linux-kernel - Re: [PATCH v5 3/8] arm64: hyperv: Add memory alloc/free functions for Hyper-V size pages

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Message-ID: <43d53ebd2637bd9106137103028a4f0e@www.loen.fr>
Date:   Thu, 07 Nov 2019 15:28:49 +0109
From:   Marc Zyngier <maz@...nel.org>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     <will@...nel.org>, <catalin.marinas@....com>,
        <mark.rutland@....com>, <linux-arm-kernel@...ts.infradead.org>,
        <gregkh@...uxfoundation.org>, <linux-kernel@...r.kernel.org>,
        <linux-hyperv@...r.kernel.org>, <devel@...uxdriverproject.org>,
        <olaf@...fle.de>, <apw@...onical.com>,
        vkuznets <vkuznets@...hat.com>, <jasowang@...hat.com>,
        <marcelo.cerri@...onical.com>, KY Srinivasan <kys@...rosoft.com>,
        Sunil Muthuswamy <sunilmut@...rosoft.com>,
        "boqun.feng" <boqun.feng@...il.com>
Subject: Re: [PATCH v5 3/8] arm64: hyperv: Add memory alloc/free functions  for Hyper-V size pages

On 2019-10-03 20:12, Michael Kelley wrote:
> Add ARM64-specific code to allocate memory with HV_HYP_PAGE_SIZE
> size and alignment. These are for use when pages need to be shared
> with Hyper-V. Separate functions are needed as the page size used
> by Hyper-V may not be the same as the guest page size.  Free
> operations are rarely done, so no attempt is made to combine
> freed pages into larger chunks.
>
> This code is built only when CONFIG_HYPERV is enabled.
>
> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
> ---
>  arch/arm64/hyperv/hv_init.c    | 68
> ++++++++++++++++++++++++++++++++++++++++++
>  include/asm-generic/mshyperv.h |  5 ++++
>  2 files changed, 73 insertions(+)
>
> diff --git a/arch/arm64/hyperv/hv_init.c 
> b/arch/arm64/hyperv/hv_init.c
> index 6808bc8..9c294f6 100644
> --- a/arch/arm64/hyperv/hv_init.c
> +++ b/arch/arm64/hyperv/hv_init.c
> @@ -15,10 +15,78 @@
>  #include <linux/export.h>
>  #include <linux/mm.h>
>  #include <linux/hyperv.h>
> +#include <linux/spinlock.h>
> +#include <linux/list.h>
> +#include <linux/string.h>
>  #include <asm-generic/bug.h>
>  #include <asm/hyperv-tlfs.h>
>  #include <asm/mshyperv.h>
>
> +
> +/*
> + * Functions for allocating and freeing memory with size and
> + * alignment HV_HYP_PAGE_SIZE. These functions are needed because
> + * the guest page size may not be the same as the Hyper-V page
> + * size. And while kalloc() could allocate the memory, it does not
> + * guarantee the required alignment. So a separate small memory
> + * allocator is needed.  The free function is rarely used, so it
> + * does not try to combine freed pages into larger chunks.

Is this still needed now that kmalloc has alignment guarantees
(see 59bb47985c1d)?

         M.
-- 
Jazz is not dead. It just smells funny...