[tip: x86/irq] x86/irq: Remove bitfields in posted interrupt descriptor

tip-bot2 for Jacob Pan
2024-04-30T13:28:46Z

The following commit has been merged into the x86/irq branch of tip:

Commit-ID: 2254808b53d92c9fe7b645b2f43acc55f22cdce6
Gitweb: https://git.kernel.org/tip/2254808b53d92c9fe7b645b2f43acc55f22cdce6
Author: Jacob Pan <jacob.jun.pan@linux.intel.com>
AuthorDate: Tue, 23 Apr 2024 10:41:05 -07:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Tue, 30 Apr 2024 00:54:42 +02:00

x86/irq: Remove bitfields in posted interrupt descriptor

Mixture of bitfields and types is weird and really not intuitive, remove
bitfields and use typed data exclusively. Bitfields often result in
inferior machine code.

Suggested-by: Sean Christopherson <seanjc@google.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240423174114.526704-4-jacob.jun.pan@linux.intel.com
Link: https://lore.kernel.org/all/20240404101735.402feec8@jacob-builder/T/#mf66e34a82a48f4d8e2926b5581eff59a122de53a
---
arch/x86/include/asm/posted_intr.h | 21 ++++++++++++---------
arch/x86/kvm/vmx/posted_intr.c | 4 ++--
arch/x86/kvm/vmx/vmx.c | 2 +-
3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/posted_intr.h b/arch/x86/include/asm/posted_intr.h
index acf237b..20e3189 100644
--- a/arch/x86/include/asm/posted_intr.h
+++ b/arch/x86/include/asm/posted_intr.h
@@ -15,17 +15,9 @@ struct pi_desc {
};
union {
struct {
- /* bit 256 - Outstanding Notification */
- u16 on : 1,
- /* bit 257 - Suppress Notification */
- sn : 1,
- /* bit 271:258 - Reserved */
- rsvd_1 : 14;
- /* bit 279:272 - Notification Vector */
+ u16 notifications; /* Suppress and outstanding bits */
u8 nv;
- /* bit 287:280 - Reserved */
u8 rsvd_2;
- /* bit 319:288 - Notification Destination */
u32 ndst;
};
u64 control;
@@ -88,4 +80,15 @@ static inline bool pi_test_sn(struct pi_desc *pi_desc)
return test_bit(POSTED_INTR_SN, (unsigned long *)&pi_desc->control);
}

+/* Non-atomic helpers */
+static inline void __pi_set_sn(struct pi_desc *pi_desc)
+{
+ pi_desc->notifications |= BIT(POSTED_INTR_SN);
+}
+
+static inline void __pi_clear_sn(struct pi_desc *pi_desc)
+{
+ pi_desc->notifications &= ~BIT(POSTED_INTR_SN);
+}
+
#endif /* _X86_POSTED_INTR_H */
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index af66231..ec08fa3 100644
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c
@@ -107,7 +107,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
* handle task migration (@cpu != vcpu->cpu).
*/
new.ndst = dest;
- new.sn = 0;
+ __pi_clear_sn(&new);

/*
* Restore the notification vector; in the blocking case, the
@@ -157,7 +157,7 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu)
&per_cpu(wakeup_vcpus_on_cpu, vcpu->cpu));
raw_spin_unlock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu));

- WARN(pi_desc->sn, "PI descriptor SN field set before blocking");
+ WARN(pi_test_sn(pi_desc), "PI descriptor SN field set before blocking");

old.control = READ_ONCE(pi_desc->control);
do {
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 273d264..becefaf 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4845,7 +4845,7 @@ static void __vmx_vcpu_reset(struct kvm_vcpu *vcpu)
* or POSTED_INTR_WAKEUP_VECTOR.
*/
vmx->pi_desc.nv = POSTED_INTR_VECTOR;
- vmx->pi_desc.sn = 1;
+ __pi_set_sn(&vmx->pi_desc);
}

static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)