Messages in this thread | | | Date | Mon, 2 Aug 2021 11:48:44 +0300 | From | Jarkko Sakkinen <> | Subject | Re: [PATCH v3 2/7] x86/sgx: Add infrastructure to identify SGX EPC pages |
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On Fri, Jul 30, 2021 at 04:46:07PM +0000, Sean Christopherson wrote: > On Fri, Jul 30, 2021, Jarkko Sakkinen wrote: > > On Wed, Jul 28, 2021 at 03:19:46PM -0700, Dave Hansen wrote: > > > On 7/28/21 1:46 PM, Tony Luck wrote: > > > > Export a function sgx_is_epc_page() that simply reports whether an > > > > address is an EPC page for use elsewhere in the kernel. > > > > > > It would be really nice to mention why this needs to be exported to > > > modules. I assume it's the error injection driver or something that can > > > be built as a module, but this export was a surprise when I saw it. > > > > > > It's probably also worth noting that this is a sloooooooow > > > implementation compared to the core VM code that does something > > > analogous: pfn_to_page(). It's fine for error handling, but we should > > > probably have a comment to this effect so that more liberal use doesn't > > > creep in anywhere. > > > > You could also create an xarray to track physical EPC address ranges, > > and make the query fast. > > Eh, it's not _that_ slow due to the constraints on the number of EPC sections. > The hard limit is currently '8', and practically speaking there will be one > section per socket. Turning a linear search into a binary search in this case > isn't going to buy much.
Also, consumes more memory.
Just pointing out that it is possible to improve without much fuzz, if ever required, for instance by using DEFINE_XARRAY() to be define file-scope xarray.
> Out of curiosity, on multi-socket systems, are EPC sections clustered in a single > address range, or are they interleaved with regular RAM? If they're clustered, > you could track the min/max across all sections to optimize the common case that > an address isn't in any EPC section.
Given that physical address ranges of different NUMA nodes are disjoint, and each has EPC section is reserved from one such section, I would presume that they are interleaved.
> static struct sgx_epc_page *sgx_paddr_to_page(u64 paddr) > { > struct sgx_epc_section *section; > int i; > > if (paddr < min_epc_pa || paddr > max_epc_pa) > return NULL; > > for (i = 0; i < ARRAY_SIZE(sgx_epc_sections); i++) { > section = &sgx_epc_sections[i]; > > if (paddr < section->phys_addr || paddr > section->end_phys_addr) > continue; > > return §ion->pages[PFN_DOWN(paddr - section->phys_addr)]; > } > > return NULL; > }
/Jarkko
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