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Thu, 12 Nov 2026 16:46:17 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 040C620B7166 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1794530778; bh=1vBgOZighXGOllRdyE42732n3hMUT8k/mfbvblMTQQA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Dt/E76kI/3MFpUYYHZOURgy6EkuaTi8S8z5ncW2I/9sTmvxARptIu+vmDL6Tjc4IN 5gSmEOJ0Q1EPS7g1x//7jcGiliU1FVjk8KiQarz3eBVAdpjIXlT/6b+rBBy3Gmi2m7 yhwafN52I0kemUkmW8gkwXEyUvkufDSSAKcNQa9U= Message-ID: Date: Thu, 12 Nov 2026 16:46:21 -0800 X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.13.1 Subject: Re: [PATCH v6 4/6] Drivers: hv: Mark shared memory as decrypted for CCA Realms Content-Language: en-US To: Kameron Carr Cc: Michael Kelley , "decui@microsoft.com" , "haiyangz@microsoft.com" , "wei.liu@kernel.org" , "arnd@arndb.de" , "catalin.marinas@arm.com" , "linux-arch@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-hyperv@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "lpieralisi@kernel.org" , "mark.rutland@arm.com" , "sudeep.holla@kernel.org" , "thuth@redhat.com" , "will@kernel.org" References: <20261031001412.4150488-1-kameroncarr@linux.microsoft.com> <20261031001412.4150488-5-kameroncarr@linux.microsoft.com> From: Mukesh R In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/12/26 09:49, Kameron Carr wrote: > On 11/11/2026 6:43 PM, Mukesh R wrote: >> On 11/11/26 10:01, Michael Kelley wrote: >>> From: Kameron Carr Sent: Friday, October 30, 2026 5:14 PM >>>> >>>> In hv_common_cpu_init(), the per-CPU hypercall input/output pages need >>>> to be marked as decrypted (shared) for confidential VM isolation types. >>>> This is already done for SNP and TDX isolation; extend the same handling >>>> to Arm CCA Realm guests so that the host hypervisor can access the >>>> shared hypercall buffers. >>>> >>>> is_realm_world() is declared in include/linux/arm-rsi-cmds.h which only >>>> builds on arm64 (it includes ), so using it directly in >>>> the arch-neutral drivers/hv/hv_common.c would break the x86 build. >>>> Introduce a Hyper-V-specific helper following the established >>>> hv_isolation_type_snp() / hv_isolation_type_tdx() pattern. >>>> >>>> On architectures other than arm64 the weak default keeps the existing >>>> behaviour. >>>> >>>> Reviewed-by: Michael Kelley >>>> Signed-off-by: Kameron Carr >>>> --- >>>> arch/arm64/hyperv/mshyperv.c | 5 +++++ >>>> drivers/hv/hv_common.c | 17 +++++++++++++---- >>>> include/asm-generic/mshyperv.h | 1 + >>>> 3 files changed, 19 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c >>>> index 46ab2da..da6c3aa0 100644 >>>> --- a/arch/arm64/hyperv/mshyperv.c >>>> +++ b/arch/arm64/hyperv/mshyperv.c >>>> @@ -182,3 +182,8 @@ bool hv_is_hyperv_initialized(void) >>>> return hyperv_initialized; >>>> } >>>> EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized); >>>> + >>>> +bool hv_isolation_type_cca(void) >>>> +{ >>>> + return is_realm_world(); >>>> +} >>>> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c >>>> index 31256cb..a60c92c 100644 >>>> --- a/drivers/hv/hv_common.c >>>> +++ b/drivers/hv/hv_common.c >>>> @@ -476,6 +476,7 @@ int hv_common_cpu_init(unsigned int cpu) >>>> u64 msr_vp_index; >>>> gfp_t flags; >>>> const int pgcount = hv_output_page_exists() ? 2 : 1; >>>> + const size_t alloc_size = ALIGN((size_t)pgcount * HV_HYP_PAGE_SIZE, PAGE_SIZE); >>>> void *mem; >>>> int ret = 0; >>>> >>>> @@ -489,7 +490,7 @@ int hv_common_cpu_init(unsigned int cpu) >>>> * online and then taken offline >>>> */ >>>> if (!*inputarg) { >>>> - mem = kmalloc_array(pgcount, HV_HYP_PAGE_SIZE, flags); >>>> + mem = kmalloc(alloc_size, flags); >>>> if (!mem) >>>> return -ENOMEM; >>>> >>>> @@ -499,14 +500,16 @@ int hv_common_cpu_init(unsigned int cpu) >>>> } >>>> >>>> if (!ms_hyperv.paravisor_present && >>>> - (hv_isolation_type_snp() || hv_isolation_type_tdx())) { >>>> - ret = set_memory_decrypted((unsigned long)mem, pgcount); >>>> + (hv_isolation_type_snp() || hv_isolation_type_tdx() || >>>> + hv_isolation_type_cca())) { >>> >>> Could this big "if" statement use "hv_is_isolation_supported()" instead >>> of explicitly testing for each CoCo VM type? I ask partly because >>> Mukesh Rathor has just submitted a patch [1] that introduces a new >>> function that does something almost exactly the same as >>> hv_is_isolation_supported() and uses it here. >> >>>> + (hv_isolation_type_snp() || hv_isolation_type_tdx() || >>>> + hv_isolation_type_cca())) { >> >> With my change, this will become: >> >> (hv_isolation_hw_cvm() || hv_isolation_type_cca())) { > > Any reason you wouldn't change hv_isolation_hw_cvm() to > > return hv_isolation_type_snp() || hv_isolation_type_tdx() || > hv_isolation_type_cca() > > That would seem more logical to me. > We could, I just don't know if on cca, the repeat hypercall has same behavior. I was leaving that for the arm team. Anyways, I sent question to the hyp team, if they say yes, i can update my patch to include that. Thanks, -Mukesh