From: Peter Zijlstra <peterz@infradead.org>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Nadav Amit <namit@vmware.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Xu <peterx@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>, Yu Zhao <yuzhao@google.com>,
Nick Piggin <npiggin@gmail.com>,
x86@kernel.org
Subject: Re: [PATCH v2 2/5] mm: avoid unnecessary flush on change_huge_pmd()
Date: Mon, 25 Oct 2021 12:52:25 +0200 [thread overview]
Message-ID: <YXaMaUbdDOxMTstc@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20211021122112.592634-3-namit@vmware.com>
On Thu, Oct 21, 2021 at 05:21:09AM -0700, Nadav Amit wrote:
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> index 448cd01eb3ec..18c3366f8f4d 100644
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -1146,6 +1146,14 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
> }
> }
> #endif
> +
> +#define __HAVE_ARCH_PMDP_INVALIDATE_AD
> +static inline pmd_t pmdp_invalidate_ad(struct vm_area_struct *vma,
> + unsigned long address, pmd_t *pmdp)
> +{
> + return pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp));
Did this want to be something like:
pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp));
if (cpu_feature_enabled(X86_BUG_PTE_LEAK))
flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
return old;
instead?
> +}
> +
> /*
> * Page table pages are page-aligned. The lower half of the top
> * level is used for userspace and the top half for the kernel.
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index e5ea5f775d5c..435da011b1a2 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1795,10 +1795,11 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
> * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
> * which may break userspace.
> *
> - * pmdp_invalidate() is required to make sure we don't miss
> - * dirty/young flags set by hardware.
> + * pmdp_invalidate_ad() is required to make sure we don't miss
> + * dirty/young flags (which are also known as access/dirty) cannot be
> + * further modifeid by the hardware.
"modified", I think is the more common spelling.
> */
> - entry = pmdp_invalidate(vma, addr, pmd);
> + entry = pmdp_invalidate_ad(vma, addr, pmd);
>
> entry = pmd_modify(entry, newprot);
> if (preserve_write)
> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
> index 4e640baf9794..b0ce6c7391bf 100644
> --- a/mm/pgtable-generic.c
> +++ b/mm/pgtable-generic.c
> @@ -200,6 +200,14 @@ pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
> }
> #endif
>
> +#ifndef __HAVE_ARCH_PMDP_INVALIDATE_AD
/*
* Does this deserve a comment to explain the intended difference vs
* pmdp_invalidate() ?
*/
> +pmd_t pmdp_invalidate_ad(struct vm_area_struct *vma, unsigned long address,
> + pmd_t *pmdp)
> +{
> + return pmdp_invalidate(vma, address, pmdp);
> +}
> +#endif
> +
> #ifndef pmdp_collapse_flush
> pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
> pmd_t *pmdp)
> --
> 2.25.1
>
next prev parent reply other threads:[~2021-10-25 10:52 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-21 12:21 [PATCH v2 0/5] mm/mprotect: avoid unnecessary TLB flushes Nadav Amit
2021-10-21 12:21 ` [PATCH v2 1/5] x86: Detection of Knights Landing A/D leak Nadav Amit
2021-10-26 15:54 ` Dave Hansen
2021-10-26 15:57 ` Nadav Amit
2021-10-21 12:21 ` [PATCH v2 2/5] mm: avoid unnecessary flush on change_huge_pmd() Nadav Amit
2021-10-25 10:52 ` Peter Zijlstra [this message]
2021-10-25 16:29 ` Nadav Amit
2021-10-26 16:06 ` Dave Hansen
2021-10-26 16:47 ` Nadav Amit
2021-10-26 16:53 ` Nadav Amit
2021-10-26 17:44 ` Nadav Amit
2021-10-26 18:44 ` Dave Hansen
2021-10-26 19:06 ` Nadav Amit
2021-10-26 19:40 ` Dave Hansen
2021-10-26 20:07 ` Nadav Amit
2021-10-26 20:47 ` Dave Hansen
2021-10-21 12:21 ` [PATCH v2 3/5] x86/mm: check exec permissions on fault Nadav Amit
2021-10-25 10:59 ` Peter Zijlstra
2021-10-25 11:13 ` Andrew Cooper
2021-10-25 14:23 ` Dave Hansen
2021-10-25 14:20 ` Dave Hansen
2021-10-25 16:19 ` Nadav Amit
2021-10-25 17:45 ` Dave Hansen
2021-10-25 17:51 ` Nadav Amit
2021-10-25 18:00 ` Dave Hansen
2021-10-21 12:21 ` [PATCH v2 4/5] mm/mprotect: use mmu_gather Nadav Amit
2021-10-21 12:21 ` [PATCH v2 5/5] mm/mprotect: do not flush on permission promotion Nadav Amit
2021-10-25 11:12 ` Peter Zijlstra
2021-10-25 16:27 ` Nadav Amit
2021-10-22 3:04 ` [PATCH v2 0/5] mm/mprotect: avoid unnecessary TLB flushes Andrew Morton
2021-10-22 21:58 ` Nadav Amit
2021-10-26 16:09 ` Dave Hansen
2021-10-25 10:50 ` Peter Zijlstra
2021-10-25 16:42 ` Nadav Amit
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