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-rw-r--r--arch/x86/mm/mem_encrypt.c34
1 files changed, 34 insertions, 0 deletions
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 9f27e14e18..c290c55b63 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -12,6 +12,7 @@
#include <linux/swiotlb.h>
#include <linux/cc_platform.h>
#include <linux/mem_encrypt.h>
+#include <linux/virtio_anchor.h>
/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
bool force_dma_unencrypted(struct device *dev)
@@ -86,3 +87,36 @@ void __init mem_encrypt_init(void)
print_mem_encrypt_feature_info();
}
+
+void __init mem_encrypt_setup_arch(void)
+{
+ phys_addr_t total_mem = memblock_phys_mem_size();
+ unsigned long size;
+
+ if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+ return;
+
+ /*
+ * For SEV and TDX, all DMA has to occur via shared/unencrypted pages.
+ * Kernel uses SWIOTLB to make this happen without changing device
+ * drivers. However, depending on the workload being run, the
+ * default 64MB of SWIOTLB may not be enough and SWIOTLB may
+ * run out of buffers for DMA, resulting in I/O errors and/or
+ * performance degradation especially with high I/O workloads.
+ *
+ * Adjust the default size of SWIOTLB using a percentage of guest
+ * memory for SWIOTLB buffers. Also, as the SWIOTLB bounce buffer
+ * memory is allocated from low memory, ensure that the adjusted size
+ * is within the limits of low available memory.
+ *
+ * The percentage of guest memory used here for SWIOTLB buffers
+ * is more of an approximation of the static adjustment which
+ * 64MB for <1G, and ~128M to 256M for 1G-to-4G, i.e., the 6%
+ */
+ size = total_mem * 6 / 100;
+ size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
+ swiotlb_adjust_size(size);
+
+ /* Set restricted memory access for virtio. */
+ virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
+}