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SubjectRe: [RFC PATCH V2 08/18] x86/hyperv: decrypt vmbus pages for sev-snp enlightened guest
From
On 12/14/2022 2:08 AM, Michael Kelley (LINUX) wrote:
> From: Tianyu Lan <ltykernel@gmail.com> Sent: Friday, November 18, 2022 7:46 PM
>>
>
> The Subject prefix for this patch should be "Drivers: hv: vmbus:"

Sure. Will update in the next version.

>
>> Vmbus int, synic and post message pages are shared with hypervisor
>> and so decrypt these pages in the sev-snp guest.
>>
>> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
>> ---
>> drivers/hv/connection.c | 13 +++++++++++++
>> drivers/hv/hv.c | 32 +++++++++++++++++++++++++++++++-
>> 2 files changed, 44 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
>> index 9dc27e5d367a..43141225ea15 100644
>> --- a/drivers/hv/connection.c
>> +++ b/drivers/hv/connection.c
>> @@ -215,6 +215,15 @@ int vmbus_connect(void)
>> (void *)((unsigned long)vmbus_connection.int_page +
>> (HV_HYP_PAGE_SIZE >> 1));
>>
>> + if (hv_isolation_type_snp() || hv_isolation_type_en_snp()) {
>
> This decryption should be done only for a fully enlightened SEV-SNP
> guest, not for a vTOM guest.
>
>> + ret = set_memory_decrypted((unsigned long)
>> + vmbus_connection.int_page, 1);
>> + if (ret)
>> + goto cleanup;
>
> This cleanup path doesn't work correctly. It calls
> vmbus_disconnect(), which will try to re-encrypt the memory.
> But if the original decryption failed, re-encrypting is the wrong
> thing to do.
>
> It looks like this same bug exists in current code if the decryption
> of the monitor pages fails or if just one of the original memory
> allocations fails. vmbus_disconnect() doesn't know whether it
> should re-encrypt the pages.

Agree. It's necessary to handle decryption failure case by case in stead
of re-encryting all pages. Will fix this in the next version. Thanks to
point out.

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