| Message ID | 20210124062907.88229-6-tianjia.zhang@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Some optimizations related to sgx | expand |
On Sun, Jan 24, 2021 at 02:29:07PM +0800, Tianjia Zhang wrote: > In this scenario, there is no case where va_page is NULL, and > the error has been checked. The if condition statement here is > redundant, so remove the condition detection. > > Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com> > --- > arch/x86/kernel/cpu/sgx/ioctl.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c > index 1c6ecf9fbeff..b0b829f1b761 100644 > --- a/arch/x86/kernel/cpu/sgx/ioctl.c > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c > @@ -66,9 +66,11 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs) > va_page = sgx_encl_grow(encl); > if (IS_ERR(va_page)) > return PTR_ERR(va_page); > - else if (va_page) > - list_add(&va_page->list, &encl->va_pages); > - /* else the tail page of the VA page list had free slots. */ > + > + if (WARN_ONCE(!va_page, "non-empty VA page list before ECREATE")) > + return -EIO; So you just crashed machines that have panic-on-warn enabled. Don't do that for no reason, just handle the error and move on. thanks, greg k-h
On Sun, Jan 24, 2021, Greg KH wrote: > On Sun, Jan 24, 2021 at 02:29:07PM +0800, Tianjia Zhang wrote: > > In this scenario, there is no case where va_page is NULL, and > > the error has been checked. The if condition statement here is > > redundant, so remove the condition detection. > > > > Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com> > > --- > > arch/x86/kernel/cpu/sgx/ioctl.c | 8 +++++--- > > 1 file changed, 5 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c > > index 1c6ecf9fbeff..b0b829f1b761 100644 > > --- a/arch/x86/kernel/cpu/sgx/ioctl.c > > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c > > @@ -66,9 +66,11 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs) > > va_page = sgx_encl_grow(encl); > > if (IS_ERR(va_page)) > > return PTR_ERR(va_page); > > - else if (va_page) > > - list_add(&va_page->list, &encl->va_pages); > > - /* else the tail page of the VA page list had free slots. */ > > + > > + if (WARN_ONCE(!va_page, "non-empty VA page list before ECREATE")) > > + return -EIO; > > So you just crashed machines that have panic-on-warn enabled. Don't do > that for no reason, just handle the error and move on. The WARN will only fire if someone introduces a kernel bug. It's one part documentation, two parts helping detect future breakage. Even if the VA page management is significantly reworked, I'm having a hard time envisioning a scenario where adding VA pages before ECREATE would be anything but a kernel bug.
On Sun, Jan 24, 2021 at 02:29:07PM +0800, Tianjia Zhang wrote: > In this scenario, there is no case where va_page is NULL, and > the error has been checked. The if condition statement here is > redundant, so remove the condition detection. > > Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com> > --- > arch/x86/kernel/cpu/sgx/ioctl.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c > index 1c6ecf9fbeff..b0b829f1b761 100644 > --- a/arch/x86/kernel/cpu/sgx/ioctl.c > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c > @@ -66,9 +66,11 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs) > va_page = sgx_encl_grow(encl); > if (IS_ERR(va_page)) > return PTR_ERR(va_page); > - else if (va_page) > - list_add(&va_page->list, &encl->va_pages); > - /* else the tail page of the VA page list had free slots. */ This is fine. The check does not make sense. > + > + if (WARN_ONCE(!va_page, "non-empty VA page list before ECREATE")) > + return -EIO; No need for this WARN_ONCE(). > + > + list_add(&va_page->list, &encl->va_pages); This is fine. > > /* The extra page goes to SECS. */ > encl_size = secs->size + PAGE_SIZE; > -- > 2.19.1.3.ge56e4f7 > > /Jarkko
On 1/30/21 10:33 PM, Jarkko Sakkinen wrote: > On Sun, Jan 24, 2021 at 02:29:07PM +0800, Tianjia Zhang wrote: >> In this scenario, there is no case where va_page is NULL, and >> the error has been checked. The if condition statement here is >> redundant, so remove the condition detection. >> >> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com> >> --- >> arch/x86/kernel/cpu/sgx/ioctl.c | 8 +++++--- >> 1 file changed, 5 insertions(+), 3 deletions(-) >> >> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c >> index 1c6ecf9fbeff..b0b829f1b761 100644 >> --- a/arch/x86/kernel/cpu/sgx/ioctl.c >> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c >> @@ -66,9 +66,11 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs) >> va_page = sgx_encl_grow(encl); >> if (IS_ERR(va_page)) >> return PTR_ERR(va_page); >> - else if (va_page) >> - list_add(&va_page->list, &encl->va_pages); >> - /* else the tail page of the VA page list had free slots. */ > > This is fine. The check does not make sense. > >> + >> + if (WARN_ONCE(!va_page, "non-empty VA page list before ECREATE")) >> + return -EIO; > > No need for this WARN_ONCE(). > >> + >> + list_add(&va_page->list, &encl->va_pages); > > This is fine. > >> >> /* The extra page goes to SECS. */ >> encl_size = secs->size + PAGE_SIZE; >> -- >> 2.19.1.3.ge56e4f7 >> >> > > /Jarkko > Will be improved in the next version. Thanks, Tianjia
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c index 1c6ecf9fbeff..b0b829f1b761 100644 --- a/arch/x86/kernel/cpu/sgx/ioctl.c +++ b/arch/x86/kernel/cpu/sgx/ioctl.c @@ -66,9 +66,11 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs) va_page = sgx_encl_grow(encl); if (IS_ERR(va_page)) return PTR_ERR(va_page); - else if (va_page) - list_add(&va_page->list, &encl->va_pages); - /* else the tail page of the VA page list had free slots. */ + + if (WARN_ONCE(!va_page, "non-empty VA page list before ECREATE")) + return -EIO; + + list_add(&va_page->list, &encl->va_pages); /* The extra page goes to SECS. */ encl_size = secs->size + PAGE_SIZE;
In this scenario, there is no case where va_page is NULL, and the error has been checked. The if condition statement here is redundant, so remove the condition detection. Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com> --- arch/x86/kernel/cpu/sgx/ioctl.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)