On Fri, Mar 05, 2021 at 04:20:58PM -0800, 'Ira Weiny' 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.
Friendly ping, maybe I missed a response? Ira > > 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(PAGE_SIZE, ...) > to get a page aligned 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. > > Cc: Sean Christopherson <sea...@google.com> > Cc: Jethro Beekman <jet...@fortanix.com> > Reviewed-by: Jarkko Sakkinen <jar...@kernel.org> > Acked-by: Dave Hansen <dave.han...@intel.com> > Signed-off-by: Ira Weiny <ira.we...@intel.com> > > --- > Changes from v4[4]: > Add Ack and Reviews > Send to the correct maintainers > > Changes from v3[3]: > Remove BUILD_BUG_ONs > > Changes from v2[2]: > 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/ > [3] > https://lore.kernel.org/lkml/20210205050850.gc5...@iweiny-desk2.sc.intel.com/#t > [4] https://lore.kernel.org/lkml/ycby02ieklvyj...@kernel.org/ > > --- > arch/x86/kernel/cpu/sgx/ioctl.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c > index 90a5caf76939..38e540de5e2a 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 +614,14 @@ 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); > token = (void *)((unsigned long)sigstruct + PAGE_SIZE / 2); > memset(token, 0, SGX_LAUNCH_TOKEN_SIZE); > > @@ -645,8 +647,7 @@ 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 >
