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spf=pass smtp.mailfrom=arm.com; dmarc=pass action=none header.from=arm.com; dkim=pass header.d=arm.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=armh.onmicrosoft.com; s=selector2-armh-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=fndaDEo2QfTLg4yPXyoHD4mZ+VaKn/RmwZSeipwhK1s=; b=WrjBfAnjlzTfNEjR0Q/c2HeQ6qeUaPC6gp2yvFBEdiInfVYoUkmyK5Ur2cbNECv2qB+YNkimhCcbUa4tUykAna7akfflNooP0tlA9a3eG3G/GL7gwlR/7vG7iq4Ekm2cV4BuQ0VSDtgr9QHRyBrlbiCa6Ql5ApsqIf8B/XB0yR4= From: Bertrand Marquis To: Julien Grall CC: "xen-devel@lists.xenproject.org" , Julien Grall , Stefano Stabellini , Volodymyr Babchuk Subject: Re: [PATCH for-next] xen/arm: mm: flush_page_to_ram() only need to clean to PoC Thread-Topic: [PATCH for-next] xen/arm: mm: flush_page_to_ram() only need to clean to PoC Thread-Index: AQHXB7GCcUtPYwKMVk+6z4A6IyPFF6pkFLEA Date: Mon, 22 Feb 2021 11:58:33 +0000 Message-ID: References: <20210220175413.14640-1-julien@xen.org> In-Reply-To: <20210220175413.14640-1-julien@xen.org> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3608.120.23.2.4) Authentication-Results-Original: xen.org; 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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Feb 2021 11:58:41.4495 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 7d7d4aa5-d91d-41c8-0e8e-08d8d729329e X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: VE1EUR03FT051.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0802MB2281 Hi Julien, > On 20 Feb 2021, at 17:54, Julien Grall wrote: >=20 > From: Julien Grall >=20 > At the moment, flush_page_to_ram() is both cleaning and invalidate to > PoC the page. However, the cache line can be speculated and pull in the > cache right after as it is part of the direct map. If we go further through this logic maybe all calls to clean_and_invalidate_dcache_va_range could be transformed in a clean_dcache_va_range. >=20 > So it is pointless to try to invalidate the line in the data cache. >=20 But what about processors which would not speculate ? Do you expect any performance optimization here ? If so it might be good to explain it as I am not quite sure I get it. Cheers Bertrand > Signed-off-by: Julien Grall > --- > xen/arch/arm/mm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c > index 59f8a3f15fd1..2f11d214e184 100644 > --- a/xen/arch/arm/mm.c > +++ b/xen/arch/arm/mm.c > @@ -529,7 +529,7 @@ void flush_page_to_ram(unsigned long mfn, bool sync_i= cache) > { > void *v =3D map_domain_page(_mfn(mfn)); >=20 > - clean_and_invalidate_dcache_va_range(v, PAGE_SIZE); > + clean_dcache_va_range(v, PAGE_SIZE); > unmap_domain_page(v); >=20 > /* > --=20 > 2.17.1 >=20 >=20