linux-kernel - Re: [PATCH v4 2/3] arm64: Implement page table free interfaces

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Message-ID: <b5427cbd-28f8-e561-cfca-751006e60da1@codeaurora.org>
Date:   Tue, 27 Mar 2018 10:08:02 +0530
From:   Chintan Pandya <cpandya@...eaurora.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     catalin.marinas@....com, will.deacon@....com, arnd@...db.de,
        ard.biesheuvel@...aro.org, marc.zyngier@....com,
        james.morse@....com, kristina.martsenko@....com,
        takahiro.akashi@...aro.org, gregkh@...uxfoundation.org,
        tglx@...utronix.de, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        akpm@...ux-foundation.org, toshi.kani@....com
Subject: Re: [PATCH v4 2/3] arm64: Implement page table free interfaces



On 3/26/2018 3:25 PM, Mark Rutland wrote:
> On Tue, Mar 20, 2018 at 05:15:13PM +0530, Chintan Pandya wrote:
>> +static int __pmd_free_pte_page(pmd_t *pmd, unsigned long addr, bool tlb_inv)
>> +{
>> +	pmd_t *table;
>> +
>> +	if (pmd_val(*pmd)) {
>> +		table = __va(pmd_val(*pmd));
>> +		pmd_clear(pmd);
>> +		/*
>> +		 * FIXME: __flush_tlb_pgtable(&init_mm, addr) is
>> +		 *        ideal candidate here, which exactly
>> +		 *        flushes intermediate pgtables. But,
>> +		 *        this is broken (evident from tests).
>> +		 *        So, use safe TLB op unless that is fixed.
>> +		 */
>> +		if (tlb_inv)
>> +			flush_tlb_kernel_range(addr, addr + PMD_SIZE);
> 
> I don't think that __flush_tlb_pgtable() is broken. It's only valid to
> call it for user page tables, since it doesn't affect all ASIDs.
> 
> We can add a simlar helper for kernel mappings, which affects all ASIDs,
> e.g.
> 
Okay. I will test it and update v5.

> static inline void __flush_tlb_kernel_pgtable(unsigned long addr)
> {
> 	addr >>= 12;
> 	__tlbi(vaae1is, addr);
> 	dsb(ish);
> }
> 
> Thanks,
> Mark.
> 

Chintan
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