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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 15C271C000A X-Stat-Signature: u47fpi1rakt3hpp4oqbhzt5a1ey6sh6f X-HE-Tag: 1745872676-272337 X-HE-Meta: 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 lYr4zghz i8PQEN9Tf0qmTEFjoSSGARDWsO33YEtjpS7qZtgGp+gGSTJSJKAyK9W+axqRZqnibaSMFYHNyvr+9ze0NYqr4U33fTYacMtQyYT51VleyByVm9WcvsaxKgCBME+l19gYBquBBaJ2EUeknVkYfNVKxHqRcxEefgIa8xLdJZ59TLIiplSoci5/xrtz33pfEaDDr7i1nQ34hfPkGHtCNghvPnns4x7g2CJTeiJbeOl2UUHOleOtAJZrtcGSN0VgrhGgctzo8aaRp+dgovfgZ3j0kpIdIaGjq4cJQ5Tu67BFwbS/+2CoPpdiKOu6nG/Wv/A0Q4v3OiNObvNprYm/6P/4KuEbJVwI+sMtB6hhTQ1ualpNLa3kkO6/fd6nE41edbY0z75WtnrMfrJyuGq5Pudfh6ET+0A1Zt02ZfCs8wkfXM/8W8kI/S0AVAzvl5hNkJ8JpSZpavVC/IoIScprVLIuWzd1E8ydlyYs9xC6E 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 28.04.25 18:21, Peter Xu wrote: > On Mon, Apr 28, 2025 at 04:58:46PM +0200, David Hildenbrand wrote: >> >>>> What it does on PAT (only implementation so far ...) is looking up the >>>> memory type to select the caching mode that can be use. >>>> >>>> "sanitize" was IMHO a good fit, because we must make sure that we don't use >>>> the wrong caching mode. >>>> >>>> update/setup/... don't make that quite clear. Any other suggestions? >>> >>> I'm very poor on naming.. :( So far anything seems slightly better than >>> sanitize to me, as the word "sanitize" is actually also used in memtype.c >>> for other purpose.. see sanitize_phys(). >> >> Sure, one can sanitize a lot of things. Here it's the cachemode/pgrpot, in >> the other functions it's an address. >> >> Likely we should just call it pfnmap_X_cachemode()/ >> >> Set/update don't really fit for X in case pfnmap_X_cachemode() is a NOP. >> >> pfnmap_setup_cachemode() ? Hm. > > Sounds good here. Okay, I'll use that one. If ever something else besides PAT would require different semantics, they can bother with finding a better name :) > >> >>> >>>> >>>>> >>>>>> + * @pfn: the start of the pfn range >>>>>> + * @size: the size of the pfn range >>>>>> + * @prot: the pgprot to sanitize >>>>>> + * >>>>>> + * Sanitize the given pgprot for a pfn range, for example, adjusting the >>>>>> + * cachemode. >>>>>> + * >>>>>> + * This function cannot fail for a single page, but can fail for multiple >>>>>> + * pages. >>>>>> + * >>>>>> + * Returns 0 on success and -EINVAL on error. >>>>>> + */ >>>>>> +int pfnmap_sanitize_pgprot(unsigned long pfn, unsigned long size, >>>>>> + pgprot_t *prot); >>>>>> extern int track_pfn_copy(struct vm_area_struct *dst_vma, >>>>>> struct vm_area_struct *src_vma, unsigned long *pfn); >>>>>> extern void untrack_pfn_copy(struct vm_area_struct *dst_vma, >>>>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>>>> index fdcf0a6049b9f..b8ae5e1493315 100644 >>>>>> --- a/mm/huge_memory.c >>>>>> +++ b/mm/huge_memory.c >>>>>> @@ -1455,7 +1455,9 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write) >>>>>> return VM_FAULT_OOM; >>>>>> } >>>>>> - track_pfn_insert(vma, &pgprot, pfn); >>>>>> + if (pfnmap_sanitize_pgprot(pfn_t_to_pfn(pfn), PAGE_SIZE, &pgprot)) >>>>>> + return VM_FAULT_FALLBACK; >>>>> >>>>> Would "pgtable" leak if it fails? If it's PAGE_SIZE, IIUC it won't ever >>>>> trigger, though. >>>>> >>>>> Maybe we could have a "void pfnmap_sanitize_pgprot_pfn(&pgprot, pfn)" to >>>>> replace track_pfn_insert() and never fail? Dropping vma ref is definitely >>>>> a win already in all cases. >>>> >>>> It could be a simple wrapper around pfnmap_sanitize_pgprot(), yes. That's >>>> certainly helpful for the single-page case. >>>> >>>> Regarding never failing here: we should check the whole range. We have to >>>> make sure that none of the pages has a memory type / caching mode that is >>>> incompatible with what we setup. >>> >>> Would it happen in real world? >>>> IIUC per-vma registration needs to happen first, which checks for >> memtype >>> conflicts in the first place, or reserve_pfn_range() could already have >>> failed. >>>> Here it's the fault path looking up the memtype, so I would expect it is >>> guaranteed all pfns under the same vma is following the verified (and same) >>> memtype? >> >> The whole point of track_pfn_insert() is that it is used when we *don't* use >> reserve_pfn_range()->track_pfn_remap(), no? >> >> track_pfn_remap() would check the whole range that gets mapped, so >> track_pfn_insert() user must similarly check the whole range that gets >> mapped. >> >> Note that even track_pfn_insert() is already pretty clear on the intended >> usage: "called when a _new_ single pfn is established" > > We need to define "new" then.. But I agree it's not crystal clear at > least. I think I just wasn't the first to assume it was reserved, see this > (especially, the "Expectation" part..): > > commit 5180da410db6369d1f95c9014da1c9bc33fb043e > Author: Suresh Siddha > Date: Mon Oct 8 16:28:29 2012 -0700 > > x86, pat: separate the pfn attribute tracking for remap_pfn_range and vm_insert_pfn > > With PAT enabled, vm_insert_pfn() looks up the existing pfn memory > attribute and uses it. Expectation is that the driver reserves the > memory attributes for the pfn before calling vm_insert_pfn(). It's all confusing. We do have the following functions relevant in pat code: (1) memtype_reserve(): used by ioremap and set_memory_XX (2) memtype_reserve_io(): used by iomap (3) reserve_pfn_range(): only remap_pfn_range() calls it (4) arch_io_reserve_memtype_wc() Which one would perform the reservation for, say, vfio? I agree that if there would be a guarantee/expectation that all PFNs have the same memtype (from previous reservation), it would be sufficient to check a single PFN, and we could document that. I just don't easily see where that reservation is happening. So a pointer to that would be appreciated! -- Cheers, David / dhildenb