linux-kernel - Re: [PATCH v2 1/1] swiotlb: do not free decrypted pages if dynamic

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Message-ID: <e0129428bc80f9deaf7a6852007d48103e133e27.camel@intel.com>
Date:   Thu, 2 Nov 2023 15:57:55 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "robin.murphy@....com" <robin.murphy@....com>,
        "hch@....de" <hch@....de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "patchwork@...wei.com" <patchwork@...wei.com>,
        "petrtesarik@...weicloud.com" <petrtesarik@...weicloud.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "petr.tesarik1@...wei-partners.com" 
        <petr.tesarik1@...wei-partners.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "miaoxie@...wei.com" <miaoxie@...wei.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "guohanjun@...wei.com" <guohanjun@...wei.com>,
        "leijitang@...wei.com" <leijitang@...wei.com>,
        "weiyongjun1@...wei.com" <weiyongjun1@...wei.com>,
        "huawei.libin@...wei.com" <huawei.libin@...wei.com>,
        "wangkefeng.wang@...wei.com" <wangkefeng.wang@...wei.com>,
        "linuxarm@...wei.com" <linuxarm@...wei.com>,
        "johnny.chenyi@...wei.com" <johnny.chenyi@...wei.com>,
        "yuehaibing@...wei.com" <yuehaibing@...wei.com>,
        "petr@...arici.cz" <petr@...arici.cz>,
        "roberto.sassu@...weicloud.com" <roberto.sassu@...weicloud.com>,
        "ming.fu@...wei.com" <ming.fu@...wei.com>,
        "zhujianwei7@...wei.com" <zhujianwei7@...wei.com>
Subject: Re: [PATCH v2 1/1] swiotlb: do not free decrypted pages if dynamic

On Thu, 2023-11-02 at 10:36 +0100, Petr Tesarik wrote:
> +       vaddr = phys_to_virt(paddr);
>         if (set_memory_decrypted((unsigned long)vaddr,
> PFN_UP(bytes)))
>                 goto error;
>         return page;
>  
>  error:
> -       __free_pages(page, order);
> +       /* Intentional leak if pages cannot be encrypted again. */
> +       if (!set_memory_encrypted((unsigned long)vaddr,
> PFN_UP(bytes)))
> +               __free_pages(page, order);
>         return NULL;
>  }

My patch was going to just leak the pages if set_memory_decrypted()
fails, and not try to re-encrypt. It didn't seem worth the extra logic
for the rare case. But this works too.

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>