linux-kernel - [PATCH] xen/x86/pvh: Use HVM's flush_tlb

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Date:	Sat, 12 Dec 2015 19:25:55 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	david.vrabel@...rix.com, konrad.wilk@...cle.com
Cc:	xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
	jbeulich@...e.com, Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	stable@...r.kernel.org.#.3.14+
Subject: [PATCH] xen/x86/pvh: Use HVM's flush_tlb_others op

Using MMUEXT_TLB_FLUSH_MULTI doesn't buy us much since the hypervisor
will likely perform same IPIs as would have the guest.

More importantly, using MMUEXT_INVLPG_MULTI may not to invalidate the
guest's address on remote CPU (when, for example, VCPU from another guest
is running there).

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Suggested-by: Jan Beulich <jbeulich@...e.com>
Cc: stable@...r.kernel.org # 3.14+
---
 arch/x86/xen/mmu.c |    9 ++-------
 1 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 9c479fe..9ed7eed 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -2495,14 +2495,9 @@ void __init xen_init_mmu_ops(void)
 {
 	x86_init.paging.pagetable_init = xen_pagetable_init;
 
-	/* Optimization - we can use the HVM one but it has no idea which
-	 * VCPUs are descheduled - which means that it will needlessly IPI
-	 * them. Xen knows so let it do the job.
-	 */
-	if (xen_feature(XENFEAT_auto_translated_physmap)) {
-		pv_mmu_ops.flush_tlb_others = xen_flush_tlb_others;
+	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return;
-	}
+
 	pv_mmu_ops = xen_mmu_ops;
 
 	memset(dummy_mapping, 0xff, PAGE_SIZE);
-- 
1.7.1

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