Messages in this thread Patch in this message | | | Date | Wed, 18 Nov 2020 23:39:16 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v5] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests. |
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On Wed, Nov 18, 2020 at 08:12:43PM +0000, Ashish Kalra wrote: > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index 3511736fbc74..0f42911cea57 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -1166,6 +1166,10 @@ void __init setup_arch(char **cmdline_p) > if (boot_cpu_has(X86_FEATURE_GBPAGES)) > hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT); > > +#ifdef CONFIG_X86_64 > + swiotlb_adjust(); > +#endif
Add an empty stub in include/linux/swiotlb.h for the !CONFIG_SWIOTLB case and get rid of the ifdeffery please.
> +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 <= SZ_1G) > + size = max(iotlb_default_size, (unsigned long) SZ_128M); > + else if (total_mem <= SZ_4G) > + size = max(iotlb_default_size, (unsigned long) SZ_256M); > + else > + size = max(iotlb_default_size, (unsigned long) SZ_512M); > + > + pr_info("SEV adjusted max SWIOTLB size = %luMB",
Please make that message more user-friendly.
...
> +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",
That one too: what does "architecture adjusted SWIOTLB slabs" even mean?! Put yourself in your code user's shoes and see if that message makes sense to her/him.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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