# HG changeset patch
# User yamahata@xxxxxxxxxxxxx
# Node ID 99174e194b6a23795b6006d2c4296f901c567fcb
# Parent  0ac7c4c8ae50a26a7240c4e76e897ae67b52aa69
work around for VT-i performance issues.
vcpu_itr_{i, d}() must flush vTLB according to SDM.
However vTLB flush is very heavy so that it causes severe performance loss.
Considering Linux usage of TRs, epsically dtr[IA64_TR_CURRENT_STACK],
it is safe not to flush vTLB.
vTLB flush in vcpu_itr_{i, d}() is disabled as work around until
good optimization is proposed.
PATCHNAME: disable_vtlb_flush_in_vcpu_itr

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>

diff -r 0ac7c4c8ae50 -r 99174e194b6a xen/arch/ia64/xen/vcpu.c
--- a/xen/arch/ia64/xen/vcpu.c	Wed Jul 12 11:43:35 2006 +0900
+++ b/xen/arch/ia64/xen/vcpu.c	Wed Jul 12 12:02:52 2006 +0900
@@ -1914,12 +1914,25 @@ IA64FAULT vcpu_itr_d(VCPU *vcpu, UINT64 
 	vcpu_set_tr_entry(trp,pte,itir,ifa);
 	vcpu_quick_region_set(PSCBX(vcpu,dtr_regions),ifa);
 
+#if 0
+	//XXX [CORRECTNESS]
+	// vTLB flush is required according to SDM vol2 4.1.1.4 and
+	// table 4-1.
+	//
+	// The following flush is too heavy and it makes
+	// the peformance unaceptably slow. especially when VT-i domain
+	// is created and qemu-dm is busy.
+	// Considering Linux usage of dtr[IA64_TR_CURRENT_STACK],
+	// it's safe not to flush.
+	// Disably the following flush until any good optimization
+	// is proposed.
 	if ((1UL << VHPT_SIZE_LOG2) / sizeof(struct vhpt_lf_entry) <
 	    (1UL << itir_ps(itir)) / PAGE_SIZE)
 		vhpt_flush();
 	else
 		vcpu_flush_tlb_vhpt_range(ifa & itir_mask(itir),
 					  itir_ps(itir));
+#endif
 
 	return IA64_NO_FAULT;
 }
@@ -1938,12 +1951,25 @@ IA64FAULT vcpu_itr_i(VCPU *vcpu, UINT64 
 	vcpu_set_tr_entry(trp,pte,itir,ifa);
 	vcpu_quick_region_set(PSCBX(vcpu,itr_regions),ifa);
 
+#if 0
+	//XXX [CORRECTNESS]
+	// vTLB flush is required according to SDM vol2 4.1.1.4 and
+	// table 4-1.
+	//
+	// The following flush is too heavy and it makes
+	// the peformance unaceptably slow. especially when VT-i domain
+	// is created and qemu-dm is busy.
+	// Considering Linux usage of dtr[IA64_TR_CURRENT_STACK],
+	// it's safe not to flush.
+	// Disably the following flush until any good optimization
+	// is proposed.
 	if ((1UL << VHPT_SIZE_LOG2) / sizeof(struct vhpt_lf_entry) <
 	    (1UL << itir_ps(itir)) / PAGE_SIZE)
 		vhpt_flush();
 	else
 		vcpu_flush_tlb_vhpt_range(ifa & itir_mask(itir),
 					  itir_ps(itir));
+#endif
 
 	return IA64_NO_FAULT;
 }