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Wed, 30 Apr 2025 20:01:15 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFZAaGsqWilNG9nKIQwO6WjMhMxoDtCPFtqO+KYQXEgWxu5s0tu5Q6Ot3OxM8Xca9EYb2dyqQ== X-Received: by 2002:a17:903:3c4c:b0:224:256e:5e3f with SMTP id d9443c01a7336-22e040c6e79mr22292615ad.25.1746068475064; Wed, 30 Apr 2025 20:01:15 -0700 (PDT) Received: from [192.168.68.51] ([180.233.125.65]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22e0a243e82sm766515ad.2.2025.04.30.20.01.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 30 Apr 2025 20:01:14 -0700 (PDT) Message-ID: Date: Thu, 1 May 2025 13:01:06 +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 v8 33/43] arm64: RME: Hide KVM_CAP_READONLY_MEM 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: <20250416134208.383984-1-steven.price@arm.com> <20250416134208.383984-34-steven.price@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <20250416134208.383984-34-steven.price@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/16/25 11:41 PM, Steven Price wrote: > For protected memory read only isn't supported by the RMM. While it may > be possible to support read only for unprotected memory, this isn't > supported at the present time. > > Note that this does mean that ROM (or flash) data cannot be emulated > correctly by the VMM as the stage 2 mappings are either always > read/write or are trapped as MMIO (so don't support operations where the > syndrome information doesn't allow emulation, e.g. load/store pair). > > This restriction can be lifted in the future by allowing the stage 2 > mappings to be made read only. > > Signed-off-by: Steven Price > --- > Changes since v7: > * Updated commit message to spell out the impact on ROM/flash > emulation. > --- > arch/arm64/kvm/arm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > Reviewed-by: Gavin Shan