| Message ID | 20240209115417.724638-4-ruansy.fnst@fujitsu.com |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RFC,1/5] cxl/core: correct length of DPA field masks | expand |
Shiyang Ruan wrote: > The length of Physical Address in General Media Event Record/DRAM Event > Record is 64-bit, so the field mask should be defined as such length. Can you include this user visible side-effect of this change. Looks like this could cause usages of CXL_DPA_FLAGS_MASK to return an incorrect result? > > Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> > --- > drivers/cxl/core/trace.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/cxl/core/trace.h b/drivers/cxl/core/trace.h > index 89445435303a..388a87d972c2 100644 > --- a/drivers/cxl/core/trace.h > +++ b/drivers/cxl/core/trace.h > @@ -253,11 +253,11 @@ TRACE_EVENT(cxl_generic_event, > * DRAM Event Record > * CXL rev 3.0 section 8.2.9.2.1.2; Table 8-44 > */ > -#define CXL_DPA_FLAGS_MASK 0x3F > +#define CXL_DPA_FLAGS_MASK 0x3FULL > #define CXL_DPA_MASK (~CXL_DPA_FLAGS_MASK) > > -#define CXL_DPA_VOLATILE BIT(0) > -#define CXL_DPA_NOT_REPAIRABLE BIT(1) > +#define CXL_DPA_VOLATILE BIT_ULL(0) > +#define CXL_DPA_NOT_REPAIRABLE BIT_ULL(1) > #define show_dpa_flags(flags) __print_flags(flags, "|", \ > { CXL_DPA_VOLATILE, "VOLATILE" }, \ > { CXL_DPA_NOT_REPAIRABLE, "NOT_REPAIRABLE" } \ > -- > 2.34.1 >
在 2024/2/10 14:34, Dan Williams 写道: > Shiyang Ruan wrote: >> The length of Physical Address in General Media Event Record/DRAM Event >> Record is 64-bit, so the field mask should be defined as such length. > > Can you include this user visible side-effect of this change. Looks like > this could cause usages of CXL_DPA_FLAGS_MASK to return an incorrect > result? Ok. Will change it to this: The length of Physical Address in General Media Event Record/DRAM Event Record is 64bit, per CXL Spec r3.0 - 8.2.9.2.1.1, Table 8-43. Currently CXL_DPA_FLAGS_MASK is defined as int (32bit), then CXL_DPA_MASK is a int too, it will be 0x00000000FFFFFFC0 while using "->dpa & CXL_DPA_MASK" to obtain real physical address (to drop flags in lower bits), in this case the higher 32bit of ->dpa will be lost. To avoid this, define CXL_DPA_FLAGS_MASK as 64bit: 0x3FULL. -- Thanks, Ruan. > >> >> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> >> --- >> drivers/cxl/core/trace.h | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/cxl/core/trace.h b/drivers/cxl/core/trace.h >> index 89445435303a..388a87d972c2 100644 >> --- a/drivers/cxl/core/trace.h >> +++ b/drivers/cxl/core/trace.h >> @@ -253,11 +253,11 @@ TRACE_EVENT(cxl_generic_event, >> * DRAM Event Record >> * CXL rev 3.0 section 8.2.9.2.1.2; Table 8-44 >> */ >> -#define CXL_DPA_FLAGS_MASK 0x3F >> +#define CXL_DPA_FLAGS_MASK 0x3FULL >> #define CXL_DPA_MASK (~CXL_DPA_FLAGS_MASK) >> >> -#define CXL_DPA_VOLATILE BIT(0) >> -#define CXL_DPA_NOT_REPAIRABLE BIT(1) >> +#define CXL_DPA_VOLATILE BIT_ULL(0) >> +#define CXL_DPA_NOT_REPAIRABLE BIT_ULL(1) >> #define show_dpa_flags(flags) __print_flags(flags, "|", \ >> { CXL_DPA_VOLATILE, "VOLATILE" }, \ >> { CXL_DPA_NOT_REPAIRABLE, "NOT_REPAIRABLE" } \ >> -- >> 2.34.1 >> > >
[ add Ira and Davidlohr ] Shiyang Ruan wrote: > > > 在 2024/2/10 14:34, Dan Williams 写道: > > Shiyang Ruan wrote: > >> The length of Physical Address in General Media Event Record/DRAM Event > >> Record is 64-bit, so the field mask should be defined as such length. > > > > Can you include this user visible side-effect of this change. Looks like > > this could cause usages of CXL_DPA_FLAGS_MASK to return an incorrect > > result? > > Ok. Will change it to this: > > The length of Physical Address in General Media Event Record/DRAM Event > Record is 64bit, per CXL Spec r3.0 - 8.2.9.2.1.1, Table 8-43. Currently > CXL_DPA_FLAGS_MASK is defined as int (32bit), then CXL_DPA_MASK is a int > too, it will be 0x00000000FFFFFFC0 while using "->dpa & CXL_DPA_MASK" to > obtain real physical address (to drop flags in lower bits), in this case > the higher 32bit of ->dpa will be lost. > > To avoid this, define CXL_DPA_FLAGS_MASK as 64bit: 0x3FULL. That part was clear, what is missing is the impact. For example, this bug only impacts the output of the dpa field in the cxl_general_media and cxl_dram tracepoints, but no other part of the CXL code. So in this case the impact of the bug is low, but in the worst case an wrong size mask could compromise the security / integrity of the system. So I would expect a changelog like this to make the importance of the fix clear and to notify the original stakeholders where the bug was introduced. --- The length of Physical Address in General Media Event Record/DRAM Event Record is 64-bit, so the field mask should be defined as such length. Otherwise, this causes cxl_general_media and cxl_dram tracepoints to mask off the upper-32-bits of DPA addresses. The cxl_poison event is unaffected. If userspace was doing its own DPA-to-HPA translation this could lead to incorrect page retirement decisions, but there is no known consumer (like rasdaemon) of this event today. Fixes: d54a531a430b ("cxl/mem: Trace General Media Event Record") Cc: <stable@vger.kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Ira Weiny <ira.weiny@intel.com> ---
diff --git a/drivers/cxl/core/trace.h b/drivers/cxl/core/trace.h index 89445435303a..388a87d972c2 100644 --- a/drivers/cxl/core/trace.h +++ b/drivers/cxl/core/trace.h @@ -253,11 +253,11 @@ TRACE_EVENT(cxl_generic_event, * DRAM Event Record * CXL rev 3.0 section 8.2.9.2.1.2; Table 8-44 */ -#define CXL_DPA_FLAGS_MASK 0x3F +#define CXL_DPA_FLAGS_MASK 0x3FULL #define CXL_DPA_MASK (~CXL_DPA_FLAGS_MASK) -#define CXL_DPA_VOLATILE BIT(0) -#define CXL_DPA_NOT_REPAIRABLE BIT(1) +#define CXL_DPA_VOLATILE BIT_ULL(0) +#define CXL_DPA_NOT_REPAIRABLE BIT_ULL(1) #define show_dpa_flags(flags) __print_flags(flags, "|", \ { CXL_DPA_VOLATILE, "VOLATILE" }, \ { CXL_DPA_NOT_REPAIRABLE, "NOT_REPAIRABLE" } \
The length of Physical Address in General Media Event Record/DRAM Event Record is 64-bit, so the field mask should be defined as such length. Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> --- drivers/cxl/core/trace.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)