From: Nadav Amit <nadav.amit@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
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 09:29:09 -0700 [thread overview]
Message-ID: <F5E4E2C2-5F1C-42AC-8707-0D0B8C00D251@gmail.com> (raw)
In-Reply-To: <YXaMaUbdDOxMTstc@hirez.programming.kicks-ass.net>
> On Oct 25, 2021, at 3:52 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> 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?
Yes. Of course. Where did my code go to? :(
>
>> +}
>> +
>> /*
>> * 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.
I tried to start a new trend. I will fix it.
>
>> */
>> - 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() ?
> */
I will add a comment.
next prev parent reply other threads:[~2021-10-25 16:29 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
2021-10-25 16:29 ` Nadav Amit [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=F5E4E2C2-5F1C-42AC-8707-0D0B8C00D251@gmail.com \
--to=nadav.amit@gmail.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=andrew.cooper3@citrix.com \
--cc=dave.hansen@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=npiggin@gmail.com \
--cc=peterx@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=will@kernel.org \
--cc=x86@kernel.org \
--cc=yuzhao@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).