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 ZfhwgwCb 1+/yLOtiwSg69BGNk8vvX4VRXibPSxl0sqdANUqYnkY2mazU88y8cXom3brDko3cpbQ+uQY6CkVC7kbSKvPX3/81neO4PIjmL3ZI0v+fS/ywMxzPh2e3lk3YfDQap4Cc66QxW29kHPOV5cPwlnnV+0ioeo56mO1yUNXXQZ8gvcjryitgH1YNahHarQoCQ/kSwETomEuQtDJJ1SeMODAdR936dTxGXURiyuE0lKgLVCQbQ4OAYJqeqs/gKYE32YTcsQXDUsTp/uF4KlI6iZiogYBPL2oLDwdz+IAsX0rGlKGwELptOjXICxCnRelZ1xOt6neLN5RMmsPi+GtcBLTgRmjGffcMWlsbBoqdLaPHAce8DaL5dMqK0vbYzVBM9Ab4KMW5TkcgwIuzOjteukgxhgfn7ovyfl3JraETpNVq38LWcNH8hTusm0sgVsnf6Mg4ujwJ3/w842RqjZ9AB4/djvs2ufMNs5kyNsZmTI4NsPunIc9QLbdKQfOAwWQwmkotfXUt+sWl2/A2upE67kBoRyRBD3JLYXFpyFH6DH0AFFG/4vc350zHR208GE6v+2e74/Qsy7xNI3bVvPyqQsXRTeACAMrsAxa5uRDIJvgSzvUJOyG+xuWrs1eYpYbSy+t9TAPGi3yvdcMdbL+beICQPkrKCYfqr5aiAnHxfjAoA7cv4dGSjkOjKmzf9EBdmjHuurN/2 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/29/25 4:52 AM, Ryan Roberts wrote: > When splitting kernel leaf mappings, either via > split_kernel_leaf_mapping_locked() or linear_map_split_to_ptes(), > previously a leaf mapping was always split to the next size down. e.g. > pud -> contpmd -> pmd -> contpte -> pte. But for > linear_map_split_to_ptes() we can avoid the contpmd and contpte states > because we know we want to split all the way down to ptes. > > This avoids visiting all the ptes in a table if it was created by > splitting a pmd, which is noticible on systems with a lot of memory. Similar to patch #4, this patch should be squashed into patch #5 IMHO. Thanks, Yang > > Signed-off-by: Ryan Roberts > --- > arch/arm64/mm/mmu.c | 26 ++++++++++++++++++-------- > 1 file changed, 18 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 6bd0b065bd97..8e45cd08bf3a 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -550,7 +550,7 @@ static void split_contpte(pte_t *ptep) > __set_pte(ptep, pte_mknoncont(__ptep_get(ptep))); > } > > -static int split_pmd(pmd_t *pmdp, pmd_t pmd, gfp_t gfp) > +static int split_pmd(pmd_t *pmdp, pmd_t pmd, gfp_t gfp, bool to_cont) > { > pmdval_t tableprot = PMD_TYPE_TABLE | PMD_TABLE_UXN | PMD_TABLE_AF; > unsigned long pfn = pmd_pfn(pmd); > @@ -568,7 +568,9 @@ static int split_pmd(pmd_t *pmdp, pmd_t pmd, gfp_t gfp) > tableprot |= PMD_TABLE_PXN; > > prot = __pgprot((pgprot_val(prot) & ~PTE_TYPE_MASK) | PTE_TYPE_PAGE); > - prot = __pgprot(pgprot_val(prot) | PTE_CONT); > + prot = __pgprot(pgprot_val(prot) & ~PTE_CONT); > + if (to_cont) > + prot = __pgprot(pgprot_val(prot) | PTE_CONT); > > for (i = 0; i < PTRS_PER_PTE; i++, ptep++, pfn++) > __set_pte(ptep, pfn_pte(pfn, prot)); > @@ -592,7 +594,7 @@ static void split_contpmd(pmd_t *pmdp) > set_pmd(pmdp, pmd_mknoncont(pmdp_get(pmdp))); > } > > -static int split_pud(pud_t *pudp, pud_t pud, gfp_t gfp) > +static int split_pud(pud_t *pudp, pud_t pud, gfp_t gfp, bool to_cont) > { > pudval_t tableprot = PUD_TYPE_TABLE | PUD_TABLE_UXN | PUD_TABLE_AF; > unsigned int step = PMD_SIZE >> PAGE_SHIFT; > @@ -611,7 +613,9 @@ static int split_pud(pud_t *pudp, pud_t pud, gfp_t gfp) > tableprot |= PUD_TABLE_PXN; > > prot = __pgprot((pgprot_val(prot) & ~PMD_TYPE_MASK) | PMD_TYPE_SECT); > - prot = __pgprot(pgprot_val(prot) | PTE_CONT); > + prot = __pgprot(pgprot_val(prot) & ~PTE_CONT); > + if (to_cont) > + prot = __pgprot(pgprot_val(prot) | PTE_CONT); > > for (i = 0; i < PTRS_PER_PMD; i++, pmdp++, pfn += step) > set_pmd(pmdp, pfn_pmd(pfn, prot)); > @@ -669,7 +673,7 @@ static int split_kernel_leaf_mapping_locked(unsigned long addr) > if (!pud_present(pud)) > goto out; > if (pud_leaf(pud)) { > - ret = split_pud(pudp, pud, GFP_PGTABLE_KERNEL); > + ret = split_pud(pudp, pud, GFP_PGTABLE_KERNEL, true); > if (ret) > goto out; > } > @@ -694,7 +698,7 @@ static int split_kernel_leaf_mapping_locked(unsigned long addr) > */ > if (ALIGN_DOWN(addr, PMD_SIZE) == addr) > goto out; > - ret = split_pmd(pmdp, pmd, GFP_PGTABLE_KERNEL); > + ret = split_pmd(pmdp, pmd, GFP_PGTABLE_KERNEL, true); > if (ret) > goto out; > } > @@ -771,7 +775,7 @@ static int __init split_to_ptes_pud_entry(pud_t *pudp, unsigned long addr, > int ret = 0; > > if (pud_leaf(pud)) > - ret = split_pud(pudp, pud, GFP_ATOMIC); > + ret = split_pud(pudp, pud, GFP_ATOMIC, false); > > return ret; > } > @@ -786,7 +790,13 @@ static int __init split_to_ptes_pmd_entry(pmd_t *pmdp, unsigned long addr, > if (pmd_leaf(pmd)) { > if (pmd_cont(pmd)) > split_contpmd(pmdp); > - ret = split_pmd(pmdp, pmd, GFP_ATOMIC); > + ret = split_pmd(pmdp, pmd, GFP_ATOMIC, false); > + > + /* > + * We have split the pmd directly to ptes so there is no need to > + * visit each pte to check if they are contpte. > + */ > + walk->action = ACTION_CONTINUE; > } > > return ret;