linux-kernel - [RFC V2 36/37] vfio: support dmempage refcount for vfio

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Date:   Mon,  7 Dec 2020 19:31:29 +0800
From:   yulei.kernel@...il.com
To:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        linux-fsdevel@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, naoya.horiguchi@....com,
        viro@...iv.linux.org.uk, pbonzini@...hat.com
Cc:     joao.m.martins@...cle.com, rdunlap@...radead.org,
        sean.j.christopherson@...el.com, xiaoguangrong.eric@...il.com,
        kernellwp@...il.com, lihaiwei.kernel@...il.com,
        Yulei Zhang <yuleixzhang@...cent.com>,
        Chen Zhuo <sagazchen@...cent.com>
Subject: [RFC V2 36/37] vfio: support dmempage refcount for vfio

From: Yulei Zhang <yuleixzhang@...cent.com>

Add get/put_dmem_pfn(), each time when vfio module reference/release
dmempages.

Signed-off-by: Chen Zhuo <sagazchen@...cent.com>
Signed-off-by: Yulei Zhang <yuleixzhang@...cent.com>
---
 drivers/vfio/vfio_iommu_type1.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index c465d1a..4856a89 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -39,6 +39,7 @@
 #include <linux/notifier.h>
 #include <linux/dma-iommu.h>
 #include <linux/irqdomain.h>
+#include <linux/dmem.h>
 
 #define DRIVER_VERSION  "0.2"
 #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@...hat.com>"
@@ -411,7 +412,10 @@ static int put_pfn(unsigned long pfn, int prot)
 
 		unpin_user_pages_dirty_lock(&page, 1, prot & IOMMU_WRITE);
 		return 1;
-	}
+	} else if (is_dmem_pfn(pfn))
+		put_dmem_pfn(pfn);
+
+	/* Dmem page is not counted against user. */
 	return 0;
 }
 
@@ -477,6 +481,9 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 
 		if (!ret && !is_invalid_reserved_pfn(*pfn))
 			ret = -EFAULT;
+
+		if (!ret && is_dmem_pfn(*pfn))
+			get_dmem_pfn(*pfn);
 	}
 done:
 	mmap_read_unlock(mm);
-- 
1.8.3.1