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Fri, 13 Nov 2026 18:59:22 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 4E87620B7166 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1794625162; bh=NFb5ad8hqnTsa2E6F7F8LTT0h034t3fTlgBrnOuiBrM=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=QKdw25zNLEF8biGlipcQuqc/Hf1v1XGVvzmujIgi4qbe3v2Bp/stJfgVpyyz1S0n+ 5dqCxUmzoCa1rvBmYCH5orTcGYkqe3PYhlJk/aDZTQz9e/RxEPIFdByDG+wvr4jY0+ gs1ssnMjFukTLsx9LHA1LY2agRF4FzOuDcZbn8bw= Message-ID: <7ebf7187-bf42-fc11-e89b-b1aba96539d2@linux.microsoft.com> Date: Fri, 13 Nov 2026 18:59:26 -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 From: Mukesh R 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> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/12/26 16:46, Mukesh R wrote: > 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 Confirming, arm has same behavior and needs the fix also. So, we can def expand the check to include _cca. I just sent V1, renaming hv_isolation_hw_cvm() to hv_isolation_type_hw(). If your patch goes after mine, you just need to add to your 0004*: diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c index 4fdc26ade1d7..67a16b4d2235 100644 --- a/arch/arm64/hyperv/mshyperv.c +++ b/arch/arm64/hyperv/mshyperv.c @@ -134,3 +134,8 @@ bool hv_is_hyperv_initialized(void) return hyperv_initialized; } EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized); + +bool hv_isolation_type_hw(void) +{ + return is_realm_world(); +} OR, you could pick mine 0001-* and make it part of your series, and I can drop it from mine and make it dependent on yours. But mine is small enough that it has higher chances of going in first..... Thanks, -Mukesh