Re: [PATCH v9 01/13] set_memory: add folio_{zap, restore}_direct_map helpers

From: "David Hildenbrand (Red Hat)" <david@kernel.org>
To: kalyazin@amazon.com, Matthew Wilcox <willy@infradead.org>,
	"Kalyazin, Nikita" <kalyazin@amazon.co.uk>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"kvmarm@lists.linux.dev" <kvmarm@lists.linux.dev>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	"linux-kselftest@vger.kernel.org"
	<linux-kselftest@vger.kernel.org>,
	"kernel@xen0n.name" <kernel@xen0n.name>,
	"linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
	"loongarch@lists.linux.dev" <loongarch@lists.linux.dev>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"corbet@lwn.net" <corbet@lwn.net>,
	"maz@kernel.org" <maz@kernel.org>,
	"oupton@kernel.org" <oupton@kernel.org>,
	"joey.gouly@arm.com" <joey.gouly@arm.com>,
	"suzuki.poulose@arm.com" <suzuki.poulose@arm.com>,
	"yuzenghui@huawei.com" <yuzenghui@huawei.com>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	"will@kernel.org" <will@kernel.org>,
	"seanjc@google.com" <seanjc@google.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"luto@kernel.org" <luto@kernel.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"lorenzo.stoakes@oracle.com" <lorenzo.stoakes@oracle.com>,
	"Liam.Howlett@oracle.com" <Liam.Howlett@oracle.com>,
	"vbabka@suse.cz" <vbabka@suse.cz>,
	"rppt@kernel.org" <rppt@kernel.org>,
	"surenb@google.com" <surenb@google.com>,
	"mhocko@suse.com" <mhocko@suse.com>,
	"ast@kernel.org" <ast@kernel.org>,
	"daniel@iogearbox.net" <daniel@iogearbox.net>,
	"andrii@kernel.org" <andrii@kernel.org>,
	"martin.lau@linux.dev" <martin.lau@linux.dev>,
	"eddyz87@gmail.com" <eddyz87@gmail.com>,
	"song@kernel.org" <song@kernel.org>,
	"yonghong.song@linux.dev" <yonghong.song@linux.dev>,
	"john.fastabend@gmail.com" <john.fastabend@gmail.com>,
	"kpsingh@kernel.org" <kpsingh@kernel.org>,
	"sdf@fomichev.me" <sdf@fomichev.me>,
	"haoluo@google.com" <haoluo@google.com>,
	"jolsa@kernel.org" <jolsa@kernel.org>,
	"jgg@ziepe.ca" <jgg@ziepe.ca>,
	"jhubbard@nvidia.com" <jhubbard@nvidia.com>,
	"peterx@redhat.com" <peterx@redhat.com>,
	"jannh@google.com" <jannh@google.com>,
	"pfalcato@suse.de" <pfalcato@suse.de>,
	"shuah@kernel.org" <shuah@kernel.org>,
	"riel@surriel.com" <riel@surriel.com>,
	"ryan.roberts@arm.com" <ryan.roberts@arm.com>,
	"jgross@suse.com" <jgross@suse.com>,
	"yu-cheng.yu@intel.com" <yu-cheng.yu@intel.com>,
	"kas@kernel.org" <kas@kernel.org>,
	"coxu@redhat.com" <coxu@redhat.com>,
	"kevin.brodsky@arm.com" <kevin.brodsky@arm.com>,
	"ackerleytng@google.com" <ackerleytng@google.com>,
	"maobibo@loongson.cn" <maobibo@loongson.cn>,
	"prsampat@amd.com" <prsampat@amd.com>,
	"mlevitsk@redhat.com" <mlevitsk@redhat.com>,
	"jmattson@google.com" <jmattson@google.com>,
	"jthoughton@google.com" <jthoughton@google.com>,
	"agordeev@linux.ibm.com" <agordeev@linux.ibm.com>,
	"alex@ghiti.fr" <alex@ghiti.fr>,
	"aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
	"borntraeger@linux.ibm.com" <borntraeger@linux.ibm.com>,
	"chenhuacai@kernel.org" <chenhuacai@kernel.org>,
	"dev.jain@arm.com" <dev.jain@arm.com>,
	"gor@linux.ibm.com" <gor@linux.ibm.com>,
	"hca@linux.ibm.com" <hca@linux.ibm.com>,
	"Jonathan.Cameron@huawei.com" <Jonathan.Cameron@huawei.com>,
	"palmer@dabbelt.com" <palmer@dabbelt.com>,
	"pjw@kernel.org" <pjw@kernel.org>,
	"shijie@os.amperecomputing.com" <shijie@os.amperecomputing.com>,
	"svens@linux.ibm.com" <svens@linux.ibm.com>,
	"thuth@redhat.com" <thuth@redhat.com>,
	"wyihan@google.com" <wyihan@google.com>,
	"yang@os.amperecomputing.com" <yang@os.amperecomputing.com>,
	"vannapurve@google.com" <vannapurve@google.com>,
	"jackmanb@google.com" <jackmanb@google.com>,
	"aneesh.kumar@kernel.org" <aneesh.kumar@kernel.org>,
	"patrick.roy@linux.dev" <patrick.roy@linux.dev>,
	"Thomson, Jack" <jackabt@amazon.co.uk>,
	"Itazuri, Takahiro" <itazur@amazon.co.uk>,
	"Manwaring, Derek" <derekmn@amazon.com>,
	"Cali, Marco" <xmarcalx@amazon.co.uk>
Subject: Re: [PATCH v9 01/13] set_memory: add folio_{zap, restore}_direct_map helpers
Date: Thu, 15 Jan 2026 21:05:35 +0100	[thread overview]
Message-ID: <2219ec0f-edc4-4267-b251-ee060fd951e2@kernel.org> (raw)
In-Reply-To: <34b246e9-0f7a-4ed6-9e43-845c4238bf41@amazon.com>

On 1/15/26 18:45, Nikita Kalyazin wrote:
> 
> 
> On 15/01/2026 15:55, Matthew Wilcox wrote:
>> On Wed, Jan 14, 2026 at 01:45:23PM +0000, Kalyazin, Nikita wrote:
>>> +int folio_zap_direct_map(struct folio *folio)
>>> +{
>>> +     return set_direct_map_valid_noflush(folio_page(folio, 0),
>>> +                                         folio_nr_pages(folio), false);
>>> +}
>>
>> The implementation isn't the greatest.  None of the implementations
>> of set_direct_map_valid_noflush() actually do anything with the struct
>> page; they all call page_address() or page_to_virt() (fundamentally the
>> same thing).  So converting folio->page->address is a bit inefficient.
>>
>> It feels like we should change set_direct_map_valid_noflush() to take a
>> const void * and pass either page_address() or folio_address(), depending
>> whether the caller has a page or a folio.  What do you think?
> 
> I have nothing against that.  execmem_set_direct_map_valid() appears to
> be the only other user of set_direct_map_valid_noflush() so it isn't
> going to be a broad change.

Makes perfect sense to me :)

-- 
Cheers

David