Re: [PATCH v19 091/130] KVM: TDX: remove use of struct vcpu_vmx from posted_interrupt.c

[Binbin Wu <binbin.wu@linux.intel.com>]

On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> As TDX will use posted_interrupt.c, the use of struct vcpu_vmx is a
> blocker.  Because the members of

Extra "of"

> struct pi_desc pi_desc and struct
> list_head pi_wakeup_list are only used in posted_interrupt.c, introduce
> common structure, struct vcpu_pi, make vcpu_vmx and vcpu_tdx has same
> layout in the top of structure.
>
> To minimize the diff size, avoid code conversion like,
> vmx->pi_desc => vmx->common->pi_desc.  Instead add compile time check
> if the layout is expected.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
>   arch/x86/kvm/vmx/posted_intr.c | 41 ++++++++++++++++++++++++++--------
>   arch/x86/kvm/vmx/posted_intr.h | 11 +++++++++
>   arch/x86/kvm/vmx/tdx.c         |  1 +
>   arch/x86/kvm/vmx/tdx.h         |  8 +++++++
>   arch/x86/kvm/vmx/vmx.h         | 14 +++++++-----
>   5 files changed, 60 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
> index af662312fd07..b66add9da0f3 100644
> --- a/arch/x86/kvm/vmx/posted_intr.c
> +++ b/arch/x86/kvm/vmx/posted_intr.c
> @@ -11,6 +11,7 @@
>   #include "posted_intr.h"
>   #include "trace.h"
>   #include "vmx.h"
> +#include "tdx.h"
>   
>   /*
>    * Maintain a per-CPU list of vCPUs that need to be awakened by wakeup_handler()
> @@ -31,9 +32,29 @@ static DEFINE_PER_CPU(struct list_head, wakeup_vcpus_on_cpu);
>    */
>   static DEFINE_PER_CPU(raw_spinlock_t, wakeup_vcpus_on_cpu_lock);
>   
> +/*
> + * The layout of the head of struct vcpu_vmx and struct vcpu_tdx must match with
> + * struct vcpu_pi.
> + */
> +static_assert(offsetof(struct vcpu_pi, pi_desc) ==
> +	      offsetof(struct vcpu_vmx, pi_desc));
> +static_assert(offsetof(struct vcpu_pi, pi_wakeup_list) ==
> +	      offsetof(struct vcpu_vmx, pi_wakeup_list));
> +#ifdef CONFIG_INTEL_TDX_HOST
> +static_assert(offsetof(struct vcpu_pi, pi_desc) ==
> +	      offsetof(struct vcpu_tdx, pi_desc));
> +static_assert(offsetof(struct vcpu_pi, pi_wakeup_list) ==
> +	      offsetof(struct vcpu_tdx, pi_wakeup_list));
> +#endif
> +
> +static inline struct vcpu_pi *vcpu_to_pi(struct kvm_vcpu *vcpu)
> +{
> +	return (struct vcpu_pi *)vcpu;
> +}
> +
>   static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu)
>   {
> -	return &(to_vmx(vcpu)->pi_desc);
> +	return &vcpu_to_pi(vcpu)->pi_desc;
>   }
>   
>   static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new)
> @@ -52,8 +73,8 @@ static int pi_try_set_control(struct pi_desc *pi_desc, u64 *pold, u64 new)
>   
>   void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
>   {
> -	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
> -	struct vcpu_vmx *vmx = to_vmx(vcpu);
> +	struct vcpu_pi *vcpu_pi = vcpu_to_pi(vcpu);
> +	struct pi_desc *pi_desc = &vcpu_pi->pi_desc;
>   	struct pi_desc old, new;
>   	unsigned long flags;
>   	unsigned int dest;
> @@ -90,7 +111,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
>   	 */
>   	if (pi_desc->nv == POSTED_INTR_WAKEUP_VECTOR) {
>   		raw_spin_lock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu));
> -		list_del(&vmx->pi_wakeup_list);
> +		list_del(&vcpu_pi->pi_wakeup_list);
>   		raw_spin_unlock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu));
>   	}
>   
> @@ -145,15 +166,15 @@ static bool vmx_can_use_vtd_pi(struct kvm *kvm)
>    */
>   static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu)
>   {
> -	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
> -	struct vcpu_vmx *vmx = to_vmx(vcpu);
> +	struct vcpu_pi *vcpu_pi = vcpu_to_pi(vcpu);
> +	struct pi_desc *pi_desc = &vcpu_pi->pi_desc;
>   	struct pi_desc old, new;
>   	unsigned long flags;
>   
>   	local_irq_save(flags);
>   
>   	raw_spin_lock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu));
> -	list_add_tail(&vmx->pi_wakeup_list,
> +	list_add_tail(&vcpu_pi->pi_wakeup_list,
>   		      &per_cpu(wakeup_vcpus_on_cpu, vcpu->cpu));
>   	raw_spin_unlock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu));
>   
> @@ -190,7 +211,8 @@ static bool vmx_needs_pi_wakeup(struct kvm_vcpu *vcpu)
>   	 * notification vector is switched to the one that calls
>   	 * back to the pi_wakeup_handler() function.
>   	 */
> -	return vmx_can_use_ipiv(vcpu) || vmx_can_use_vtd_pi(vcpu->kvm);
> +	return (vmx_can_use_ipiv(vcpu) && !is_td_vcpu(vcpu)) ||
> +		vmx_can_use_vtd_pi(vcpu->kvm);
>   }
>   
>   void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu)
> @@ -200,7 +222,8 @@ void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu)
>   	if (!vmx_needs_pi_wakeup(vcpu))
>   		return;
>   
> -	if (kvm_vcpu_is_blocking(vcpu) && !vmx_interrupt_blocked(vcpu))
> +	if (kvm_vcpu_is_blocking(vcpu) &&
> +	    (is_td_vcpu(vcpu) || !vmx_interrupt_blocked(vcpu)))
>   		pi_enable_wakeup_handler(vcpu);
>   
>   	/*
> diff --git a/arch/x86/kvm/vmx/posted_intr.h b/arch/x86/kvm/vmx/posted_intr.h
> index 26992076552e..2fe8222308b2 100644
> --- a/arch/x86/kvm/vmx/posted_intr.h
> +++ b/arch/x86/kvm/vmx/posted_intr.h
> @@ -94,6 +94,17 @@ static inline bool pi_test_sn(struct pi_desc *pi_desc)
>   			(unsigned long *)&pi_desc->control);
>   }
>   
> +struct vcpu_pi {
> +	struct kvm_vcpu	vcpu;
> +
> +	/* Posted interrupt descriptor */
> +	struct pi_desc pi_desc;
> +
> +	/* Used if this vCPU is waiting for PI notification wakeup. */
> +	struct list_head pi_wakeup_list;
> +	/* Until here common layout betwwn vcpu_vmx and vcpu_tdx. */

s/betwwn/between

Also, in pi_wakeup_handler(), it is still using struct vcpu_vmx, but it 
could
be vcpu_tdx.
Functionally it is OK, however, since you have added vcpu_pi, should it use
vcpu_pi instead of vcpu_vmx in pi_wakeup_handler()?

> +};
> +
>   void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu);
>   void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu);
>   void pi_wakeup_handler(void);
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index a5b52aa6d153..1da58c36217c 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -584,6 +584,7 @@ int tdx_vcpu_create(struct kvm_vcpu *vcpu)
>   
>   	fpstate_set_confidential(&vcpu->arch.guest_fpu);
>   	vcpu->arch.apic->guest_apic_protected = true;
> +	INIT_LIST_HEAD(&tdx->pi_wakeup_list);
>   
>   	vcpu->arch.efer = EFER_SCE | EFER_LME | EFER_LMA | EFER_NX;
>   
> diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> index 7f8c78f06508..eaffa7384725 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -4,6 +4,7 @@
>   
>   #ifdef CONFIG_INTEL_TDX_HOST
>   
> +#include "posted_intr.h"
>   #include "pmu_intel.h"
>   #include "tdx_ops.h"
>   
> @@ -69,6 +70,13 @@ union tdx_exit_reason {
>   struct vcpu_tdx {
>   	struct kvm_vcpu	vcpu;
>   
> +	/* Posted interrupt descriptor */
> +	struct pi_desc pi_desc;
> +
> +	/* Used if this vCPU is waiting for PI notification wakeup. */
> +	struct list_head pi_wakeup_list;
> +	/* Until here same layout to struct vcpu_pi. */
> +
>   	unsigned long tdvpr_pa;
>   	unsigned long *tdvpx_pa;
>   	bool td_vcpu_created;
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 79ff54f08fee..634a9a250b95 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -235,6 +235,14 @@ struct nested_vmx {
>   
>   struct vcpu_vmx {
>   	struct kvm_vcpu       vcpu;
> +
> +	/* Posted interrupt descriptor */
> +	struct pi_desc pi_desc;
> +
> +	/* Used if this vCPU is waiting for PI notification wakeup. */
> +	struct list_head pi_wakeup_list;
> +	/* Until here same layout to struct vcpu_pi. */
> +
>   	u8                    fail;
>   	u8		      x2apic_msr_bitmap_mode;
>   
> @@ -304,12 +312,6 @@ struct vcpu_vmx {
>   
>   	union vmx_exit_reason exit_reason;
>   
> -	/* Posted interrupt descriptor */
> -	struct pi_desc pi_desc;
> -
> -	/* Used if this vCPU is waiting for PI notification wakeup. */
> -	struct list_head pi_wakeup_list;
> -
>   	/* Support for a guest hypervisor (nested VMX) */
>   	struct nested_vmx nested;
>