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From: kirill.shutemov@linux.intel.com
To: Dave Hansen <dave.hansen@intel.com>
Cc: Dexuan Cui <decui@microsoft.com>,
	ak@linux.intel.com, arnd@arndb.de, bp@alien8.de,
	brijesh.singh@amd.com, dan.j.williams@intel.com,
	dave.hansen@linux.intel.com, haiyangz@microsoft.com,
	hpa@zytor.com, jane.chu@oracle.com, kys@microsoft.com,
	linux-arch@vger.kernel.org, linux-hyperv@vger.kernel.org,
	luto@kernel.org, mingo@redhat.com, peterz@infradead.org,
	rostedt@goodmis.org, sathyanarayanan.kuppuswamy@linux.intel.com,
	seanjc@google.com, tglx@linutronix.de, tony.luck@intel.com,
	wei.liu@kernel.org, x86@kernel.org, mikelley@microsoft.com,
	linux-kernel@vger.kernel.org, Tianyu.Lan@microsoft.com
Subject: Re: [PATCH v6 2/6] x86/tdx: Support vmalloc() for tdx_enc_status_changed()
Date: Wed, 24 May 2023 01:37:50 +0300	[thread overview]
Message-ID: <20230523223750.botogigv6ht7p2zg@box.shutemov.name> (raw)
In-Reply-To: <9e466079-ff27-f928-b470-eb5ef157f048@intel.com>

On Tue, May 23, 2023 at 01:39:11PM -0700, Dave Hansen wrote:
> On 5/4/23 15:53, 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.
> 
> I think this sets a bad precedent.
> 
> There are consequences for converting pages between shared and private.
> Doing it on a vmalloc() mapping is guaranteed to fracture the underlying
> EPT/SEPT mappings.
> 
> How does this work with load_unaligned_zeropad()?  Couldn't it be
> running around poking at one of these vmalloc()'d pages via the direct
> map during a shared->private conversion before the page has been accepted?

Alias processing in __change_page_attr_set_clr() will change direct
mapping if you call it on vmalloc()ed memory. I think we are safe wrt
load_unaligned_zeropad() here.
-- 
  Kiryl Shutsemau / Kirill A. Shutemov

  parent reply	other threads:[~2023-05-23 22:38 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-04 22:53 [PATCH v6 0/6] Support TDX guests on Hyper-V Dexuan Cui
2023-05-04 22:53 ` [PATCH v6 1/6] x86/tdx: Retry TDVMCALL_MAP_GPA() when needed Dexuan Cui
2023-05-23 21:13   ` Dave Hansen
2023-05-25  2:06     ` Dexuan Cui
2023-05-04 22:53 ` [PATCH v6 2/6] x86/tdx: Support vmalloc() for tdx_enc_status_changed() Dexuan Cui
2023-05-23 20:39   ` Dave Hansen
2023-05-23 21:25     ` Sean Christopherson
2023-05-23 21:33       ` Dave Hansen
2023-05-23 23:02         ` Edgecombe, Rick P
2023-05-23 22:37     ` kirill.shutemov [this message]
2023-05-23 22:43       ` Dave Hansen
2023-05-23 23:28         ` kirill.shutemov
2023-05-25 19:08           ` Kirill A. Shutemov
2023-05-25 19:18             ` Dave Hansen
2023-05-04 22:53 ` [PATCH v6 3/6] x86/hyperv: Add hv_isolation_type_tdx() to detect TDX guests Dexuan Cui
2023-05-04 22:53 ` [PATCH v6 4/6] x86/hyperv: Support hypercalls for " Dexuan Cui
2023-05-04 22:53 ` [PATCH v6 5/6] Drivers: hv: vmbus: Support " Dexuan Cui
2023-05-05 16:22   ` Michael Kelley (LINUX)
2023-05-05 16:48     ` Dexuan Cui
2023-05-04 22:53 ` [PATCH v6 6/6] x86/hyperv: Fix serial console interrupts for " Dexuan Cui
2023-05-23 19:24 ` [PATCH v6 0/6] Support TDX guests on Hyper-V Dexuan Cui

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