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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707397415; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pIlP7oM0EEqilPcmLZnP6SsQWOUafm3zOC4xNfXOlAk=; b=sNzLutvjXvtrpuaEQYIBLgMGyNKDP7I68KagK50m7unhoXfxvRXjf9nyHv0xkMvdYukqUs Htw6hryr+q0Sf5oDqNpTuYOMJ9DeQS3D34KUXhEOR0WV18dS9pqwedVKdAWr/yTJUe2qc0 EP4OvoXSdo7HkP7DY5AHDloxmFE4LHw= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BCFD0DA7; Thu, 8 Feb 2024 05:04:16 -0800 (PST) Received: from arm.com (RQ4T19M611.cambridge.arm.com [10.1.31.53]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9EEA93F5A1; Thu, 8 Feb 2024 05:03:29 -0800 (PST) Date: Thu, 8 Feb 2024 13:03:27 +0000 From: Catalin Marinas To: ankita@nvidia.com Cc: jgg@nvidia.com, maz@kernel.org, oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, reinette.chatre@intel.com, surenb@google.com, stefanha@redhat.com, brauner@kernel.org, will@kernel.org, mark.rutland@arm.com, alex.williamson@redhat.com, kevin.tian@intel.com, yi.l.liu@intel.com, ardb@kernel.org, akpm@linux-foundation.org, andreyknvl@gmail.com, wangjinchao@xfusion.com, gshan@redhat.com, ricarkol@google.com, linux-mm@kvack.org, lpieralisi@kernel.org, rananta@google.com, ryan.roberts@arm.com, aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, kvmarm@lists.linux.dev, mochs@nvidia.com, zhiw@nvidia.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, David Hildenbrand Subject: Re: [PATCH v6 2/4] mm: introduce new flag to indicate wc safe Message-ID: References: <20240207204652.22954-1-ankita@nvidia.com> <20240207204652.22954-3-ankita@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240207204652.22954-3-ankita@nvidia.com> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 73402A0016 X-Stat-Signature: ut6qj5eqp4kt47nn98pqp5x5mfgz4a6m X-HE-Tag: 1707397415-905801 X-HE-Meta: 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 5p3gBrLM umTXOyZRCWJNUiMyCrobhUrTcSHVHSBuIGahiv6PN++zMJnBBx1df9s6LyxnYt6TkYqcYh/jo0z8/ffkvmBplnaHTS3GZUI4OKfTwCVrgXWw+ZG8CCQqlahzIlWRLyi5vAWyq 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: List-Subscribe: List-Unsubscribe: On Thu, Feb 08, 2024 at 02:16:50AM +0530, ankita@nvidia.com wrote: > diff --git a/include/linux/mm.h b/include/linux/mm.h > index f5a97dec5169..884c068a79eb 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -391,6 +391,20 @@ extern unsigned int kobjsize(const void *objp); > # define VM_UFFD_MINOR VM_NONE > #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */ > > +/* > + * This flag is used to connect VFIO to arch specific KVM code. It > + * indicates that the memory under this VMA is safe for use with any > + * non-cachable memory type inside KVM. Some VFIO devices, on some > + * platforms, are thought to be unsafe and can cause machine crashes if > + * KVM does not lock down the memory type. > + */ > +#ifdef CONFIG_64BIT > +#define VM_VFIO_ALLOW_WC_BIT 39 > +#define VM_VFIO_ALLOW_WC BIT(VM_VFIO_ALLOW_WC_BIT) > +#else > +#define VM_VFIO_ALLOW_WC VM_NONE > +#endif Adding David Hildenbrand to this thread as well since we briefly discussed potential alternatives (not sure we came to any conclusion). -- Catalin