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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 02:28:51 +0300	[thread overview]
Message-ID: <20230523232851.a3djqxmpjyfghbvc@box.shutemov.name> (raw)
In-Reply-To: <2d96a23f-a16a-50e1-7960-a2d4998ce52f@intel.com>

On Tue, May 23, 2023 at 03:43:15PM -0700, Dave Hansen wrote:
> On 5/23/23 15:37, kirill.shutemov@linux.intel.com wrote:
> >> 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.
> 
> We're *eventually* OK:
> 
> >         /* Notify hypervisor that we are about to set/clr encryption attribute. */
> >         x86_platform.guest.enc_status_change_prepare(addr, numpages, enc);
> > 
> >         ret = __change_page_attr_set_clr(&cpa, 1);
> 
> But what about in the middle between enc_status_change_prepare() and
> __change_page_attr_set_clr()?  Don't the direct map and the
> shared/private status of the page diverge in there?

Hmm. Maybe we would need to go through making the range in direct mapping
non-present before notifying VMM about the change.

I need to look at this again in the morning.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

  reply	other threads:[~2023-05-23 23:31 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
2023-05-23 22:43       ` Dave Hansen
2023-05-23 23:28         ` kirill.shutemov [this message]
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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