linux-kernel - [RFC PATCH QEMU] i386/kvm: Enable paravirtual unused page hint mechanism

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Date:   Mon, 04 Feb 2019 10:19:49 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     rkrcmar@...hat.com, alexander.h.duyck@...ux.intel.com,
        x86@...nel.org, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        pbonzini@...hat.com, tglx@...utronix.de, akpm@...ux-foundation.org
Subject: [RFC PATCH QEMU] i386/kvm: Enable paravirtual unused page hint
 mechanism

From: Alexander Duyck <alexander.h.duyck@...ux.intel.com>

This patch adds the flag named kvm-pv-unused-page-hint. This functionality
is enabled by kvm for x86 and provides a mechanism by which the guest can
indicate to the host which pages it is no longer using. By providing these
hints the guest can help to reduce the memory pressure on the host as
dirtied pages will be cleared and not written out to swap if they are
marked as being unused.

Signed-off-by: Alexander Duyck <alexander.h.duyck@...ux.intel.com>
---
 target/i386/cpu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 2f5412592d30..0d19a9dc64f1 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -900,7 +900,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
             "kvmclock", "kvm-nopiodelay", "kvm-mmu", "kvmclock",
             "kvm-asyncpf", "kvm-steal-time", "kvm-pv-eoi", "kvm-pv-unhalt",
             NULL, "kvm-pv-tlb-flush", NULL, "kvm-pv-ipi",
-            NULL, NULL, NULL, NULL,
+            "kvm-pv-unused-page-hint", NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,
             "kvmclock-stable-bit", NULL, NULL, NULL,