From: Ira Weiny <[email protected]>
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(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 <[email protected]>
Cc: Jethro Beekman <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
Acked-by: Dave Hansen <[email protected]>
Signed-off-by: Ira Weiny <[email protected]>
---
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/[email protected]/
[2] https://lore.kernel.org/lkml/[email protected]/
[3] https://lore.kernel.org/lkml/[email protected]/#t
[4] https://lore.kernel.org/lkml/[email protected]/
---
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
On Fri, Mar 05, 2021 at 04:20:58PM -0800, 'Ira Weiny' wrote:
> From: Ira Weiny <[email protected]>
>
> 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 <[email protected]>
> Cc: Jethro Beekman <[email protected]>
> Reviewed-by: Jarkko Sakkinen <[email protected]>
> Acked-by: Dave Hansen <[email protected]>
> Signed-off-by: Ira Weiny <[email protected]>
>
> ---
> 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/[email protected]/
> [2] https://lore.kernel.org/lkml/[email protected]/
> [3] https://lore.kernel.org/lkml/[email protected]/#t
> [4] https://lore.kernel.org/lkml/[email protected]/
>
> ---
> 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
>
On Fri, Mar 05, 2021 at 04:20:58PM -0800, [email protected] wrote:
> Subject: Re: [PATCH v5] x86: Remove unnecessary kmap() from sgx_ioc_enclave_init()
The tip tree preferred format for patch subject prefixes is
'subsys/component:', e.g. 'x86/apic:', 'x86/mm/fault:', 'sched/fair:',
'genirq/core:'. Please do not use file names or complete file paths as
prefix. 'git log path/to/file' should give you a reasonable hint in most
cases.
> From: Ira Weiny <[email protected]>
>
> kmap is inefficient and we are trying to reduce the usage in the kernel.
Please use passive voice in your commit message: no "we" or "I", etc,
and describe your changes in imperative mood.
Also, pls read section "2) Describe your changes" in
Documentation/process/submitting-patches.rst for more details.
Bottom line is: personal pronouns are ambiguous in text, especially with
so many parties/companies/etc developing the kernel so let's avoid them
please.
> @@ -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
Please integrate scripts/checkpatch.pl into your patch creation
workflow. Some of the warnings/errors *actually* make sense.
WARNING: 'boundry' may be misspelled - perhaps 'boundary'?
#90: FILE: arch/x86/kernel/cpu/sgx/ioctl.c:618:
+ * sigstruct must be on a page boundry and token on a 512 byte boundry
^^^^^^^
WARNING: 'boundry' may be misspelled - perhaps 'boundary'?
#90: FILE: arch/x86/kernel/cpu/sgx/ioctl.c:618:
+ * sigstruct must be on a page boundry and token on a 512 byte boundry
^^^^^^^
Also, do you see how other comments in this file are proper sentences?
Please formulate yours this way too.
The change itself looks ok.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On Wed, Mar 24, 2021 at 10:47:20AM +0100, Borislav Petkov wrote:
> On Fri, Mar 05, 2021 at 04:20:58PM -0800, [email protected] wrote:
>
> > Subject: Re: [PATCH v5] x86: Remove unnecessary kmap() from sgx_ioc_enclave_init()
>
> The tip tree preferred format for patch subject prefixes is
> 'subsys/component:', e.g. 'x86/apic:', 'x86/mm/fault:', 'sched/fair:',
> 'genirq/core:'. Please do not use file names or complete file paths as
> prefix. 'git log path/to/file' should give you a reasonable hint in most
> cases.
Fixed.
>
> > From: Ira Weiny <[email protected]>
> >
> > kmap is inefficient and we are trying to reduce the usage in the kernel.
>
> Please use passive voice in your commit message: no "we" or "I", etc,
> and describe your changes in imperative mood.
>
> Also, pls read section "2) Describe your changes" in
> Documentation/process/submitting-patches.rst for more details.
>
> Bottom line is: personal pronouns are ambiguous in text, especially with
> so many parties/companies/etc developing the kernel so let's avoid them
> please.
Fixed.
>
> > @@ -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
>
> Please integrate scripts/checkpatch.pl into your patch creation
> workflow. Some of the warnings/errors *actually* make sense.
>
> WARNING: 'boundry' may be misspelled - perhaps 'boundary'?
> #90: FILE: arch/x86/kernel/cpu/sgx/ioctl.c:618:
> + * sigstruct must be on a page boundry and token on a 512 byte boundry
> ^^^^^^^
>
> WARNING: 'boundry' may be misspelled - perhaps 'boundary'?
> #90: FILE: arch/x86/kernel/cpu/sgx/ioctl.c:618:
> + * sigstruct must be on a page boundry and token on a 512 byte boundry
> ^^^^^^^
>
> Also, do you see how other comments in this file are proper sentences?
> Please formulate yours this way too.
Thanks fixed.
>
> The change itself looks ok.
Thanks, new version 5 sent.
Ira
>
> Thx.
>
> --
> Regards/Gruss,
> Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette