[v9,2/7] x86/sgx: Add infrastructure to identify SGX EPC pages

Commit Message

Tony Luck Oct. 11, 2021, 6:59 p.m. UTC

X86 machine check architecture reports a physical address when there
is a memory error. Handling that error requires a method to determine
whether the physical address reported is in any of the areas reserved
for EPC pages by BIOS.

SGX EPC pages do not have Linux "struct page" associated with them.

Keep track of the mapping from ranges of EPC pages to the sections
that contain them using an xarray.

Create a function arch_is_platform_page() that simply reports whether an
address is an EPC page for use elsewhere in the kernel. The ACPI error
injection code needs this function and is typically built as a module,
so export it.

Note that arch_is_platform_page() will be slower than other similar
"what type is this page" functions that can simply check bits in the
"struct page".  If there is some future performance critical user of
this function it may need to be implemented in a more efficient way.

Note also that the current implementation of xarray allocates a few
hundred kilobytes for this usage on a system with 4GB of SGX EPC memory
configured. This isn't ideal, but worth it for the code simplicity.

Reviewed-by: Jarkko Sakkinen <[e-mail]>
Tested-by: Reinette Chatre <[e-mail]>
Signed-off-by: Tony Luck <[e-mail]>
---
 arch/x86/kernel/cpu/sgx/main.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Comments

kernel test robot Oct. 22, 2021, 10:43 a.m. UTC | #1

Hi Tony,

I love your patch! Yet something to improve:

[auto build test ERROR on rafael-pm/linux-next]
[also build test ERROR on hnaz-mm/master tip/x86/sgx v5.15-rc6 next-20211021]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Tony-Luck/x86-sgx-Add-new-sgx_epc_page-flag-bit-to-mark-in-use-pages/20211012-035926
base:   https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next
config: x86_64-randconfig-a011-20211011 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/9c7bd2907252bfbf4948be9855e3535319e1e9e4
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Tony-Luck/x86-sgx-Add-new-sgx_epc_page-flag-bit-to-mark-in-use-pages/20211012-035926
        git checkout 9c7bd2907252bfbf4948be9855e3535319e1e9e4
        # save the attached .config to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[e-mail]>

All errors (new ones prefixed by >>):

   ld: arch/x86/kernel/cpu/sgx/main.o: in function `sgx_setup_epc_section':
>> arch/x86/kernel/cpu/sgx/main.c:654: undefined reference to `xa_store_range'


vim +654 arch/x86/kernel/cpu/sgx/main.c

   635	
   636	static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
   637						 unsigned long index,
   638						 struct sgx_epc_section *section)
   639	{
   640		unsigned long nr_pages = size >> PAGE_SHIFT;
   641		unsigned long i;
   642	
   643		section->virt_addr = memremap(phys_addr, size, MEMREMAP_WB);
   644		if (!section->virt_addr)
   645			return false;
   646	
   647		section->pages = vmalloc(nr_pages * sizeof(struct sgx_epc_page));
   648		if (!section->pages) {
   649			memunmap(section->virt_addr);
   650			return false;
   651		}
   652	
   653		section->phys_addr = phys_addr;
 > 654		xa_store_range(&sgx_epc_address_space, section->phys_addr,
   655			       phys_addr + size - 1, section, GFP_KERNEL);
   656	
   657		for (i = 0; i < nr_pages; i++) {
   658			section->pages[i].section = index;
   659			section->pages[i].flags = SGX_EPC_PAGE_IN_USE;
   660			section->pages[i].owner = NULL;
   661			list_add_tail(&section->pages[i].list, &sgx_dirty_page_list);
   662		}
   663	
   664		return true;
   665	}
   666	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[e-mail]

Patch

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index d18988a46c13..09fa42690ff2 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -20,6 +20,7 @@  struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
 static int sgx_nr_epc_sections;
 static struct task_struct *ksgxd_tsk;
 static DECLARE_WAIT_QUEUE_HEAD(ksgxd_waitq);
+static DEFINE_XARRAY(sgx_epc_address_space);
 
 /*
  * These variables are part of the state of the reclaimer, and must be accessed
@@ -650,6 +651,8 @@  static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
 	}
 
 	section->phys_addr = phys_addr;
+	xa_store_range(&sgx_epc_address_space, section->phys_addr,
+		       phys_addr + size - 1, section, GFP_KERNEL);
 
 	for (i = 0; i < nr_pages; i++) {
 		section->pages[i].section = index;
@@ -661,6 +664,12 @@  static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
 	return true;
 }
 
+bool arch_is_platform_page(u64 paddr)
+{
+	return !!xa_load(&sgx_epc_address_space, paddr);
+}
+EXPORT_SYMBOL_GPL(arch_is_platform_page);
+
 /**
  * A section metric is concatenated in a way that @low bits 12-31 define the
  * bits 12-31 of the metric and @high bits 0-19 define the bits 32-51 of the