED_VECTOR,	sysvec_kvm_posted_intr_nested
>  DECLARE_IDTENTRY_SYSVEC(HYPERVISOR_CALLBACK_VECTOR,	sysvec_hyperv_callback);
>  DECLARE_IDTENTRY_SYSVEC(HYPERV_REENLIGHTENMENT_VECTOR,	sysvec_hyperv_reenlightenment);
>  DECLARE_IDTENTRY_SYSVEC(HYPERV_STIMER0_VECTOR,	sysvec_hyperv_stimer0);
> +DECLARE_IDTENTRY_SYSVEC(HYPERV_INTR_NESTED_VMBUS_VECTOR,
> +			sysvec_hyperv_nested_vmbus_intr);
>  #endif
>  
>  #if IS_ENABLED(CONFIG_ACRN_GUEST)
> diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
> index 43dcb9284208..729d19eab7f5 100644
> --- a/arch/x86/include/asm/irq_vectors.h
> +++ b/arch/x86/include/asm/irq_vectors.h
> @@ -102,6 +102,12 @@
>  #if IS_ENABLED(CONFIG_HYPERV)
>  #define HYPERV_REENLIGHTENMENT_VECTOR	0xee
>  #define HYPERV_STIMER0_VECTOR		0xed
> +/*
> + * FIXME: Change this, once Microsoft Hypervisor changes its assumption
> + * around VMBus interrupt vector allocation for nested root partition.
> + * Or provides a better interface to detect this instead of hardcoding.
> + */
> +#define HYPERV_INTR_NESTED_VMBUS_VECTOR	0x31
>  #endif
>  
>  #define LOCAL_TIMER_VECTOR		0xec
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 938fc82edf05..4dfe0f9d7be3 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -126,6 +126,21 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback)
>  	set_irq_regs(old_regs);
>  }
>  
> +DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_nested_vmbus_intr)
> +{
> +	struct pt_regs *old_regs = set_irq_regs(regs);
> +
> +	inc_irq_stat(irq_hv_callback_count);
> +
> +	if (vmbus_handler)
> +		vmbus_handler();
> +
> +	if (ms_hyperv.hints & HV_DEPRECATING_AEOI_RECOMMENDED)
> +		ack_APIC_irq();
> +
> +	set_irq_regs(old_regs);
> +}
> +
>  void hv_setup_vmbus_handler(void (*handler)(void))
>  {
>  	vmbus_handler = handler;
> diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
> index a58c6bc1cd68..3536935cea39 100644
> --- a/arch/x86/kernel/idt.c
> +++ b/arch/x86/kernel/idt.c
> @@ -160,6 +160,16 @@ static const __initconst struct idt_data apic_idts[] = {
>  # endif
>  	INTG(SPURIOUS_APIC_VECTOR,		asm_sysvec_spurious_apic_interrupt),
>  	INTG(ERROR_APIC_VECTOR,			asm_sysvec_error_interrupt),
> +#ifdef CONFIG_HYPERV
> +	/*
> +	 * This is a hack because we cannot install this interrupt handler
> +	 * via alloc_intr_gate as it does not allow interrupt vector less
> +	 * than FIRST_SYSTEM_VECTORS. And hyperv does not want anything other
> +	 * than 0x31-0x34 as the interrupt vector for vmbus interrupt in case
> +	 * of nested setup.
> +	 */
> +	INTG(HYPERV_INTR_NESTED_VMBUS_VECTOR, asm_sysvec_hyperv_nested_vmbus_intr),
> +#endif
>  #endif
>  };
>  
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 6324e01d5eec..740878367426 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -2768,7 +2768,8 @@ static int __init hv_acpi_init(void)
>  	 * normal Linux IRQ mechanism is not used in this case.
>  	 */
>  #ifdef HYPERVISOR_CALLBACK_VECTOR
> -	vmbus_interrupt = HYPERVISOR_CALLBACK_VECTOR;
> +	vmbus_interrupt = hv_nested ? HYPERV_INTR_NESTED_VMBUS_VECTOR :
> +				      HYPERVISOR_CALLBACK_VECTOR;
>  	vmbus_irq = -1;
>  #endif
>  
> -- 
> 2.25.1
>