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From: Michael Kelley <mikelley@microsoft.com>
To: Tianyu Lan <ltykernel@gmail.com>,
	KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
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Subject: RE: [PATCH V4 08/13] hyperv/vmbus: Initialize VMbus ring buffer for Isolation VM
Date: Thu, 2 Sep 2021 16:14:04 +0000	[thread overview]
Message-ID: <MWHPR21MB1593917C95C95128A4E835D5D7CE9@MWHPR21MB1593.namprd21.prod.outlook.com> (raw)
In-Reply-To: <e864b95d-ecb7-074b-ff0b-85cc451bad52@gmail.com>

From: Tianyu Lan <ltykernel@gmail.com> Sent: Thursday, September 2, 2021 6:36 AM
> 
> On 9/2/2021 8:23 AM, Michael Kelley wrote:
> >> +	} else {
> >> +		pages_wraparound = kcalloc(page_cnt * 2 - 1,
> >> +					   sizeof(struct page *),
> >> +					   GFP_KERNEL);
> >> +
> >> +		pages_wraparound[0] = pages;
> >> +		for (i = 0; i < 2 * (page_cnt - 1); i++)
> >> +			pages_wraparound[i + 1] =
> >> +				&pages[i % (page_cnt - 1) + 1];
> >> +
> >> +		ring_info->ring_buffer = (struct hv_ring_buffer *)
> >> +			vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
> >> +				PAGE_KERNEL);
> >> +
> >> +		kfree(pages_wraparound);
> >> +		if (!ring_info->ring_buffer)
> >> +			return -ENOMEM;
> >> +	}
> > With this patch, the code is a big "if" statement with two halves -- one
> > when SNP isolation is in effect, and the other when not.  The SNP isolation
> > case does the work using PFNs with the shared_gpa_boundary added,
> > while the other case does the same work but using struct page.  Perhaps
> > I'm missing something, but can both halves be combined and always
> > do the work using PFNs?  The only difference is whether to add the
> > shared_gpa_boundary, and whether to zero the memory when done.
> > So get the starting PFN, then have an "if" statement for whether to
> > add the shared_gpa_boundary.  Then everything else is the same.
> > At the end, use an "if" statement to decide whether to zero the
> > memory.  It would really be better to have the logic in this algorithm
> > coded only once.
> >
> 
> Hi Michael:
> 	I have tried this before. But vmap_pfn() only works for those pfns out
> of normal memory. Please see vmap_pfn_apply() for detail and
> return error when the PFN is valid.
> 

Indeed.  This ties into the discussion with Christoph about coming up
with generalized helper functions to assist in handling the
shared_gpa_boundary.   Having a single implementation here in
hv_ringbuffer_init() would be a good goal as well.

Michael


  reply	other threads:[~2021-09-02 16:30 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-27 17:20 [PATCH V4 00/13] x86/Hyper-V: Add Hyper-V Isolation VM support Tianyu Lan
2021-08-27 17:20 ` [PATCH V4 01/13] x86/hyperv: Initialize GHCB page in Isolation VM Tianyu Lan
2021-09-02  0:15   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 02/13] x86/hyperv: Initialize shared memory boundary in the " Tianyu Lan
2021-09-02  0:15   ` Michael Kelley
2021-09-02  6:35     ` Tianyu Lan
2021-08-27 17:21 ` [PATCH V4 03/13] x86/hyperv: Add new hvcall guest address host visibility support Tianyu Lan
2021-09-02  0:16   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 04/13] hyperv: Mark vmbus ring buffer visible to host in Isolation VM Tianyu Lan
2021-08-27 17:41   ` Greg KH
2021-08-27 17:44     ` Tianyu Lan
2021-09-02  0:17   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 05/13] hyperv: Add Write/Read MSR registers via ghcb page Tianyu Lan
2021-08-27 17:41   ` Greg KH
2021-08-27 17:46     ` Tianyu Lan
2021-09-02  3:32   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 06/13] hyperv: Add ghcb hvcall support for SNP VM Tianyu Lan
2021-09-02  0:20   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 07/13] hyperv/Vmbus: Add SNP support for VMbus channel initiate message Tianyu Lan
2021-09-02  0:21   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 08/13] hyperv/vmbus: Initialize VMbus ring buffer for Isolation VM Tianyu Lan
2021-09-02  0:23   ` Michael Kelley
2021-09-02 13:35     ` Tianyu Lan
2021-09-02 16:14       ` Michael Kelley [this message]
2021-08-27 17:21 ` [PATCH V4 09/13] DMA: Add dma_map_decrypted/dma_unmap_encrypted() function Tianyu Lan
2021-08-27 17:21 ` [PATCH V4 10/13] x86/Swiotlb: Add Swiotlb bounce buffer remap function for HV IVM Tianyu Lan
2021-08-27 17:21 ` [PATCH V4 11/13] hyperv/IOMMU: Enable swiotlb bounce buffer for Isolation VM Tianyu Lan
2021-09-02  1:27   ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 12/13] hv_netvsc: Add Isolation VM support for netvsc driver Tianyu Lan
2021-09-02  2:34   ` Michael Kelley
2021-09-02  4:56     ` Michael Kelley
2021-08-27 17:21 ` [PATCH V4 13/13] hv_storvsc: Add Isolation VM support for storvsc driver Tianyu Lan
2021-09-02  2:08   ` Michael Kelley
2021-08-30 12:00 ` [PATCH V4 00/13] x86/Hyper-V: Add Hyper-V Isolation VM support Christoph Hellwig
2021-08-31 15:20   ` Tianyu Lan
2021-09-02  7:51     ` Christoph Hellwig
2021-08-31 17:16   ` Michael Kelley
2021-09-02  7:59     ` Christoph Hellwig
2021-09-02 11:21       ` Tianyu Lan
2021-09-02 15:57       ` Michael Kelley
2021-09-14 14:41         ` Tianyu Lan

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