| Message ID | 20240517132421.285667-1-dev.jain@arm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: kernel: Replace manual computation with macro | expand |
On Fri, May 17, 2024 at 06:54:21PM +0530, Dev Jain wrote: > diff --git a/arch/arm64/kernel/pi/map_range.c b/arch/arm64/kernel/pi/map_range.c > index 5410b2cac590..4b145be7f846 100644 > --- a/arch/arm64/kernel/pi/map_range.c > +++ b/arch/arm64/kernel/pi/map_range.c > @@ -31,14 +31,14 @@ void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot, > { > u64 cmask = (level == 3) ? CONT_PTE_SIZE - 1 : U64_MAX; > u64 protval = pgprot_val(prot) & ~PTE_TYPE_MASK; > - int lshift = (3 - level) * (PAGE_SHIFT - 3); > - u64 lmask = (PAGE_SIZE << lshift) - 1; > + int lshift = ARM64_HW_PGTABLE_LEVEL_SHIFT(level); > + u64 lmask = ((u64)1 << lshift) - 1; Nitpick: you can use 1UL instead of (u64)1. > > start &= PAGE_MASK; > pa &= PAGE_MASK; > > /* Advance tbl to the entry that covers start */ > - tbl += (start >> (lshift + PAGE_SHIFT)) % PTRS_PER_PTE; > + tbl += (start >> lshift) % PTRS_PER_PTE; I did the maths as well my own way and the change is correct: lshift + PAGE_SHIT == ARM64_HW_PGTABLE_LEVEL_SHIFT(level) It probably is easier to read this way, so: Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
On Fri, May 17, 2024 at 04:31:12PM +0100, Catalin Marinas wrote: > On Fri, May 17, 2024 at 06:54:21PM +0530, Dev Jain wrote: > > diff --git a/arch/arm64/kernel/pi/map_range.c b/arch/arm64/kernel/pi/map_range.c > > index 5410b2cac590..4b145be7f846 100644 > > --- a/arch/arm64/kernel/pi/map_range.c > > +++ b/arch/arm64/kernel/pi/map_range.c > > @@ -31,14 +31,14 @@ void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot, > > { > > u64 cmask = (level == 3) ? CONT_PTE_SIZE - 1 : U64_MAX; > > u64 protval = pgprot_val(prot) & ~PTE_TYPE_MASK; > > - int lshift = (3 - level) * (PAGE_SHIFT - 3); > > - u64 lmask = (PAGE_SIZE << lshift) - 1; > > + int lshift = ARM64_HW_PGTABLE_LEVEL_SHIFT(level); > > + u64 lmask = ((u64)1 << lshift) - 1; > > Nitpick: you can use 1UL instead of (u64)1. Or, rather than reinventing this again, how about: #include <linux/bits.h> u64 lmask = GENMASK_ULL(lshift - 1, 0); [...] Cheers ---Dave
On Thu, May 23, 2024 at 02:02:37PM +0100, Dave P Martin wrote: > On Fri, May 17, 2024 at 04:31:12PM +0100, Catalin Marinas wrote: > > On Fri, May 17, 2024 at 06:54:21PM +0530, Dev Jain wrote: > > > diff --git a/arch/arm64/kernel/pi/map_range.c b/arch/arm64/kernel/pi/map_range.c > > > index 5410b2cac590..4b145be7f846 100644 > > > --- a/arch/arm64/kernel/pi/map_range.c > > > +++ b/arch/arm64/kernel/pi/map_range.c > > > @@ -31,14 +31,14 @@ void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot, > > > { > > > u64 cmask = (level == 3) ? CONT_PTE_SIZE - 1 : U64_MAX; > > > u64 protval = pgprot_val(prot) & ~PTE_TYPE_MASK; > > > - int lshift = (3 - level) * (PAGE_SHIFT - 3); > > > - u64 lmask = (PAGE_SIZE << lshift) - 1; > > > + int lshift = ARM64_HW_PGTABLE_LEVEL_SHIFT(level); > > > + u64 lmask = ((u64)1 << lshift) - 1; > > > > Nitpick: you can use 1UL instead of (u64)1. > > Or, rather than reinventing this again, how about: > > #include <linux/bits.h> > > u64 lmask = GENMASK_ULL(lshift - 1, 0); Even better. Thanks Dave.
diff --git a/arch/arm64/kernel/pi/map_range.c b/arch/arm64/kernel/pi/map_range.c index 5410b2cac590..4b145be7f846 100644 --- a/arch/arm64/kernel/pi/map_range.c +++ b/arch/arm64/kernel/pi/map_range.c @@ -31,14 +31,14 @@ void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot, { u64 cmask = (level == 3) ? CONT_PTE_SIZE - 1 : U64_MAX; u64 protval = pgprot_val(prot) & ~PTE_TYPE_MASK; - int lshift = (3 - level) * (PAGE_SHIFT - 3); - u64 lmask = (PAGE_SIZE << lshift) - 1; + int lshift = ARM64_HW_PGTABLE_LEVEL_SHIFT(level); + u64 lmask = ((u64)1 << lshift) - 1; start &= PAGE_MASK; pa &= PAGE_MASK; /* Advance tbl to the entry that covers start */ - tbl += (start >> (lshift + PAGE_SHIFT)) % PTRS_PER_PTE; + tbl += (start >> lshift) % PTRS_PER_PTE; /* * Set the right block/page bits for this level unless we are
Use macro from pgtable-hwdef.h for better readability. I have boot tested this patch on all page table level configs, including LVA/LPA/LPA2 configurations, and forced 52 bit userspace VA. - Claim: There should be no functional change after applying this patch. Proof: lshift is being used only for computing lmask and tbl. It suffices to prove that lmask and tbl remain invariant. Let s = PAGE_SHIFT, l = level. new_lshift ---> (expand macro) = (s - 3) * (4 - l) + 3 = 4s - sl - 12 + 3l + 3 = 4s - sl + 3l - 9 = (3s - sl + 3l - 9) + s = s(3 - l) + 3(l - 3) + s = (3 - l) * (s - 3) + s = old_lshift + s Hence, new_lshift = old_lshift + PAGE_SHIFT. => tbl is invariant. Noting that old_lmask = (PAGE_SIZE << old_lshift) = ((1 << PAGE_SHIFT) << old_lshift) = (1 << (PAGE_SHIFT + old_lshift)) = (1 << new_lshift) = new_lmask, we are done. Q.E.D Signed-off-by: Dev Jain <dev.jain@arm.com> --- arch/arm64/kernel/pi/map_range.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)