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From: Brijesh Singh <brijesh.singh@amd.com>
To: Sean Christopherson <seanjc@google.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: brijesh.singh@amd.com, Paolo Bonzini <pbonzini@redhat.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	John Allen <john.allen@amd.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-crypto@vger.kernel.org,
	linux-kernel@vger.kernel.org, Borislav Petkov <bp@suse.de>
Subject: Re: [PATCH 3/5] crypto: ccp: Play nice with vmalloc'd memory for SEV command structs
Date: Mon, 5 Apr 2021 11:01:20 -0500
Message-ID: <72d52bd3-453c-e6fa-4209-e2296ee34829@amd.com> (raw)
In-Reply-To: <YGsnjqFLoqXTrAHo@google.com>


On 4/5/21 10:06 AM, Sean Christopherson wrote:
> On Sun, Apr 04, 2021, Christophe Leroy wrote:
>> Le 03/04/2021 à 01:37, Sean Christopherson a écrit :
>>> @@ -152,11 +153,21 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>>>   	sev = psp->sev_data;
>>>   	buf_len = sev_cmd_buffer_len(cmd);
>>> -	if (WARN_ON_ONCE(!!data != !!buf_len))
>>> +	if (WARN_ON_ONCE(!!__data != !!buf_len))
>>>   		return -EINVAL;
>>> -	if (WARN_ON_ONCE(data && is_vmalloc_addr(data)))
>>> -		return -EINVAL;
>>> +	if (__data && is_vmalloc_addr(__data)) {
>>> +		/*
>>> +		 * If the incoming buffer is virtually allocated, copy it to
>>> +		 * the driver's scratch buffer as __pa() will not work for such
>>> +		 * addresses, vmalloc_to_page() is not guaranteed to succeed,
>>> +		 * and vmalloc'd data may not be physically contiguous.
>>> +		 */
>>> +		data = sev->cmd_buf;
>>> +		memcpy(data, __data, buf_len);
>>> +	} else {
>>> +		data = __data;
>>> +	}
>> I don't know how big commands are, but if they are small, it would probably
>> be more efficient to inconditionnally copy them to the buffer rather then
>> doing the test.
> Brijesh, I assume SNP support will need to copy the commands unconditionally? If
> yes, it probably makes sense to do so now and avoid vmalloc dependencies
> completely.  And I think that would allow for the removal of status_cmd_buf and
> init_cmd_buf, or is there another reason those dedicated buffers exist?


Yes, we need to copy the commands unconditionally for the SNP support.
It makes sense to avoid the vmalloc dependencies. I can't think of any
reason why we would need the status_cmd_buf and init_cmd_buf after those
changes.



  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-02 23:36 [PATCH 0/5] ccp: KVM: SVM: Use stack for SEV command buffers Sean Christopherson
2021-04-02 23:36 ` [PATCH 1/5] crypto: ccp: Detect and reject vmalloc addresses destined for PSP Sean Christopherson
2021-04-04  6:31   ` Christophe Leroy
2021-04-02 23:36 ` [PATCH 2/5] crypto: ccp: Reject SEV commands with mismatching command buffer Sean Christopherson
2021-04-03 17:02   ` Christophe Leroy
2021-04-05 16:26   ` Tom Lendacky
2021-04-05 16:33     ` Sean Christopherson
2021-04-05 16:37       ` Tom Lendacky
2021-04-02 23:37 ` [PATCH 3/5] crypto: ccp: Play nice with vmalloc'd memory for SEV command structs Sean Christopherson
2021-04-03 17:05   ` Christophe Leroy
2021-04-03 17:13   ` Christophe Leroy
2021-04-04  6:48   ` Christophe Leroy
2021-04-05 15:06     ` Sean Christopherson
2021-04-05 16:01       ` Brijesh Singh [this message]
2021-04-02 23:37 ` [PATCH 4/5] crypto: ccp: Use the stack for small SEV command buffers Sean Christopherson
2021-04-02 23:37 ` [PATCH 5/5] KVM: SVM: Allocate SEV command structures on local stack Sean Christopherson
2021-04-04 19:54 ` [PATCH 0/5] ccp: KVM: SVM: Use stack for SEV command buffers Brijesh Singh

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