linux-kernel - Re: [PATCH v10 2/2] x86/tdx: Support vmalloc() for tdx_enc_status

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Message-ID: <e8b1b0b5f32115c0ef8f1aeb0b805c4d9a953b31.camel@intel.com>
Date:   Tue, 5 Sep 2023 16:25:00 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "Jason@...c4.com" <Jason@...c4.com>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "kys@...rosoft.com" <kys@...rosoft.com>,
        "Cui, Dexuan" <decui@...rosoft.com>,
        "nik.borisov@...e.com" <nik.borisov@...e.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "mikelley@...rosoft.com" <mikelley@...rosoft.com>,
        "chu, jane" <jane.chu@...cle.com>, "hpa@...or.com" <hpa@...or.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "bp@...en8.de" <bp@...en8.de>, "Luck, Tony" <tony.luck@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "x86@...nel.org" <x86@...nel.org>
CC:     "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "Li, Xiaoyao" <xiaoyao.li@...el.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Tianyu.Lan@...rosoft.com" <Tianyu.Lan@...rosoft.com>,
        "andavis@...hat.com" <andavis@...hat.com>,
        "mheslin@...hat.com" <mheslin@...hat.com>
Subject: Re: [PATCH v10 2/2] x86/tdx: Support vmalloc() for
 tdx_enc_status_changed()

On Fri, 2023-08-11 at 14:48 -0700, Dexuan Cui wrote:
> When a TDX guest runs on Hyper-V, the hv_netvsc driver's
> netvsc_init_buf()
> allocates buffers using vzalloc(), and needs to share the buffers
> with the
> host OS by calling set_memory_decrypted(), which is not working for
> vmalloc() yet. Add the support by handling the pages one by one.
> 
> Co-developed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
> Reviewed-by: Kuppuswamy Sathyanarayanan
> <sathyanarayanan.kuppuswamy@...ux.intel.com>
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---
>  arch/x86/coco/tdx/tdx.c | 36 ++++++++++++++++++++++++++++++------
>  1 file changed, 30 insertions(+), 6 deletions(-)

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

Only small comment, it is possible to have huge vmalloc's now, which
would mean this would do 512 TDVMCALL_MAP_GPA calls instead of 1 when
encountering a huge vmalloc mapping. If this used lookup_address()
directly instead of slow_virt_to_phys(), it could catch this case. I
don't think there are any cases of huge vmallocs today that would get
passed into set_memory_en/decrypted(), so would only be future
proofing.