On Thursday, November 5, 2020, Ashish Kalra <[email protected]> wrote:
> From: Ashish Kalra <[email protected]> > > For SEV, all DMA to and from guest has to use shared > (un-encrypted) pages. SEV uses SWIOTLB to make this > happen without requiring changes to device drivers. > However, depending on workload being run, the default > 64MB of SWIOTLB might not be enough and SWIOTLB > may run out of buffers to use for DMA, resulting > in I/O errors and/or performance degradation for > high I/O workloads. > > Increase the default size of SWIOTLB for SEV guests > using a minimum value of 128MB and a maximum value > of 512MB, determining on amount of provisioned guest > memory. > > Using late_initcall() interface to invoke > swiotlb_adjust() does not work as the size > adjustment needs to be done before mem_encrypt_init() > and reserve_crashkernel() which use the allocated > SWIOTLB buffer size, hence calling it explicitly > from setup_arch(). > > The SWIOTLB default size adjustment is added as an > architecture specific interface/callback to allow > architectures such as those supporting memory > encryption to adjust/expand SWIOTLB size for their > use. > > Signed-off-by: Ashish Kalra <[email protected]> > --- > arch/x86/kernel/setup.c | 2 ++ > arch/x86/mm/mem_encrypt.c | 42 +++++++++++++++++++++++++++++++++++++++ > include/linux/swiotlb.h | 1 + > kernel/dma/swiotlb.c | 27 +++++++++++++++++++++++++ > 4 files changed, 72 insertions(+) > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index 3511736fbc74..b073d58dd4a3 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -1166,6 +1166,8 @@ void __init setup_arch(char **cmdline_p) > if (boot_cpu_has(X86_FEATURE_GBPAGES)) > hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT); > > + swiotlb_adjust(); > + > /* > * Reserve memory for crash kernel after SRAT is parsed so that it > * won't consume hotpluggable memory. > diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c > index 3f248f0d0e07..e0deb157cddd 100644 > --- a/arch/x86/mm/mem_encrypt.c > +++ b/arch/x86/mm/mem_encrypt.c > @@ -489,7 +489,49 @@ static void print_mem_encrypt_feature_info(void) > pr_cont("\n"); > } > > +#define TOTAL_MEM_1G 0x40000000UL > +#define TOTAL_MEM_4G 0x100000000UL > + > +#define SIZE_128M (128UL<<20) > +#define SIZE_256M (256UL<<20) > +#define SIZE_512M (512UL<<20) We have these constants defined in sizes.h. > + > /* Architecture __weak replacement functions */ > +unsigned long __init arch_swiotlb_adjust(unsigned long iotlb_default_size) > +{ > + unsigned long size = 0; > + > + /* > + * For SEV, all DMA has to occur via shared/unencrypted pages. > + * SEV uses SWOTLB to make this happen without changing device > + * drivers. However, depending on the workload being run, the > + * default 64MB of SWIOTLB may not be enough & SWIOTLB may > + * run out of buffers for DMA, resulting in I/O errors and/or > + * performance degradation especially with high I/O workloads. > + * Increase the default size of SWIOTLB for SEV guests using > + * a minimum value of 128MB and a maximum value of 512MB, > + * depending on amount of provisioned guest memory. > + */ > + if (sev_active()) { > + phys_addr_t total_mem = memblock_phys_mem_size(); > + > + if (total_mem <= TOTAL_MEM_1G) > + size = clamp(iotlb_default_size * 2, SIZE_128M, > + SIZE_128M); > + else if (total_mem <= TOTAL_MEM_4G) > + size = clamp(iotlb_default_size * 4, SIZE_256M, > + SIZE_256M); > + else > + size = clamp(iotlb_default_size * 8, SIZE_512M, > + SIZE_512M); > + > + pr_info("SEV adjusted max SWIOTLB size = %luMB", > + size >> 20); > + } > + > + return size; > +} > + > void __init mem_encrypt_init(void) > { > if (!sme_me_mask) > diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h > index 046bb94bd4d6..01ae6d891327 100644 > --- a/include/linux/swiotlb.h > +++ b/include/linux/swiotlb.h > @@ -33,6 +33,7 @@ extern void swiotlb_init(int verbose); > int swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose); > extern unsigned long swiotlb_nr_tbl(void); > unsigned long swiotlb_size_or_default(void); > +extern void __init swiotlb_adjust(void); > extern int swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs); > extern void __init swiotlb_update_mem_attributes(void); > > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index c19379fabd20..66a9e627bb51 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -163,6 +163,33 @@ unsigned long swiotlb_size_or_default(void) > return size ? size : (IO_TLB_DEFAULT_SIZE); > } > > +unsigned long __init __weak arch_swiotlb_adjust(unsigned long size) > +{ > + return 0; > +} > + > +void __init swiotlb_adjust(void) > +{ > + unsigned long size; > + > + /* > + * If swiotlb parameter has not been specified, give a chance to > + * architectures such as those supporting memory encryption to > + * adjust/expand SWIOTLB size for their use. > + */ > + if (!io_tlb_nslabs) { > + size = arch_swiotlb_adjust(IO_TLB_DEFAULT_SIZE); > + if (size) { > + size = ALIGN(size, 1 << IO_TLB_SHIFT); > + io_tlb_nslabs = size >> IO_TLB_SHIFT; > + io_tlb_nslabs = ALIGN(io_tlb_nslabs, > IO_TLB_SEGSIZE); > + > + pr_info("architecture adjusted SWIOTLB slabs = > %lu\n", > + io_tlb_nslabs); > + } > + } > +} > + > void swiotlb_print_info(void) > { > unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT; > -- > 2.17.1 > > -- With Best Regards, Andy Shevchenko
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