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Message-ID: <a77609c9c9a09214e38b04133e44eee67fe50ab0.1709635535.git.leon@kernel.org>
Date: Tue,  5 Mar 2024 13:18:32 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Christoph Hellwig <hch@....de>,
	Robin Murphy <robin.murphy@....com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Chaitanya Kulkarni <chaitanyak@...dia.com>
Cc: Leon Romanovsky <leonro@...dia.com>,
	Jonathan Corbet <corbet@....net>,
	Jens Axboe <axboe@...nel.dk>,
	Keith Busch <kbusch@...nel.org>,
	Sagi Grimberg <sagi@...mberg.me>,
	Yishai Hadas <yishaih@...dia.com>,
	Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
	Kevin Tian <kevin.tian@...el.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Jérôme Glisse <jglisse@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org,
	linux-rdma@...r.kernel.org,
	iommu@...ts.linux.dev,
	linux-nvme@...ts.infradead.org,
	kvm@...r.kernel.org,
	linux-mm@...ck.org,
	Bart Van Assche <bvanassche@....org>,
	Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
	Amir Goldstein <amir73il@...il.com>,
	"josef@...icpanda.com" <josef@...icpanda.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	"daniel@...earbox.net" <daniel@...earbox.net>,
	Dan Williams <dan.j.williams@...el.com>,
	"jack@...e.com" <jack@...e.com>,
	Zhu Yanjun <zyjzyj2000@...il.com>
Subject: [RFC RESEND 01/16] mm/hmm: let users to tag specific PFNs

From: Leon Romanovsky <leonro@...dia.com>

Introduce new sticky flag, which isn't overwritten by HMM range fault.
Such flag allows users to tag specific PFNs with extra data in addition
to already filled by HMM.

Signed-off-by: Leon Romanovsky <leonro@...dia.com>
---
 include/linux/hmm.h |  3 +++
 mm/hmm.c            | 34 +++++++++++++++++++++-------------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 126a36571667..b90902baa593 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -23,6 +23,7 @@ struct mmu_interval_notifier;
  * HMM_PFN_WRITE - if the page memory can be written to (requires HMM_PFN_VALID)
  * HMM_PFN_ERROR - accessing the pfn is impossible and the device should
  *                 fail. ie poisoned memory, special pages, no vma, etc
+ * HMM_PFN_STICKY - Flag preserved on input-to-output transformation
  *
  * On input:
  * 0                 - Return the current state of the page, do not fault it.
@@ -36,6 +37,8 @@ enum hmm_pfn_flags {
 	HMM_PFN_VALID = 1UL << (BITS_PER_LONG - 1),
 	HMM_PFN_WRITE = 1UL << (BITS_PER_LONG - 2),
 	HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3),
+	/* Sticky lag, carried from Input to Output */
+	HMM_PFN_STICKY = 1UL << (BITS_PER_LONG - 7),
 	HMM_PFN_ORDER_SHIFT = (BITS_PER_LONG - 8),
 
 	/* Input flags */
diff --git a/mm/hmm.c b/mm/hmm.c
index 277ddcab4947..9645a72beec0 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -44,8 +44,10 @@ static int hmm_pfns_fill(unsigned long addr, unsigned long end,
 {
 	unsigned long i = (addr - range->start) >> PAGE_SHIFT;
 
-	for (; addr < end; addr += PAGE_SIZE, i++)
-		range->hmm_pfns[i] = cpu_flags;
+	for (; addr < end; addr += PAGE_SIZE, i++) {
+		range->hmm_pfns[i] &= HMM_PFN_STICKY;
+		range->hmm_pfns[i] |= cpu_flags;
+	}
 	return 0;
 }
 
@@ -202,8 +204,10 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
 		return hmm_vma_fault(addr, end, required_fault, walk);
 
 	pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
-	for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
-		hmm_pfns[i] = pfn | cpu_flags;
+	for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) {
+		hmm_pfns[i] &= HMM_PFN_STICKY;
+		hmm_pfns[i] |= pfn | cpu_flags;
+	}
 	return 0;
 }
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
@@ -236,7 +240,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 			hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
 		if (required_fault)
 			goto fault;
-		*hmm_pfn = 0;
+		*hmm_pfn = *hmm_pfn & HMM_PFN_STICKY;
 		return 0;
 	}
 
@@ -253,14 +257,14 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 			cpu_flags = HMM_PFN_VALID;
 			if (is_writable_device_private_entry(entry))
 				cpu_flags |= HMM_PFN_WRITE;
-			*hmm_pfn = swp_offset_pfn(entry) | cpu_flags;
+			*hmm_pfn = (*hmm_pfn & HMM_PFN_STICKY) | swp_offset_pfn(entry) | cpu_flags;
 			return 0;
 		}
 
 		required_fault =
 			hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
 		if (!required_fault) {
-			*hmm_pfn = 0;
+			*hmm_pfn = *hmm_pfn & HMM_PFN_STICKY;
 			return 0;
 		}
 
@@ -304,11 +308,11 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 			pte_unmap(ptep);
 			return -EFAULT;
 		}
-		*hmm_pfn = HMM_PFN_ERROR;
+		*hmm_pfn = (*hmm_pfn & HMM_PFN_STICKY) | HMM_PFN_ERROR;
 		return 0;
 	}
 
-	*hmm_pfn = pte_pfn(pte) | cpu_flags;
+	*hmm_pfn = (*hmm_pfn & HMM_PFN_STICKY) | pte_pfn(pte) | cpu_flags;
 	return 0;
 
 fault:
@@ -453,8 +457,10 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 		}
 
 		pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
-		for (i = 0; i < npages; ++i, ++pfn)
-			hmm_pfns[i] = pfn | cpu_flags;
+		for (i = 0; i < npages; ++i, ++pfn) {
+			hmm_pfns[i] &= HMM_PFN_STICKY;
+			hmm_pfns[i] |= pfn | cpu_flags;
+		}
 		goto out_unlock;
 	}
 
@@ -512,8 +518,10 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 	}
 
 	pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
-	for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
-		range->hmm_pfns[i] = pfn | cpu_flags;
+	for (; addr < end; addr += PAGE_SIZE, i++, pfn++) {
+		range->hmm_pfns[i] &= HMM_PFN_STICKY;
+		range->hmm_pfns[i] |= pfn | cpu_flags;
+	}
 
 	spin_unlock(ptl);
 	return 0;
-- 
2.44.0


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