2022-06-09 01:04:00

by Dongli Zhang

Subject: [PATCH RFC v1 6/7] virtio: use io_tlb_high_mem if it is active

When the swiotlb is enforced (e.g., when amd sev is involved), the virito
driver will not be able to use 4+ GB memory. Therefore, the virtio driver
uses 'io_tlb_high_mem' as swiotlb.

Cc: Konrad Wilk <[email protected]>
Cc: Joe Jin <[email protected]>
Signed-off-by: Dongli Zhang <[email protected]>
---
drivers/virtio/virtio.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index ef04a96942bf..d9ebe3940e2d 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -5,6 +5,8 @@
#include <linux/module.h>
#include <linux/idr.h>
#include <linux/of.h>
+#include <linux/swiotlb.h>
+#include <linux/dma-mapping.h>
#include <uapi/linux/virtio_ids.h>

/* Unique numbering for virtio devices. */
@@ -241,6 +243,12 @@ static int virtio_dev_probe(struct device *_d)
u64 device_features;
u64 driver_features;
u64 driver_features_legacy;
+ struct device *parent = dev->dev.parent;
+ u64 dma_mask = min_not_zero(*parent->dma_mask,
+ parent->bus_dma_limit);
+
+ if (dma_mask == DMA_BIT_MASK(64))
+ swiotlb_use_high(parent);

/* We have a driver! */
virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
--
2.17.1

2022-06-09 05:41:07

by Christoph Hellwig

Subject: Re: [PATCH RFC v1 6/7] virtio: use io_tlb_high_mem if it is active

On Wed, Jun 08, 2022 at 05:55:52PM -0700, Dongli Zhang wrote:
> /* Unique numbering for virtio devices. */
> @@ -241,6 +243,12 @@ static int virtio_dev_probe(struct device *_d)
> u64 device_features;
> u64 driver_features;
> u64 driver_features_legacy;
> + struct device *parent = dev->dev.parent;
> + u64 dma_mask = min_not_zero(*parent->dma_mask,
> + parent->bus_dma_limit);
> +
> + if (dma_mask == DMA_BIT_MASK(64))
> + swiotlb_use_high(parent);

The driver already very clearly communicated its addressing
requirements. The underlying swiotlb code needs to transparently
pick the right pool.