linux-kernel - [PATCH RFC v1 3/7] swiotlb-xen: support highmem for xen specific code

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Date:   Wed,  8 Jun 2022 17:55:49 -0700
From:   Dongli Zhang <dongli.zhang@...cle.com>
To:     iommu@...ts.linux-foundation.org, xen-devel@...ts.xenproject.org,
        x86@...nel.org, linuxppc-dev@...ts.ozlabs.org,
        virtualization@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org, hch@...radead.org,
        m.szyprowski@...sung.com, jgross@...e.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        sstabellini@...nel.org, mpe@...erman.id.au, konrad.wilk@...cle.com,
        mst@...hat.com, jasowang@...hat.com, joe.jin@...cle.com
Subject: [PATCH RFC v1 3/7] swiotlb-xen: support highmem for xen specific code

While for most of times the swiotlb-xen relies on the generic swiotlb api
to initialize and use swiotlb, this patch is to support highmem swiotlb
for swiotlb-xen specific code.

E.g., the xen_swiotlb_fixup() may request the hypervisor to provide
64-bit memory pages as swiotlb buffer.

Cc: Konrad Wilk <konrad.wilk@...cle.com>
Cc: Joe Jin <joe.jin@...cle.com>
Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
---
 drivers/xen/swiotlb-xen.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 339f46e21053..d15321e9f9db 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -38,7 +38,8 @@
 #include <asm/dma-mapping.h>
 
 #include <trace/events/swiotlb.h>
-#define MAX_DMA_BITS 32
+#define MAX_DMA32_BITS 32
+#define MAX_DMA64_BITS 64
 
 /*
  * Quick lookup value of the bus address of the IOTLB.
@@ -109,19 +110,25 @@ int xen_swiotlb_fixup(void *buf, unsigned long nslabs, bool high)
 	int rc;
 	unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT);
 	unsigned int i, dma_bits = order + PAGE_SHIFT;
+	unsigned int max_dma_bits = MAX_DMA32_BITS;
 	dma_addr_t dma_handle;
 	phys_addr_t p = virt_to_phys(buf);
 
 	BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1));
 	BUG_ON(nslabs % IO_TLB_SEGSIZE);
 
+	if (high) {
+		dma_bits = MAX_DMA64_BITS;
+		max_dma_bits = MAX_DMA64_BITS;
+	}
+
 	i = 0;
 	do {
 		do {
 			rc = xen_create_contiguous_region(
 				p + (i << IO_TLB_SHIFT), order,
 				dma_bits, &dma_handle);
-		} while (rc && dma_bits++ < MAX_DMA_BITS);
+		} while (rc && dma_bits++ < max_dma_bits);
 		if (rc)
 			return rc;
 
@@ -381,7 +388,8 @@ xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
 static int
 xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
 {
-	return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask;
+	return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask ||
+	       xen_phys_to_dma(hwdev, io_tlb_high_mem.end - 1) <= mask;
 }
 
 const struct dma_map_ops xen_swiotlb_dma_ops = {
-- 
2.17.1