RE: [PATCH 08/11] swiotlb: make the swiotlb_init interface more useful
From: Michael Kelley (LINUX) <hidden>
Date: 2022-02-28 03:09:44
Also in:
linux-arm-kernel, linux-hyperv, linux-iommu, linux-mips, linux-pci, linux-riscv, linux-s390, xen-devel
From: Christoph Hellwig <hch@lst.de> Sent: Sunday, February 27, 2022 6:31 AM
Pass a bool to pass if swiotlb needs to be enabled based on the addressing needs and replace the verbose argument with a set of flags, including one to force enable bounce buffering. Note that this patch removes the possibility to force xen-swiotlb use using swiotlb=force on the command line on x86 (arm and arm64 never supported that), but this interface will be restored shortly. Signed-off-by: Christoph Hellwig <hch@lst.de> --- arch/arm/mm/init.c | 6 +---- arch/arm64/mm/init.c | 6 +---- arch/ia64/mm/init.c | 4 +-- arch/mips/cavium-octeon/dma-octeon.c | 2 +- arch/mips/loongson64/dma.c | 2 +- arch/mips/sibyte/common/dma.c | 2 +- arch/powerpc/include/asm/swiotlb.h | 1 + arch/powerpc/mm/mem.c | 3 ++- arch/powerpc/platforms/pseries/setup.c | 3 --- arch/riscv/mm/init.c | 8 +----- arch/s390/mm/init.c | 3 +-- arch/x86/kernel/cpu/mshyperv.c | 8 ------ arch/x86/kernel/pci-dma.c | 15 ++++++----- arch/x86/mm/mem_encrypt_amd.c | 3 --- drivers/xen/swiotlb-xen.c | 4 +-- include/linux/swiotlb.h | 15 ++++++----- include/trace/events/swiotlb.h | 29 ++++++++------------- kernel/dma/swiotlb.c | 35 ++++++++++++++------------ 18 files changed, 56 insertions(+), 93 deletions(-)
[snip]
quoted hunk ↗ jump to hunk
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 5a99f993e6392..568274917f1cd 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c@@ -336,14 +336,6 @@ static void __init ms_hyperv_init_platform(void) swiotlb_unencrypted_base = ms_hyperv.shared_gpa_boundary; #endif } - -#ifdef CONFIG_SWIOTLB - /* - * Enable swiotlb force mode in Isolation VM to - * use swiotlb bounce buffer for dma transaction. - */ - swiotlb_force = SWIOTLB_FORCE; -#endif
With this code removed, it's not clear to me what forces the use of the swiotlb in a Hyper-V isolated VM. The code in pci_swiotlb_detect_4g() doesn't catch this case because cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT) returns "false" in a Hyper-V guest. In the Hyper-V guest, it's only cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) that returns "true". I'm looking more closely at the meaning of the CC_ATTR_* values, and it may be that Hyper-V should also return "true" for CC_ATTR_MEM_ENCRYPT, but I don't think CC_ATTR_HOST_MEM_ENCRYPT should return "true". Michael