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Fri, 5 Jun 2020 21:40:01 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userp3020.oracle.com with ESMTP id 31f927ra3d-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 05 Jun 2020 21:40:01 +0000 Received: from abhmp0010.oracle.com (abhmp0010.oracle.com [141.146.116.16]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 055LdwSK029799; Fri, 5 Jun 2020 21:39:58 GMT Received: from [10.39.238.70] (/10.39.238.70) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 05 Jun 2020 14:39:58 -0700 Subject: Re: [PATCH 03/12] x86/xen: Introduce new function to map HYPERVISOR_shared_info on Resume To: Anchal Agarwal Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, jgross@suse.com, linux-pm@vger.kernel.org, linux-mm@kvack.org, kamatam@amazon.com, sstabellini@kernel.org, konrad.wilk@oracle.com, roger.pau@citrix.com, axboe@kernel.dk, davem@davemloft.net, rjw@rjwysocki.net, len.brown@intel.com, pavel@ucw.cz, peterz@infradead.org, eduval@amazon.com, sblbir@amazon.com, xen-devel@lists.xenproject.org, vkuznets@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dwmw@amazon.co.uk, benh@kernel.crashing.org References: <529f544a64bb93b920bf86b1d3f86d93b0a4219b.1589926004.git.anchalag@amazon.com> <72989b50-0c13-7a2b-19e2-de4a3646c83f@oracle.com> <20200604230307.GB25251@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> From: Boris Ostrovsky Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200604230307.GB25251@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9643 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 phishscore=0 mlxlogscore=999 bulkscore=0 suspectscore=0 adultscore=0 malwarescore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006050159 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9643 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 clxscore=1015 impostorscore=0 adultscore=0 priorityscore=1501 mlxlogscore=999 mlxscore=0 bulkscore=0 lowpriorityscore=0 cotscore=-2147483648 phishscore=0 spamscore=0 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006050159 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/4/20 7:03 PM, Anchal Agarwal wrote: > On Sat, May 30, 2020 at 07:02:01PM -0400, Boris Ostrovsky wrote: >> CAUTION: This email originated from outside of the organization. Do no= t click links or open attachments unless you can confirm the sender and k= now the content is safe. >> >> >> >> On 5/19/20 7:25 PM, Anchal Agarwal wrote: >>> Introduce a small function which re-uses shared page's PA allocated >>> during guest initialization time in reserve_shared_info() and not >>> allocate new page during resume flow. >>> It also does the mapping of shared_info_page by calling >>> xen_hvm_init_shared_info() to use the function. >>> >>> Signed-off-by: Anchal Agarwal >>> --- >>> arch/x86/xen/enlighten_hvm.c | 7 +++++++ >>> arch/x86/xen/xen-ops.h | 1 + >>> 2 files changed, 8 insertions(+) >>> >>> diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hv= m.c >>> index e138f7de52d2..75b1ec7a0fcd 100644 >>> --- a/arch/x86/xen/enlighten_hvm.c >>> +++ b/arch/x86/xen/enlighten_hvm.c >>> @@ -27,6 +27,13 @@ >>> >>> static unsigned long shared_info_pfn; >>> >>> +void xen_hvm_map_shared_info(void) >>> +{ >>> + xen_hvm_init_shared_info(); >>> + if (shared_info_pfn) >>> + HYPERVISOR_shared_info =3D __va(PFN_PHYS(shared_info_pf= n)); >>> +} >>> + >> >> AFAICT it is only called once so I don't see a need for new routine. >> >> > HYPERVISOR_shared_info can only be mapped in this scope without refacto= ring > much of the code. Refactoring what? All am suggesting is --- a/arch/x86/xen/suspend.c +++ b/arch/x86/xen/suspend.c @@ -124,7 +124,9 @@ static void xen_syscore_resume(void) =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 return; =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* No need to setup vcpu_info = as it's already moved off */ -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 xen_hvm_map_shared_info(); +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 xen_hvm_init_shared_info(); +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (shared_info_pfn) +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0 HYPERVISOR_shared_info =3D __va(PFN_PHYS(shared_info_pfn)); =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pvclock_resume(); >> And is it possible for shared_info_pfn to be NULL in resume path (whic= h >> is where this is called)? >> >> > I don't think it should be, still a sanity check but I don't think its = needed there > because hibernation will fail in any case if thats the case.=20 If shared_info_pfn is NULL you'd have problems long before hibernation started. We set it in xen_hvm_guest_init() and never touch again. In fact, I'd argue that it should be __ro_after_init. > However, HYPERVISOR_shared_info does needs to be re-mapped on resume as= its been > marked to dummy address on suspend. Its also safe in case va changes. > Does the answer your question? I wasn't arguing whether HYPERVISOR_shared_info needs to be set, I was only saying that shared_info_pfn doesn't need to be tested. -boris