[Xen-changelog] [xen master] xen/arm: p2m: Rework the context switch to another VTTBR in flush_tlb_domain

[patchbot@xxxxxxx]

commit 69d8e2e0cfb987e6461818695d211d10841a7281
Author:     Julien Grall <julien.grall@xxxxxxx>
AuthorDate: Thu Jul 28 15:20:16 2016 +0100
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Thu Jul 28 17:42:40 2016 -0700

    xen/arm: p2m: Rework the context switch to another VTTBR in flush_tlb_domain
    
    The current implementation of flush_tlb_domain is relying on the domain
    to have a single p2m. With the upcoming feature altp2m, a single domain
    may have different p2m. So we would need to switch to the correct p2m in
    order to flush the TLBs.
    
    Rather than checking whether the domain is not the current domain, check
    whether the VTTBR is different. The resulting assembly code is much
    smaller: from 38 instructions (+ 2 functions call) to 22 instructions.
    
    Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
    Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/arm/p2m.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index aff5906..7ee0171 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -151,24 +151,28 @@ void p2m_restore_state(struct vcpu *n)
 
 void flush_tlb_domain(struct domain *d)
 {
+    struct p2m_domain *p2m = &d->arch.p2m;
     unsigned long flags = 0;
+    uint64_t ovttbr;
 
     /*
-     * Update the VTTBR if necessary with the domain d. In this case,
-     * it's only necessary to flush TLBs on every CPUs with the current VMID
-     * (our domain).
+     * ARM only provides an instruction to flush TLBs for the current
+     * VMID. So switch to the VTTBR of a given P2M if different.
      */
-    if ( d != current->domain )
+    ovttbr = READ_SYSREG64(VTTBR_EL2);
+    if ( ovttbr != p2m->vttbr )
     {
         local_irq_save(flags);
-        p2m_load_VTTBR(d);
+        WRITE_SYSREG64(p2m->vttbr, VTTBR_EL2);
+        isb();
     }
 
     flush_tlb();
 
-    if ( d != current->domain )
+    if ( ovttbr != READ_SYSREG64(VTTBR_EL2) )
     {
-        p2m_load_VTTBR(current->domain);
+        WRITE_SYSREG64(ovttbr, VTTBR_EL2);
+        isb();
         local_irq_restore(flags);
     }
 }
--
generated by git-patchbot for /home/xen/git/xen.git#master

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