On Wed, Feb 03, 2021 at 12:45:33AM +0200, Jarkko Sakkinen wrote: > On Tue, Feb 02, 2021 at 11:47:19AM -0800, ira.we...@intel.com wrote: > > From: Ira Weiny <ira.we...@intel.com> > > > > kmap is inefficient and we are trying to reduce the usage in the kernel. > > There is no readily apparent reason why initp_page needs to be allocated > > and kmap'ed() but sigstruct needs to be page aligned and token > > 512 byte aligned. > > > > kmalloc() can give us this alignment but we need to allocate PAGE_SIZE > > bytes to do so. Rather than change this kmap() to kmap_local_page() use > > kmalloc() instead. > > > > Remove the alloc_page()/kmap() and replace with kmalloc() to get a > > kernel address to use. > > > > In addition add a comment to document the alignment requirements so that > > others like myself don't attempt to 'fix' this again. Finally, add 2 > > BUILD_BUG_ON's to ensure future changes to sigstruct and token do not go > > unnoticed and cause a bug. > > > > Cc: Dave Hansen <dave.han...@intel.com> > > Cc: Sean Christopherson <sea...@google.com> > > Cc: Jethro Beekman <jet...@fortanix.com> > > Signed-off-by: Ira Weiny <ira.we...@intel.com> > > > > --- > > Changes from v2[1]: > > When allocating a power of 2 size kmalloc() now guarantees the > > alignment of the respective size. So go back to using kmalloc() but > > with a PAGE_SIZE allocation to get the alignment. This also follows > > the pattern in sgx_ioc_enclave_create() > > > > Changes from v1[1]: > > Use page_address() instead of kcmalloc() to ensure sigstruct is > > page aligned > > Use BUILD_BUG_ON to ensure token and sigstruct don't collide. > > > > [1] > > https://lore.kernel.org/lkml/20210129001459.1538805-1-ira.we...@intel.com/ > > [2] > > https://lore.kernel.org/lkml/20210202013725.3514671-1-ira.we...@intel.com/ > > --- > > arch/x86/kernel/cpu/sgx/ioctl.c | 15 +++++++++------ > > 1 file changed, 9 insertions(+), 6 deletions(-) > > > > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c > > b/arch/x86/kernel/cpu/sgx/ioctl.c > > index 90a5caf76939..e0c3301ccd67 100644 > > --- a/arch/x86/kernel/cpu/sgx/ioctl.c > > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c > > @@ -604,7 +604,6 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, > > void __user *arg) > > { > > struct sgx_sigstruct *sigstruct; > > struct sgx_enclave_init init_arg; > > - struct page *initp_page; > > void *token; > > int ret; > > > > @@ -615,11 +614,16 @@ static long sgx_ioc_enclave_init(struct sgx_encl > > *encl, void __user *arg) > > if (copy_from_user(&init_arg, arg, sizeof(init_arg))) > > return -EFAULT; > > > > - initp_page = alloc_page(GFP_KERNEL); > > - if (!initp_page) > > + /* > > + * sigstruct must be on a page boundry and token on a 512 byte boundry > > + * kmalloc() gives us this alignment when allocating PAGE_SIZE bytes > > + */ > > + sigstruct = kmalloc(PAGE_SIZE, GFP_KERNEL); > > + if (!sigstruct) > > return -ENOMEM; > > > > - sigstruct = kmap(initp_page); > > + BUILD_BUG_ON(sizeof(*sigstruct) > (PAGE_SIZE/2)); > > + BUILD_BUG_ON(SGX_LAUNCH_TOKEN_SIZE > (PAGE_SIZE/2)); > > Please remove these.
I don't see why these would be a bad thing as they don't have any run time implications. But I've removed them for v4 because getting rid of the kmap() is more important for me right now. Ira > > > token = (void *)((unsigned long)sigstruct + PAGE_SIZE / 2); > > memset(token, 0, SGX_LAUNCH_TOKEN_SIZE); > > > > @@ -645,8 +649,7 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, > > void __user *arg) > > ret = sgx_encl_init(encl, sigstruct, token); > > > > out: > > - kunmap(initp_page); > > - __free_page(initp_page); > > + kfree(sigstruct); > > return ret; > > } > > > > -- > > 2.28.0.rc0.12.gb6a658bd00c9 > > > > > > /Jarkko
