Hi Andrey,
On Wed, Dec 2, 2020 at 8:11 AM Andrey Zhizhikin andrey.zhizhikin@leica-geosystems.com wrote:
ARMv7 Architecture Reference Manual [1] section A3.5.5 details Normal memory type, together with cacheability attributes that could be applied to memory regions defined as "Normal memory".
Section B2.1.2 of the Architecture Reference Manual [1] also provides details regarding the Memory attributes that could be assigned to particular memory regions, which includes the descrption of cacheability attributes and cache allocation hints.
Memory type and cacheability attributes forms 2 separate definitions, where cacheability attributes defines a mechanism of coherency control rather than the type of memory itself.
In other words: Normal memory type can be configured with several combination of cacheability attributes, namely:
- Write-Through (WT)
- Write-Back (WB) followed by cache allocation hint:
- Write-Allocate
- No Write-Allocate (also known as Read-Allocate)
Those types are mapped in the kernel to corresponding macros:
- Write-Through: L_PTE_MT_WRITETHROUGH
- Write-Back Write-Allocate: L_PTE_MT_WRITEALLOC
- Write-Back Read-Allocate: L_PTE_MT_WRITEBACK
Current implementation of the op-tee driver takes in account only 2 last memory region types, while performing a check if the memory block is allocated as "Normal memory", leaving Write-Through allocations to be not considered.
Extend verification mechanism to include also Normal memory regios, which are designated with Write-Through cacheability attributes.
Are you trying to fix a real error with this or are you just trying to cover all cases? I suspect the latter since you'd likely have coherency problems with OP-TEE in Secure world if you used Write-Through instead. Correct me if I'm wrong, but "Write-Back Write-Allocate" and "Write-Back Read-Allocate" are both compatible with each other as the "Allocate" part is just a hint.
Cheers, Jens
Link: [1]: https://developer.arm.com/documentation/ddi0406/cd Fixes: 853735e40424 ("optee: add writeback to valid memory type") Cc: stable@vger.kernel.org Signed-off-by: Andrey Zhizhikin andrey.zhizhikin@leica-geosystems.com
drivers/tee/optee/call.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c index c981757ba0d4..8da27d02a2d6 100644 --- a/drivers/tee/optee/call.c +++ b/drivers/tee/optee/call.c @@ -535,7 +535,8 @@ static bool is_normal_memory(pgprot_t p) { #if defined(CONFIG_ARM) return (((pgprot_val(p) & L_PTE_MT_MASK) == L_PTE_MT_WRITEALLOC) ||
((pgprot_val(p) & L_PTE_MT_MASK) == L_PTE_MT_WRITEBACK));
((pgprot_val(p) & L_PTE_MT_MASK) == L_PTE_MT_WRITEBACK) ||((pgprot_val(p) & L_PTE_MT_MASK) == L_PTE_MT_WRITETHROUGH));#elif defined(CONFIG_ARM64) return (pgprot_val(p) & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL);
#else
2.17.1