Re: [intel-sgx-kernel-dev] [PATCH RFC v3 07/12] intel_sgx: driver for Intel Software Guard Extensions

[Sean Christopherson <sean.j.christopherson@intel.com>]

On Mon, 2017-11-06 at 13:33 +0200, Jarkko Sakkinen wrote:
> On Mon, Nov 06, 2017 at 01:08:22PM +0200, Jarkko Sakkinen wrote:
> > 
> > On Thu, Nov 02, 2017 at 01:10:29PM -0700, Sean Christopherson wrote:
> > > 
> > > On Tue, 2017-10-10 at 17:32 +0300, Jarkko Sakkinen wrote:
> > > > 
> > > > +static int sgx_dev_init(struct device *parent, bool locked_msrs)
> > > > +{
> > > > +	struct sgx_context *sgx_dev;
> > > > +	unsigned int eax, ebx, ecx, edx;
> > > > +	unsigned long pa;
> > > > +	unsigned long size;
> > > > +	int ret;
> > > > +	int i;
> > > > +
> > > > +	pr_info("intel_sgx: " DRV_DESCRIPTION " v" DRV_VERSION "\n");
> > > > +
> > > > +	sgx_dev = sgxm_ctx_alloc(parent);
> > > > +
> > > > +	sgx_locked_msrs = locked_msrs;
> > > > +
> > > > +	cpuid_count(SGX_CPUID, SGX_CPUID_CAPABILITIES, &eax, &ebx,
> > > > &ecx,
> > > > &edx);
> > > > +	/* Only allow misc bits supported by the driver. */
> > > > +	sgx_misc_reserved = ~ebx | SGX_MISC_RESERVED_MASK;
> > > > +#ifdef CONFIG_X86_64
> > > > +	sgx_encl_size_max_64 = 1ULL << ((edx >> 8) & 0xFF);
> > > > +#endif
> > > > +	sgx_encl_size_max_32 = 1ULL << (edx & 0xFF);
> > > > +
> > > > +	if (boot_cpu_has(X86_FEATURE_OSXSAVE)) {
> > > > +		cpuid_count(SGX_CPUID, SGX_CPUID_ATTRIBUTES, &eax,
> > > > &ebx,
> > > > &ecx,
> > > > +			    &edx);
> > > > +		sgx_xfrm_mask = (((u64)edx) << 32) + (u64)ecx;
> > > > +
> > > > +		for (i = 2; i < 64; i++) {
> > > > +			cpuid_count(0x0D, i, &eax, &ebx, &ecx, &edx);
> > > > +			if ((1 << i) & sgx_xfrm_mask)
> > > > +				sgx_xsave_size_tbl[i] = eax + ebx;
> > > > +		}
> > > > +	}
> > > > +
> > > > +	for (i = 0; i < SGX_MAX_EPC_BANKS; i++) {
> > > > +		cpuid_count(SGX_CPUID, i + SGX_CPUID_EPC_BANKS, &eax,
> > > > &ebx,
> > > > +			    &ecx, &edx);
> > > > +		if (!(eax & 0xf))
> > > > +			break;
> > > > +
> > > > +		pa = ((u64)(ebx & 0xfffff) << 32) + (u64)(eax &
> > > > 0xfffff000);
> > > > +		size = ((u64)(edx & 0xfffff) << 32) + (u64)(ecx &
> > > > 0xfffff000);
> > > > +
> > > > +		dev_info(parent, "EPC bank 0x%lx-0x%lx\n", pa, pa +
> > > > size);
> > > > +
> > > > +		sgx_epc_banks[i].pa = pa;
> > > > +		sgx_epc_banks[i].size = size;
> > > > +	}
> > > > +
> > > > +	sgx_nr_epc_banks = i;
> > > > +
> > > > +	for (i = 0; i < sgx_nr_epc_banks; i++) {
> > > > +#ifdef CONFIG_X86_64
> > > > +		sgx_epc_banks[i].va = (unsigned long)
> > > > +			ioremap_cache(sgx_epc_banks[i].pa,
> > > > +				      sgx_epc_banks[i].size);
> > > > +		if (!sgx_epc_banks[i].va) {
> > > > +			sgx_nr_epc_banks = i;
> > > > +			ret = -ENOMEM;
> > > > +			goto out_iounmap;
> > > > +		}
> > > > +#endif
> > > > +		ret = sgx_add_epc_bank(sgx_epc_banks[i].pa,
> > > > +				       sgx_epc_banks[i].size, i);
> > > > +		if (ret) {
> > > > +			sgx_nr_epc_banks = i + 1;
> > > > +			goto out_iounmap;
> > > > +		}
> > > > +	}
> > > > +
> > > > +	ret = sgx_page_cache_init();
> > > > +	if (ret)
> > > > +		goto out_iounmap;
> > > > +
> > > > +	sgx_add_page_wq = alloc_workqueue("intel_sgx-add-page-wq",
> > > > +					  WQ_UNBOUND | WQ_FREEZABLE,
> > > > 1);
> > > > +	if (!sgx_add_page_wq) {
> > > > +		pr_err("intel_sgx: alloc_workqueue() failed\n");
> > > > +		ret = -ENOMEM;
> > > > +		goto out_iounmap;
> > > > +	}
> > > > +
> > > > +	ret = cdev_device_add(&sgx_dev->cdev, &sgx_dev->dev);
> > > > +	if (ret)
> > > > +		goto out_workqueue;
> > > > +
> > > > +	return 0;
> > > > +out_workqueue:
> > > > +	destroy_workqueue(sgx_add_page_wq);
> > > > +out_iounmap:
> > > sgx_page_cache_teardown() should be called here, else ksgxswapd and the
> > > list of
> > > EPC pages will leak.
> > > 
> > Thanks.
> > 
> > > 
> > > > 
> > > > +#ifdef CONFIG_X86_64
> > > > +	for (i = 0; i < sgx_nr_epc_banks; i++)
> > > > +		iounmap((void *)sgx_epc_banks[i].va);
> > > > +#endif
> > > > +	return ret;
> > > > +}
> > > ... 
> > > 
> > > > 
> > > > +int sgx_add_epc_bank(resource_size_t start, unsigned long size, int
> > > > bank)
> > > > +{
> > > > +	unsigned long i;
> > > > +	struct sgx_epc_page *new_epc_page, *entry;
> > > > +	struct list_head *parser, *temp;
> > > > +
> > > > +	for (i = 0; i < size; i += PAGE_SIZE) {
> > > > +		new_epc_page = kzalloc(sizeof(*new_epc_page),
> > > > GFP_KERNEL);
> > > > +		if (!new_epc_page)
> > > > +			goto err_freelist;
> > > > +		new_epc_page->pa = (start + i) | bank;
> > > > +
> > > > +		spin_lock(&sgx_free_list_lock);
> > > > +		list_add_tail(&new_epc_page->list, &sgx_free_list);
> > > > +		sgx_nr_total_epc_pages++;
> > > > +		sgx_nr_free_pages++;
> > > > +		spin_unlock(&sgx_free_list_lock);
> > > > +	}
> > > > +
> > > > +	return 0;
> > > > +err_freelist:
> > > > +	list_for_each_safe(parser, temp, &sgx_free_list) {
> > > > +		spin_lock(&sgx_free_list_lock);
> > > > +		entry = list_entry(parser, struct sgx_epc_page, list);
> > > > +		list_del(&entry->list);
> > > > +		spin_unlock(&sgx_free_list_lock);
> > > > +		kfree(entry);
> > > > +	}
> > > > +	return -ENOMEM;
> > > > +}
> > > Freeing the entire list on failure does not seem like the appropriate
> > > behavior
> > > for this helper func, e.g. the list should be purged by
> > > sgx_page_cache_teardown.
> > > Buffering the new pages into a local list and only splicing said list into
> > > the
> > > global list upon success is more inline with what I would expect from a
> > > helper
> > > func, and also only requires a single lock/unlock.
> > > 
> > > diff --git drivers/platform/x86/intel_sgx/sgx_page_cache.c
> > > drivers/platform/x86/intel_sgx/sgx_page_cache.c
> > > index f8883d24692a..38496e6296f1 100644
> > > --- drivers/platform/x86/intel_sgx/sgx_page_cache.c
> > > +++ drivers/platform/x86/intel_sgx/sgx_page_cache.c
> > > @@ -397,7 +397,8 @@ int sgx_add_epc_bank(resource_size_t start, unsigned
> > > long
> > > size, int bank)
> > >  {
> > >         unsigned long i;
> > >         struct sgx_epc_page *new_epc_page, *entry;
> > > -       struct list_head *parser, *temp;
> > > +       LIST_HEAD(epc_pages);
> > >  
> > >         for (i = 0; i < size; i += PAGE_SIZE) {
> > >                 new_epc_page = kzalloc(sizeof(*new_epc_page), GFP_KERNEL);
> > > @@ -405,22 +406,19 @@ int sgx_add_epc_bank(resource_size_t start, unsigned
> > > long
> > > size, int bank)
> > >                         goto err_freelist;
> > >                 new_epc_page->pa = (start + i) | bank;
> > >  
> > > -               spin_lock(&sgx_free_list_lock);
> > > -               list_add_tail(&new_epc_page->list, &sgx_free_list);
> > > -               sgx_nr_total_epc_pages++;
> > > -               sgx_nr_free_pages++;
> > > -               spin_unlock(&sgx_free_list_lock);
> > > +               list_add_tail(&new_epc_page->list, &epc_pages);
> > > +               nr_pages++;
> > >         }
> > >  
> > > +       spin_lock(&sgx_free_list_lock);
> > > +       list_splice_tail(&epc_pages, &sgx_free_list);
> > > +       sgx_nr_total_epc_pages += nr_pages;
> > > +       sgx_nr_free_pages += nr_pages;
> > > +       spin_unlock(&sgx_free_list_lock);
> > >         return 0;
> > >  err_freelist:
> > > -       list_for_each_safe(parser, temp, &sgx_free_list) {
> > > -               spin_lock(&sgx_free_list_lock);
> > > -               entry = list_entry(parser, struct sgx_epc_page, list);
> > > -               list_del(&entry->list);
> > > -               spin_unlock(&sgx_free_list_lock);
> > > +       list_for_each_entry(entry, &sgx_free_list, list)
> > >                 kfree(entry);
> > > -       }
> > >         return -ENOMEM;
> > >  }
> > This makes sense to me and I think it makes also sense to move bunch of
> > stuff from sgx_dev_init() to sgx_page_cache_init().
> > /Jarkko
> You can get away without nr_pages as you can get from i or am I
> misobserving something?

i is incremented by PAGE_SIZE.  I suppose you could do "+= i / PAGE_SIZE", but I
would opt for clarity in this case.