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Thu, 2 Mar 2023 21:11:25 GMT Received: from smtpav02.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2CD965805F; Thu, 2 Mar 2023 21:11:25 +0000 (GMT) Received: from smtpav02.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 737F05805B; Thu, 2 Mar 2023 21:11:15 +0000 (GMT) Received: from [9.65.199.252] (unknown [9.65.199.252]) by smtpav02.wdc07v.mail.ibm.com (Postfix) with ESMTP; Thu, 2 Mar 2023 21:11:15 +0000 (GMT) Message-ID: <740d3ee7-e981-0812-f21e-296a7f350388@linux.ibm.com> Date: Thu, 2 Mar 2023 23:11:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH RFC v8 52/56] ccp: Add support to decrypt the page Content-Language: en-US To: Tom Lendacky , Zhi Wang , Michael Roth Cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, jroedel@suse.de, hpa@zytor.com, ardb@kernel.org, pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com, jmattson@google.com, luto@kernel.org, dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com, peterz@infradead.org, srinivas.pandruvada@linux.intel.com, rientjes@google.com, tobin@ibm.com, bp@alien8.de, vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com, tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com, dgilbert@redhat.com, jarkko@kernel.org, ashish.kalra@amd.com, nikunj.dadhania@amd.com, Brijesh Singh , Dov Murik References: <20230220183847.59159-1-michael.roth@amd.com> <20230220183847.59159-53-michael.roth@amd.com> <20230301232045.0000502e@intel.com> <36734887-6474-b43e-51ae-34f37e6670a5@amd.com> From: Dov Murik In-Reply-To: <36734887-6474-b43e-51ae-34f37e6670a5@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: BH9z6nn2n8lzIHVH_MLBi3cktElaaSB7 X-Proofpoint-ORIG-GUID: NKQS8NB6-1CcXMFAavhlGNyyCSi2rGOZ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-03-02_13,2023-03-02_02,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 clxscore=1015 lowpriorityscore=0 malwarescore=0 suspectscore=0 priorityscore=1501 adultscore=0 bulkscore=0 mlxscore=0 spamscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2303020182 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: B24CC40004 X-Stat-Signature: otnsgjh3kyjzptu4h386t9xcjkospnbt X-HE-Tag: 1677791508-973700 X-HE-Meta: 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 QdYx4eOz /YB5MI8zFx7vbc+uJZshAI9L7tQvhs0SZLvY0F7hHVANKHnxEhWUCELU/coqKNIRTJTT6kEW1RY0l193H/9cMmtkIYew3q0F/iivxrT1x7tSvx7nUiMjYzaQS60DqCdinqO99EWETqR8GXPbSKpMrGjKJgptWCw8lF/CrefV6Ra8xRhlK29+d4rSx4JLUetPML36a07VlADFqgKAoSYQ1YVrtxM7l/FbImscbs3Zn6WOmPM1gCmCg4SIdcg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 02/03/2023 16:33, Tom Lendacky wrote: > On 3/1/23 23:59, Dov Murik wrote: >> Hi Mike, Zhi, >> >> On 01/03/2023 23:20, Zhi Wang wrote: >>> On Mon, 20 Feb 2023 12:38:43 -0600 >>> Michael Roth wrote: >>> >>>> From: Brijesh Singh >>>> >>>> Add support to decrypt guest encrypted memory. These API interfaces can >>>> be used for example to dump VMCBs on SNP guest exit. >>>> >>> >>> What kinds of check will be applied from firmware when VMM decrypts this >>> page? I suppose there has to be kinda mechanism to prevent VMM to >>> decrypt >>> any page in the guest. It would be nice to have some introduction about >>> it in the comments. >>> >> >> The SNP ABI spec says (section 8.27.2 SNP_DBG_DECRYPT): >> >>    The firmware checks that the guest's policy allows debugging. If not, >>    the firmware returns POLICY_FAILURE. >> >> and in the Guest Policy (section 4.3): >> >>    Bit 19 - DEBUG >>    0: Debugging is disallowed. >>    1: Debugging is allowed. >> >> In the kernel, that firmware error code is defined as >> SEV_RET_POLICY_FAILURE. >> >> >>>> Signed-off-by: Brijesh Singh >>>> Signed-off-by: Ashish Kalra >>>> [mdr: minor commit fixups] >>>> Signed-off-by: Michael Roth >>>> --- >>>>   drivers/crypto/ccp/sev-dev.c | 32 ++++++++++++++++++++++++++++++++ >>>>   include/linux/psp-sev.h      | 22 ++++++++++++++++++++-- >>>>   2 files changed, 52 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/crypto/ccp/sev-dev.c >>>> b/drivers/crypto/ccp/sev-dev.c >>>> index e65563bc8298..bf5167b2acfc 100644 >>>> --- a/drivers/crypto/ccp/sev-dev.c >>>> +++ b/drivers/crypto/ccp/sev-dev.c >>>> @@ -2017,6 +2017,38 @@ int sev_guest_df_flush(int *error) >>>>   } >>>>   EXPORT_SYMBOL_GPL(sev_guest_df_flush); >>>>   +int snp_guest_dbg_decrypt_page(u64 gctx_pfn, u64 src_pfn, u64 >>>> dst_pfn, int *error) >>>> +{ >>>> +    struct sev_data_snp_dbg data = {0}; >>>> +    struct sev_device *sev; >>>> +    int ret; >>>> + >>>> +    if (!psp_master || !psp_master->sev_data) >>>> +        return -ENODEV; >>>> + >>>> +    sev = psp_master->sev_data; >>>> + >>>> +    if (!sev->snp_initialized) >>>> +        return -EINVAL; >>>> + >>>> +    data.gctx_paddr = sme_me_mask | (gctx_pfn << PAGE_SHIFT); >>>> +    data.src_addr = sme_me_mask | (src_pfn << PAGE_SHIFT); >>>> +    data.dst_addr = sme_me_mask | (dst_pfn << PAGE_SHIFT); >> >> I guess this works, but I wonder why we need to turn on sme_me_mask on >> teh dst_addr.  I thought that the firmware decrypts the guest page >> (src_addr) to a plaintext page.  Couldn't find this requirement in the >> SNP spec. > > This sme_me_mask tells the firmware how to access the host memory > (similar to how DMA uses sme_me_mask when supplying addresses to devices > under SME). This needs to match the pagetable mapping being used by the > host, otherwise the contents will appears as ciphertext to the host if > they are not in sync. Since the default pagetable mapping is encrypted, > the sme_me_mask bit must be provided on the destination address. So it > is not a spec requirement, but an SME implementation requirement. > Ah, OK, that's clear now. Thanks Tom. -Dov