Messages in this thread | | | Date | Thu, 31 Mar 2022 11:59:37 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH v8 09/14] riscv: Fix accessing pfn bits in PTEs for non-32bit variants |
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On Thu, Mar 24, 2022 at 01:07:05AM +0100, Heiko Stuebner wrote: > On rv32 the PFN part of PTEs is defined to use bits [xlen-1:10] > while on rv64 it is defined to use bits [53:10], leaving [63:54] > as reserved. > > With upcoming optional extensions like svpbmt these previously > reserved bits will get used so simply right-shifting the PTE > to get the PFN won't be enough. > > So introduce a _PAGE_PFN_MASK constant to mask the correct bits > for both rv32 and rv64 before shifting. > > Signed-off-by: Heiko Stuebner <heiko@sntech.de> > --- > arch/riscv/include/asm/pgtable-32.h | 8 ++++++++ > arch/riscv/include/asm/pgtable-64.h | 14 +++++++++++--- > arch/riscv/include/asm/pgtable-bits.h | 6 ------ > arch/riscv/include/asm/pgtable.h | 6 +++--- > 4 files changed, 22 insertions(+), 12 deletions(-) > > diff --git a/arch/riscv/include/asm/pgtable-32.h b/arch/riscv/include/asm/pgtable-32.h > index 5b2e79e5bfa5..e266a4fe7f43 100644 > --- a/arch/riscv/include/asm/pgtable-32.h > +++ b/arch/riscv/include/asm/pgtable-32.h > @@ -7,6 +7,7 @@ > #define _ASM_RISCV_PGTABLE_32_H > > #include <asm-generic/pgtable-nopmd.h> > +#include <linux/bits.h> > #include <linux/const.h> > > /* Size of region mapped by a page global directory */ > @@ -16,4 +17,11 @@ > > #define MAX_POSSIBLE_PHYSMEM_BITS 34 > > +/* > + * rv32 PTE format: > + * | XLEN-1 10 | 9 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 > + * PFN reserved for SW D A G U X W R V > + */ > +#define _PAGE_PFN_MASK GENMASK(31, 10)
I have to say I really hate this obsfucating GENMASK macro, but it does have a few other uses in the riscv code.
> +/* > + * rv64 PTE format: > + * | 63 | 62 61 | 60 54 | 53 10 | 9 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 > + * N MT RSV PFN reserved for SW D A G U X W R V > + */ > > +#define _PAGE_PFN_MASK GENMASK(53, 10) > + > static inline int pud_present(pud_t pud) > { > return (pud_val(pud) & _PAGE_PRESENT); > @@ -91,12 +99,12 @@ static inline unsigned long _pud_pfn(pud_t pud) > > static inline pmd_t *pud_pgtable(pud_t pud) > { > - return (pmd_t *)pfn_to_virt(pud_val(pud) >> _PAGE_PFN_SHIFT); > + return (pmd_t *)pfn_to_virt((pud_val(pud) & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT);
Lots of overly long lins making this pretty unreadable.
But in general the (pfn & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT logic really should have a helper anyway.
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