From: Christoph Hellwig <hch@xxxxxx> 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@xxxxxx> > --- > 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] > > 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
