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[209.85.220.65]) by mx.google.com with SMTPS id s68sor2400856pfk.40.2019.02.04.15.00.22 for (Google Transport Security); Mon, 04 Feb 2019 15:00:22 -0800 (PST) Received-SPF: pass (google.com: domain of nadav.amit@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=GnZmV+ME; spf=pass (google.com: domain of nadav.amit@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=nadav.amit@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=kH0IHrJSoQFyAx4iofM5iGBNHAzEokQMp3CgcnSLWMU=; b=GnZmV+MEm33hkAkY9eB1nN1X3/jXo/QLCfEDhSJHU8vzSX1HEogQumQfMPy7HPxobt T+aXfqW8AFccomMTEPS6w8U7z/QcF3pLVNJ5o18VlhjMLaxIW4hh67KUXdGfX2hld2uA YbgK+lOK7MkPlmhe9On64hl1wtmvQgt0A0xOrTP/WOPA6U9ShU++WofSNfFfldPvhRGp GkI4vrJ3suckIBPSHSiBgWqfUVn5DMulWpeEuhs/SwVOx2HF8HkjtrCBKyZ3CFLyZBoJ PjDVle8X6etbJLIULNived/+VwIgGz9z/NiXGw8mInO8NvfUxIlnbP5tdVMg0ZnSPW76 /cvA== X-Google-Smtp-Source: AHgI3IbxieJuU8CAP3+p4ZFwdqqvo1bB729g6OoR3vk4fJ4zW7+3UdY/IEHwMwKmNkmuVu4fxAp8ZA== X-Received: by 2002:a62:cf02:: with SMTP id b2mr1802977pfg.183.1549321221419; Mon, 04 Feb 2019 15:00:21 -0800 (PST) Received: from [10.33.115.182] ([66.170.99.1]) by smtp.gmail.com with ESMTPSA id u70sm1579632pfa.176.2019.02.04.15.00.19 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 04 Feb 2019 15:00:20 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 12.2 \(3445.102.3\)) Subject: Re: [RFC PATCH 3/4] kvm: Add guest side support for free memory hints From: Nadav Amit In-Reply-To: <20190204181552.12095.46287.stgit@localhost.localdomain> Date: Mon, 4 Feb 2019 15:00:18 -0800 Cc: Linux-MM , LKML , kvm list , Radim Krcmar , Alexander Duyck , X86 ML , Ingo Molnar , bp@alien8.de, hpa@zytor.com, pbonzini@redhat.com, tglx@linutronix.de, akpm@linux-foundation.org Content-Transfer-Encoding: quoted-printable Message-Id: <4E64E8CA-6741-47DF-87DE-88D01B01B15D@gmail.com> References: <20190204181118.12095.38300.stgit@localhost.localdomain> <20190204181552.12095.46287.stgit@localhost.localdomain> To: Alexander Duyck X-Mailer: Apple Mail (2.3445.102.3) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Feb 4, 2019, at 10:15 AM, Alexander Duyck = wrote: >=20 > From: Alexander Duyck >=20 > Add guest support for providing free memory hints to the KVM = hypervisor for > freed pages huge TLB size or larger. I am restricting the size to > huge TLB order and larger because the hypercalls are too expensive to = be > performing one per 4K page. Using the huge TLB order became the = obvious > choice for the order to use as it allows us to avoid fragmentation of = higher > order memory on the host. >=20 > I have limited the functionality so that it doesn't work when page > poisoning is enabled. I did this because a write to the page after = doing an > MADV_DONTNEED would effectively negate the hint, so it would be = wasting > cycles to do so. >=20 > Signed-off-by: Alexander Duyck > --- > arch/x86/include/asm/page.h | 13 +++++++++++++ > arch/x86/kernel/kvm.c | 23 +++++++++++++++++++++++ > 2 files changed, 36 insertions(+) >=20 > diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h > index 7555b48803a8..4487ad7a3385 100644 > --- a/arch/x86/include/asm/page.h > +++ b/arch/x86/include/asm/page.h > @@ -18,6 +18,19 @@ >=20 > struct page; >=20 > +#ifdef CONFIG_KVM_GUEST > +#include > +extern struct static_key_false pv_free_page_hint_enabled; > + > +#define HAVE_ARCH_FREE_PAGE > +void __arch_free_page(struct page *page, unsigned int order); > +static inline void arch_free_page(struct page *page, unsigned int = order) > +{ > + if (static_branch_unlikely(&pv_free_page_hint_enabled)) > + __arch_free_page(page, order); > +} > +#endif This patch and the following one assume that only KVM should be able to = hook to these events. I do not think it is appropriate for __arch_free_page() = to effectively mean =E2=80=9Ckvm_guest_free_page()=E2=80=9D. Is it possible to use the paravirt infrastructure for this feature, similarly to other PV features? It is not the best infrastructure, but = at least it is hypervisor-neutral.