From: Christoph Hellwig <hch@xxxxxx> Sent: Tuesday, March 1, 2022 2:53 AM > > Power SVM wants to allocate a swiotlb buffer that is not restricted to low memory for > the trusted hypervisor scheme. Consolidate the support for this into the swiotlb_init > interface by adding a new flag. Hyper-V Isolated VMs want to do the same thing of not restricting the swiotlb buffer to low memory. That's what Tianyu Lan's patch set[1] is proposing. Hyper-V synthetic devices have no DMA addressing limitations, and the likelihood of using a PCI pass-thru device with addressing limitations in an Isolated VM seems vanishingly small. So could use of the SWIOTLB_ANY flag be generalized? Let Hyper-V init code set the flag before swiotlb_init() is called. Or provide a CONFIG variable that Hyper-V Isolated VMs could set. Michael [1] https://lore.kernel.org/lkml/20220209122302.213882-1-ltykernel@xxxxxxxxx/ > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > --- > arch/powerpc/include/asm/svm.h | 4 ---- > arch/powerpc/include/asm/swiotlb.h | 1 + > arch/powerpc/kernel/dma-swiotlb.c | 1 + > arch/powerpc/mm/mem.c | 5 +---- > arch/powerpc/platforms/pseries/svm.c | 26 +------------------------- > include/linux/swiotlb.h | 1 + > kernel/dma/swiotlb.c | 9 +++++++-- > 7 files changed, 12 insertions(+), 35 deletions(-) > > diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h > index 7546402d796af..85580b30aba48 100644 > --- a/arch/powerpc/include/asm/svm.h > +++ b/arch/powerpc/include/asm/svm.h > @@ -15,8 +15,6 @@ static inline bool is_secure_guest(void) > return mfmsr() & MSR_S; > } > > -void __init svm_swiotlb_init(void); > - > void dtl_cache_ctor(void *addr); > #define get_dtl_cache_ctor() (is_secure_guest() ? dtl_cache_ctor : NULL) > > @@ -27,8 +25,6 @@ static inline bool is_secure_guest(void) > return false; > } > > -static inline void svm_swiotlb_init(void) {} > - > #define get_dtl_cache_ctor() NULL > > #endif /* CONFIG_PPC_SVM */ > diff --git a/arch/powerpc/include/asm/swiotlb.h > b/arch/powerpc/include/asm/swiotlb.h > index 3c1a1cd161286..4203b5e0a88ed 100644 > --- a/arch/powerpc/include/asm/swiotlb.h > +++ b/arch/powerpc/include/asm/swiotlb.h > @@ -9,6 +9,7 @@ > #include <linux/swiotlb.h> > > extern unsigned int ppc_swiotlb_enable; > +extern unsigned int ppc_swiotlb_flags; > > #ifdef CONFIG_SWIOTLB > void swiotlb_detect_4g(void); > diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma- > swiotlb.c > index fc7816126a401..ba256c37bcc0f 100644 > --- a/arch/powerpc/kernel/dma-swiotlb.c > +++ b/arch/powerpc/kernel/dma-swiotlb.c > @@ -10,6 +10,7 @@ > #include <asm/swiotlb.h> > > unsigned int ppc_swiotlb_enable; > +unsigned int ppc_swiotlb_flags; > > void __init swiotlb_detect_4g(void) > { > diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index > e1519e2edc656..a4d65418c30a9 100644 > --- a/arch/powerpc/mm/mem.c > +++ b/arch/powerpc/mm/mem.c > @@ -249,10 +249,7 @@ void __init mem_init(void) > * back to to-down. > */ > memblock_set_bottom_up(true); > - if (is_secure_guest()) > - svm_swiotlb_init(); > - else > - swiotlb_init(ppc_swiotlb_enable, 0); > + swiotlb_init(ppc_swiotlb_enable, ppc_swiotlb_flags); > #endif > > high_memory = (void *) __va(max_low_pfn * PAGE_SIZE); diff --git > a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c > index c5228f4969eb2..3b4045d508ec8 100644 > --- a/arch/powerpc/platforms/pseries/svm.c > +++ b/arch/powerpc/platforms/pseries/svm.c > @@ -28,7 +28,7 @@ static int __init init_svm(void) > * need to use the SWIOTLB buffer for DMA even if dma_capable() says > * otherwise. > */ > - swiotlb_force = SWIOTLB_FORCE; > + ppc_swiotlb_flags |= SWIOTLB_ANY | SWIOTLB_FORCE; > > /* Share the SWIOTLB buffer with the host. */ > swiotlb_update_mem_attributes(); > @@ -37,30 +37,6 @@ static int __init init_svm(void) } machine_early_initcall(pseries, > init_svm); > > -/* > - * Initialize SWIOTLB. Essentially the same as swiotlb_init(), except that it > - * can allocate the buffer anywhere in memory. Since the hypervisor doesn't have > - * any addressing limitation, we don't need to allocate it in low addresses. > - */ > -void __init svm_swiotlb_init(void) > -{ > - unsigned char *vstart; > - unsigned long bytes, io_tlb_nslabs; > - > - io_tlb_nslabs = (swiotlb_size_or_default() >> IO_TLB_SHIFT); > - io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE); > - > - bytes = io_tlb_nslabs << IO_TLB_SHIFT; > - > - vstart = memblock_alloc(PAGE_ALIGN(bytes), PAGE_SIZE); > - if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, false)) > - return; > - > - > - memblock_free(vstart, PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT)); > - panic("SVM: Cannot allocate SWIOTLB buffer"); > -} > - > int set_memory_encrypted(unsigned long addr, int numpages) { > if (!cc_platform_has(CC_ATTR_MEM_ENCRYPT)) > diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index > dcecf953f7997..ee655f2e4d28b 100644 > --- a/include/linux/swiotlb.h > +++ b/include/linux/swiotlb.h > @@ -15,6 +15,7 @@ struct scatterlist; > > #define SWIOTLB_VERBOSE (1 << 0) /* verbose initialization */ > #define SWIOTLB_FORCE (1 << 1) /* force bounce buffering */ > +#define SWIOTLB_ANY (1 << 2) /* allow any memory for the buffer */ > > /* > * Maximum allowable number of contiguous slabs to map, diff --git > a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 1a40c71c4d51a..77cf73dc20a78 > 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -275,8 +275,13 @@ void __init swiotlb_init(bool addressing_limit, unsigned int > flags) > if (swiotlb_force_disable) > return; > > - /* Get IO TLB memory from the low pages */ > - tlb = memblock_alloc_low(bytes, PAGE_SIZE); > + /* > + * By default allocate the bonuce buffer memory from low memory. > + */ > + if (flags & SWIOTLB_ANY) > + tlb = memblock_alloc(bytes, PAGE_SIZE); > + else > + tlb = memblock_alloc_low(bytes, PAGE_SIZE); > if (!tlb) > goto fail; > if (swiotlb_init_with_tbl(tlb, default_nslabs, flags)) > -- > 2.30.2
