[RFC PATCH 2/7] common: Track latest pCPU that ran the vCPU

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

Track on which pCPU each vCPU of a domain ran. This will
be used to know whether a TLB flush is required or not
when the vCPU is migrated on another pCPU.

Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
---
I wonder if there is a way to move 

    curr->domain->latest_vcpu[cpu] = curr->vcpu_id

into a (at least more) common code ?

 xen/arch/x86/hvm/svm/svm.c | 3 +++
 xen/arch/x86/hvm/vmx/vmx.c | 3 +++
 xen/common/domain.c        | 8 ++++++++
 xen/include/xen/sched.h    | 4 ++++
 4 files changed, 18 insertions(+)

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index ced6166847..58e927ae04 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -967,6 +967,7 @@ void asmlinkage svm_vmenter_helper(void)
     const struct cpu_user_regs *regs = guest_cpu_user_regs();
     struct vcpu *curr = current;
     struct vmcb_struct *vmcb = curr->arch.hvm.svm.vmcb;
+    unsigned int cpu = smp_processor_id();
 
     ASSERT(hvmemul_cache_disabled(curr));
 
@@ -977,6 +978,8 @@ void asmlinkage svm_vmenter_helper(void)
 
     svm_sync_vmcb(curr, vmcb_needs_vmsave);
 
+    curr->domain->latest_vcpu[cpu] = curr->vcpu_id;
+
     vmcb->rax = regs->rax;
     vmcb->rip = regs->rip;
     vmcb->rsp = regs->rsp;
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 269ca56433..ec0a790336 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -4934,6 +4934,7 @@ bool asmlinkage vmx_vmenter_helper(const struct 
cpu_user_regs *regs)
     u32 new_asid, old_asid;
     struct hvm_vcpu_asid *p_asid;
     bool need_flush;
+    unsigned int cpu = smp_processor_id();
 
     ASSERT(hvmemul_cache_disabled(curr));
 
@@ -4977,6 +4978,8 @@ bool asmlinkage vmx_vmenter_helper(const struct 
cpu_user_regs *regs)
     if ( unlikely(need_flush) )
         vpid_sync_all();
 
+    currd->latest_vcpu[cpu] = curr->vcpu_id;
+
     if ( paging_mode_hap(curr->domain) )
     {
         struct ept_data *ept = &p2m_get_hostp2m(currd)->ept;
diff --git a/xen/common/domain.c b/xen/common/domain.c
index bb9e210c28..7867166411 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -758,6 +758,7 @@ static void _domain_destroy(struct domain *d)
     rangeset_domain_destroy(d);
 
     free_cpumask_var(d->dirty_cpumask);
+    xfree(d->latest_vcpu);
 
     xsm_free_security_domain(d);
 
@@ -992,6 +993,13 @@ struct domain *domain_create(domid_t domid,
     if ( !zalloc_cpumask_var(&d->dirty_cpumask) )
         goto fail;
 
+    err = -ENOMEM;
+    d->latest_vcpu = xmalloc_array(int, nr_cpu_ids);
+    if ( !d->latest_vcpu )
+        goto fail;
+    for (unsigned int i = 0; i < nr_cpu_ids; i++)
+        d->latest_vcpu[i] = -1;
+
     rangeset_domain_initialise(d);
 
     if ( is_idle_domain(d) )
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 212c7d765c..4b8ae21b51 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -567,6 +567,10 @@ struct domain
     /* Bitmask of CPUs which are holding onto this domain's state. */
     cpumask_var_t    dirty_cpumask;
 
+    /* Mapping of the latest vCPU that ran on a specific CPU
+     * (-1 if the vCPU hasn't ran yet) */
+    int *latest_vcpu;
+
     struct arch_domain arch;
 
     void *ssid; /* sHype security subject identifier */
-- 
2.52.0



--
Teddy Astie | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech