[Resend RFC PATCH V2 09/12] swiotlb: Add bounce buffer remap address setting function

From: Tianyu Lan <ltykernel@gmail.com>
To: kys@microsoft.com, haiyangz@microsoft.com,
	sthemmin@microsoft.com, wei.liu@kernel.org, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
	arnd@arndb.de, akpm@linux-foundation.org,
	gregkh@linuxfoundation.org, konrad.wilk@oracle.com, hch@lst.de,
	m.szyprowski@samsung.com, robin.murphy@arm.com, joro@8bytes.org,
	will@kernel.org, davem@davemloft.net, kuba@kernel.org,
	jejb@linux.ibm.com, martin.petersen@oracle.com
Cc: Tianyu Lan <Tianyu.Lan@microsoft.com>,
	iommu@lists.linux-foundation.org, linux-arch@vger.kernel.org,
	linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, linux-scsi@vger.kernel.org,
	netdev@vger.kernel.org, vkuznets@redhat.com,
	thomas.lendacky@amd.com, brijesh.singh@amd.com,
	sunilmut@microsoft.com
Subject: [Resend RFC PATCH V2 09/12] swiotlb: Add bounce buffer remap address setting function
Date: Wed, 14 Apr 2021 10:49:42 -0400	[thread overview]
Message-ID: <20210414144945.3460554-10-ltykernel@gmail.com> (raw)
In-Reply-To: <20210414144945.3460554-1-ltykernel@gmail.com>

From: Tianyu Lan <Tianyu.Lan@microsoft.com>

For Hyper-V isolation VM with AMD SEV SNP, the bounce buffer(shared memory)
needs to be accessed via extra address space(e.g address above bit39).
Hyper-V code may remap extra address space outside of swiotlb. swiotlb_bounce()
needs to use remap virtual address to copy data from/to bounce buffer. Add
new interface swiotlb_set_bounce_remap() to do that.

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
 include/linux/swiotlb.h |  5 +++++
 kernel/dma/swiotlb.c    | 13 ++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index d9c9fc9ca5d2..3ccd08116683 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -82,8 +82,13 @@ unsigned int swiotlb_max_segment(void);
 size_t swiotlb_max_mapping_size(struct device *dev);
 bool is_swiotlb_active(void);
 void __init swiotlb_adjust_size(unsigned long new_size);
+void swiotlb_set_bounce_remap(unsigned char *vaddr);
 #else
 #define swiotlb_force SWIOTLB_NO_FORCE
+static inline void swiotlb_set_bounce_remap(unsigned char *vaddr)
+{
+}
+
 static inline bool is_swiotlb_buffer(phys_addr_t paddr)
 {
 	return false;
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 7c42df6e6100..5fd2db6aa149 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -94,6 +94,7 @@ static unsigned int io_tlb_index;
  * not be bounced (unless SWIOTLB_FORCE is set).
  */
 static unsigned int max_segment;
+static unsigned char *swiotlb_bounce_remap_addr;
 
 /*
  * We need to save away the original address corresponding to a mapped entry
@@ -421,6 +422,11 @@ void __init swiotlb_exit(void)
 	swiotlb_cleanup();
 }
 
+void swiotlb_set_bounce_remap(unsigned char *vaddr)
+{
+	swiotlb_bounce_remap_addr = vaddr;
+}
+
 /*
  * Bounce: copy the swiotlb buffer from or back to the original dma location
  */
@@ -428,7 +434,12 @@ static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr,
 			   size_t size, enum dma_data_direction dir)
 {
 	unsigned long pfn = PFN_DOWN(orig_addr);
-	unsigned char *vaddr = phys_to_virt(tlb_addr);
+	unsigned char *vaddr;
+
+	if (swiotlb_bounce_remap_addr)
+		vaddr = swiotlb_bounce_remap_addr + tlb_addr - io_tlb_start;
+	else
+		vaddr = phys_to_virt(tlb_addr);
 
 	if (PageHighMem(pfn_to_page(pfn))) {
 		/* The buffer does not have a mapping.  Map it in and copy */
-- 
2.25.1

