The KSEGX() macro is defined to 32-bit sign extend the address argument and logically AND the result with 0xe0000000, with the final result usually compared against one of the CKSEG macros. However the literal 0xe0000000 is unsigned as the high bit is set, and is therefore zero-extended on 64-bit kernels, resulting in the sign extension bits of the argument being masked to zero. This results in the odd situation where: KSEGX(CKSEG0) != CKSEG0 (0xffffffff80000000 & 0x00000000e0000000) != 0xffffffff80000000) Fix this by 32-bit sign extending the 0xe0000000 literal using _ACAST32_. This will help some MIPS KVM code handling 32-bit guest addresses to work on 64-bit host kernels, but will also affect a couple of other users: - KSEGX in dec_kn01_be_backend() on a 64-bit DECstation kernel. Maciej has confirmed this is not a valid combination. - The SiByte DMA page ops KSEGX check in clear_page() and copy_page() on 64-bit SB1 kernels, which appears not to be designed with 64-bit segments in mind anyway. This would (perhaps unintentionally) have always fallen back to the CPU copy on 64-bit kernels anyway, so we make this explicit by making CONFIG_SIBYTE_DMA_PAGEOPS depend on 32BIT, so the change of KSEGX behaviour can't break anything. Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx> Cc: linux-mips@xxxxxxxxxxxxxx --- Changes in v2: - Clarify that the DEC code in question shouldn't get used with 64-bit kernels (thanks Maciej). - Make SIBYTE_DMA_PAGEOPS depend on 32BIT so the dependence is explicit and so we don't break anything. - Correct CKSEG -> CKSEG0 in patch description. --- arch/mips/Kconfig | 2 +- arch/mips/include/asm/addrspace.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index ac91939b9b75..86a9abd398f5 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -2195,7 +2195,7 @@ config RM7000_CPU_SCACHE config SIBYTE_DMA_PAGEOPS bool "Use DMA to clear/copy pages" - depends on CPU_SB1 + depends on CPU_SB1 && 32BIT help Instead of using the CPU to zero and copy pages, use a Data Mover channel. These DMA channels are otherwise unused by the standard diff --git a/arch/mips/include/asm/addrspace.h b/arch/mips/include/asm/addrspace.h index 3b0e51d5a613..c5b04e752e97 100644 --- a/arch/mips/include/asm/addrspace.h +++ b/arch/mips/include/asm/addrspace.h @@ -45,7 +45,7 @@ /* * Returns the kernel segment base of a given address */ -#define KSEGX(a) ((_ACAST32_ (a)) & 0xe0000000) +#define KSEGX(a) ((_ACAST32_(a)) & _ACAST32_(0xe0000000)) /* * Returns the physical address of a CKSEGx / XKPHYS address -- 2.4.10
