Commit fbf979a0 authored Oct 17, 2024 by Steven Price Committed by Catalin Marinas Oct 23, 2024

arm64: Enforce bounce buffers for realm DMA



Within a realm guest it's not possible for a device emulated by the VMM
to access arbitrary guest memory. So force the use of bounce buffers to
ensure that the memory the emulated devices are accessing is in memory
which is explicitly shared with the host.

This adds a call to swiotlb_update_mem_attributes() which calls
set_memory_decrypted() to ensure the bounce buffer memory is shared with
the host. For non-realm guests or hosts this is a no-op.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20241017131434.40935-8-steven.price@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 491db21d

arch/arm64/kernel/rsi.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -6,6 +6,7 @@
		#include <linux/jump_label.h>
		#include <linux/memblock.h>
		#include <linux/psci.h>
		#include <linux/swiotlb.h>

		#include <asm/io.h>
		#include <asm/rsi.h>

arch/arm64/mm/init.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -41,6 +41,7 @@
		#include <asm/kvm_host.h>
		#include <asm/memory.h>
		#include <asm/numa.h>
		#include <asm/rsi.h>
		#include <asm/sections.h>
		#include <asm/setup.h>
		#include <linux/sizes.h>
		@@ -366,8 +367,14 @@ void __init bootmem_init(void)
		*/
		void __init mem_init(void)
		{
		unsigned int flags = SWIOTLB_VERBOSE;
		bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);

		if (is_realm_world()) {
		swiotlb = true;
		flags \|= SWIOTLB_FORCE;
		}

		if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb) {
		/*
		* If no bouncing needed for ZONE_DMA, reduce the swiotlb
		@@ -379,7 +386,8 @@ void __init mem_init(void)
		swiotlb = true;
		}

		swiotlb_init(swiotlb, SWIOTLB_VERBOSE);
		swiotlb_init(swiotlb, flags);
		swiotlb_update_mem_attributes();

		/* this will put all unused low memory onto the freelists */
		memblock_free_all();