[PATCH] arm64: swiotlb: Keep the default size for protected guests

[Aneesh Kumar K.V (Arm)]

Realm guests and protected KVM guests may require swiotlb for device DMA
even when all system RAM is addressable by the DMA zones.

Do not reduce the SWIOTLB buffer to the kmalloc-bouncing size for these
guests, as the reduced number of slots can be exhausted during CCA guest
operation.

Fixes: 30c5e45ee2c5 ("dma-direct: make dma_direct_map_phys() honor 
DMA_ATTR_CC_SHARED")
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.ku...@kernel.org>
---
 arch/arm64/mm/init.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index e308a7cabd12..24caaf10e755 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -339,7 +339,8 @@ void __init arch_mm_preinit(void)
 {
        unsigned int flags = SWIOTLB_VERBOSE;
 
-       if (max_pfn <= PFN_DOWN(arm64_dma_phys_limit)) {
+       if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) &&
+           max_pfn <= PFN_DOWN(arm64_dma_phys_limit)) {
                /*
                 * If no bouncing needed for ZONE_DMA, reduce the swiotlb
                 * buffer for kmalloc() bouncing to 1MB per 1GB of RAM.
-- 
2.43.0