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Sat, 01 Feb 2025 18:15:59 -0800 (PST) X-Google-Smtp-Source: AGHT+IGwN4JpbwAKVJUbVg+/34hGwQp5HKYXpKcr/Eo2PO+gIzPd+r9+tV930pBIODwVO11f1VYIuw== X-Received: by 2002:aa7:8c43:0:b0:72f:f86d:c543 with SMTP id d2e1a72fcca58-72ff86dc5cfmr9769126b3a.9.1738462559318; Sat, 01 Feb 2025 18:15:59 -0800 (PST) Received: from [192.168.68.55] ([180.233.125.64]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72fe69ba47esm5834225b3a.96.2025.02.01.18.15.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 01 Feb 2025 18:15:58 -0800 (PST) Message-ID: Date: Sun, 2 Feb 2025 12:15:51 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 25/43] arm64: Don't expose stolen time for realm guests To: Steven Price , kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" References: <20241212155610.76522-1-steven.price@arm.com> <20241212155610.76522-26-steven.price@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <20241212155610.76522-26-steven.price@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/13/24 1:55 AM, Steven Price wrote: > It doesn't make much sense as a realm guest wouldn't want to trust the > host. It will also need some extra work to ensure that KVM will only > attempt to write into a shared memory region. So for now just disable > it. > > Reviewed-by: Suzuki K Poulose > Signed-off-by: Steven Price > --- > arch/arm64/kvm/arm.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index eff1a4ec892b..134acb4ee26f 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -432,7 +432,10 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > r = system_supports_mte(); > break; > case KVM_CAP_STEAL_TIME: > - r = kvm_arm_pvtime_supported(); > + if (kvm_is_realm(kvm)) > + r = 0; > + else > + r = kvm_arm_pvtime_supported(); > break; kvm_vm_ioctl_check_extension() can be called on the file descriptor of "/dev/kvm". 'kvm' is NULL and kvm_is_realm() returns false, which is the missed corner case. > case KVM_CAP_ARM_EL1_32BIT: > r = cpus_have_final_cap(ARM64_HAS_32BIT_EL1); Thanks, Gavin